add: go back button in rankings

add: docker compose code
add: dockerfile and docker ignore rules
2026-03-23 03:05:44 -07:00 · 2026-03-23 02:50:30 -07:00 · 2026-03-23 02:46:53 -07:00 · 2026-03-23 02:40:49 -07:00 · 2026-03-22 21:18:49 -07:00 · 2026-03-22 20:33:29 -07:00
18 changed files with 2689 additions and 58 deletions
--- a/.dockerignore
+++ b/.dockerignore
@@ -0,0 +1,4 @@
+.DS_Store
+.git
+.runtime
+node_modules
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 .DS_Store
 node_modules/
+.runtime/
--- a/15
+++ b/15
@@ -0,0 +1,15 @@
+FROM node:22-bookworm-slim
+
+WORKDIR /app
+
+COPY package.json package-lock.json ./
+RUN npm ci --omit=dev
+
+COPY . .
+
+ENV HOST=0.0.0.0
+ENV PORT=80
+
+EXPOSE 80
+
+CMD ["npm", "start"]
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@

 Static photo gallery for logging meals and food memories.

-The site is based on the HTML5 UP Lens template and currently ships as a plain static site: HTML, CSS, JavaScript, and local image assets.
+The site is based on the HTML5 UP Lens template. The front-end remains a mostly static HTML/CSS/JavaScript site, and the local Node server now also exposes a tiny rankings sync API for shared Elo persistence.

 ## Repo Layout

@@ -16,11 +16,51 @@ The site is based on the HTML5 UP Lens template and currently ships as a plain s
 - `data/meals.json`: source of truth for gallery entries
 - `data/elo.json`: Elo ratings, record totals, and ranking settings
 - `scripts/build.js`: renders static pages from templates and data
+- `scripts/check.js`: validates data, image assets, and generated pages
 - `scripts/generate-thumbnails.js`: regenerates thumbnails from the full-size images
 - `scripts/ingest-meal.js`: ingests a new meal image and metadata in one command
+- `scripts/serve.js`: serves the generated site and the rankings sync API
 - `scripts/lib/elo.js`: validates and syncs Elo data against the meal list
+- `scripts/lib/rankings-state.js`: normalizes and persists the shared rankings state
 - `package.json`: minimal Node build entrypoint

+## Run Locally
+
+Install dependencies:
+
+```sh
+npm install
+```
+
+Build the site and validate the generated output:
+
+```sh
+npm run build
+```
+
+Serve it locally:
+
+```sh
+npm run serve
+```
+
+Then open `http://127.0.0.1:4321`.
+
+By default, rankings sync state is written to `.runtime/rankings-state.json`.
+Override that path with `RANKINGS_STATE_PATH=/absolute/path/to/rankings-state.json`.
+
+If you want a single command that builds and serves, run:
+
+```sh
+npm start
+```
+
+To validate the repo state without rebuilding thumbnails or pages, run:
+
+```sh
+npm run check
+```
+
 ## Content Workflow

 Gallery entries live in `data/meals.json`, and the build generates both `index.html` and `rankings.html` from the template and data files.
@@ -61,6 +101,59 @@ npm run build:thumbs:force
 `data/elo.json` stores the seed rating, Elo `kFactor`, and a win-loss record for each meal.
 The page build keeps this file aligned with `data/meals.json`, so new meals automatically appear in `rankings.html` with the default seed rating.

+The interactive voting flow on `rankings.html` now prefers the same-origin API exposed by `scripts/serve.js`:
+
+- `GET /api/rankings`: load the shared rankings state
+- `POST /api/rankings/vote`: apply one head-to-head result on the server
+- `POST /api/rankings/reset`: reset the shared board back to the seeded state
+
+The server persists the shared board to `.runtime/rankings-state.json` by default, or to `RANKINGS_STATE_PATH` if you set it.
+That makes rankings persist across reloads, sessions, browsers, and devices as long as they are hitting the same deployed site.
+
+If the API is unavailable, the page falls back to browser `localStorage`.
+In that fallback mode, votes still persist across reloads in the same browser profile, but they do not sync across browsers or devices.
+Use the reset button on the rankings page if you want to clear the current saved board and go back to the seeded state.
+
+## Deployment Notes
+
+For Docker/VPS deployment, mount a persistent volume and point `RANKINGS_STATE_PATH` at it so rankings survive container rebuilds and restarts.
+
+Example:
+
+```sh
+RANKINGS_STATE_PATH=/data/rankings-state.json npm start
+```
+
+In a containerized setup, mount `/data` as a named volume or bind mount.
+If you reverse-proxy the app through Caddy on the same domain, the rankings page will use the shared API automatically with no extra CORS setup.
+
+The current server deployment lives one directory up from this repo in `~/docker/websites/docker-compose.yml` and uses this `gallery` service definition:
+
+```yaml
+services:
+  gallery:
+    build:
+      context: ./gallery-src
+    container_name: gallery
+    environment:
+      HOST: 0.0.0.0
+      PORT: 80
+      RANKINGS_STATE_PATH: /data/rankings-state.json
+    volumes:
+      - gallery-rankings:/data
+    restart: unless-stopped
+    networks:
+      - web
+
+networks:
+  web:
+    external: true
+    name: web
+
+volumes:
+  gallery-rankings:
+```
+
 ## Image Conventions

 - Full-size images and thumbnails share the same numeric ID
@@ -91,8 +184,3 @@ For images that should crop away from the center, add optional thumbnail focus m
 ```

 The `x` and `y` values are normalized from `0` to `1`, where `0.5, 0.5` is the center of the image.
-
-## Planned Features
-
-1. A pairwise voting page that shows two food images at a time and updates Elo rankings based on the selected winner.
-2. General cleanup and history cleanup once the bigger structural changes are in place.
--- a/assets/css/rankings.css
+++ b/assets/css/rankings.css
@@ -42,6 +42,186 @@ body.rankings-page #giftwo {
    transform: none;
 }

+#voting {
+    padding: 0 2.25rem 1.75rem 2.25rem;
+}
+
+.voting-panel {
+    background:
+        linear-gradient(140deg, rgba(255, 255, 255, 0.97), rgba(240, 248, 247, 0.94));
+    border: 1px solid rgba(16, 16, 16, 0.08);
+    border-radius: 1.5rem;
+    box-shadow: 0 1.75rem 3.5rem rgba(16, 16, 16, 0.08);
+    padding: 1.5rem;
+}
+
+.voting-panel__intro h2,
+.voting-panel__intro p {
+    margin: 0;
+}
+
+.voting-panel__eyebrow {
+    color: #00a892;
+    font-size: 0.8rem;
+    letter-spacing: 0.12em;
+    margin-bottom: 0.75rem;
+    text-transform: uppercase;
+}
+
+.voting-panel__intro h2 {
+    color: #333;
+    font-size: 2rem;
+}
+
+.vote-status {
+    color: #666;
+    margin-top: 0.5rem;
+}
+
+.voting-panel__actions {
+    display: flex;
+    flex-wrap: wrap;
+    gap: 0.75rem;
+    margin-top: 1.25rem;
+}
+
+.vote-message {
+    color: #333;
+    font-size: 0.95rem;
+    margin: 1rem 0 0 0;
+}
+
+.duel-grid {
+    display: grid;
+    gap: 1rem;
+    grid-template-columns: repeat(2, minmax(0, 1fr));
+    margin-top: 1.25rem;
+}
+
+.duel-placeholder {
+    color: #666;
+    grid-column: 1 / -1;
+    margin: 0;
+}
+
+.duel-card {
+    background: #ffffff;
+    border: 1px solid rgba(16, 16, 16, 0.08);
+    border-radius: 1.25rem;
+    box-shadow: 0 1rem 2.5rem rgba(16, 16, 16, 0.08);
+    display: flex;
+    flex-direction: column;
+    overflow: hidden;
+}
+
+.duel-card__button {
+    background: transparent;
+    border: 0;
+    color: inherit;
+    cursor: pointer;
+    display: block;
+    padding: 0;
+    text-align: left;
+    white-space: normal;
+    width: 100%;
+}
+
+.duel-card__button:hover,
+.duel-card__button:focus-visible {
+    color: inherit;
+}
+
+.duel-card__button:focus-visible {
+    outline: 3px solid rgba(0, 211, 183, 0.55);
+    outline-offset: -3px;
+}
+
+.duel-card__button:hover .duel-card__media img,
+.duel-card__button:focus-visible .duel-card__media img {
+    transform: scale(1.02);
+}
+
+.duel-card__media {
+    background: #eff3f8;
+    overflow: hidden;
+}
+
+.duel-card__media img {
+    aspect-ratio: 3 / 4;
+    display: block;
+    object-fit: cover;
+    transition: transform 0.2s ease;
+    width: 100%;
+}
+
+.duel-card__body {
+    display: flex;
+    flex-direction: column;
+    gap: 0.7rem;
+    padding: 1.25rem;
+}
+
+.duel-card__label,
+.duel-card__meta,
+.duel-card__description,
+.duel-card__body h3 {
+    margin: 0;
+}
+
+.duel-card__label,
+.duel-card__meta {
+    text-transform: uppercase;
+}
+
+.duel-card__label {
+    color: #00a892;
+    font-size: 0.78rem;
+    letter-spacing: 0.12em;
+}
+
+.duel-card__title {
+    color: #333;
+    font-size: 1.5rem;
+}
+
+.duel-card__meta {
+    color: #666;
+    font-size: 0.78rem;
+    letter-spacing: 0.08em;
+}
+
+.duel-card__description {
+    color: #777;
+}
+
+.duel-card__cta {
+    color: #101010;
+    display: inline-flex;
+    font-size: 0.92rem;
+    font-weight: 700;
+    margin-top: 0.35rem;
+}
+
+.duel-card__open {
+    align-self: flex-start;
+    border-bottom: 0;
+    color: #666;
+    font-size: 0.82rem;
+    letter-spacing: 0.08em;
+    margin: 0 1.25rem 1.25rem 1.25rem;
+    text-transform: uppercase;
+}
+
+.duel-card__open:hover {
+    color: #00a892;
+}
+
+.vote-hint {
+    color: #666;
+    font-size: 0.85rem;
+    margin: 1rem 0 0 0;
+}
+
 #rankings-summary {
    padding: 0 2.25rem 1.25rem 2.25rem;
 }
@@ -138,6 +318,7 @@ body.rankings-page #giftwo {
    }

    #rankings-summary,
+    #voting,
    #rankings,
    body.rankings-page #header,
    body.rankings-page #footer {
@@ -145,6 +326,14 @@ body.rankings-page #giftwo {
        padding-right: 1.25rem;
    }

+    .voting-panel {
+        padding: 1.25rem;
+    }
+
+    .duel-grid {
+        grid-template-columns: 1fr;
+    }
+
    .ranking-card {
        grid-template-columns: 1fr;
    }
--- a/assets/js/rankings.js
+++ b/assets/js/rankings.js
@@ -0,0 +1,956 @@
+(function () {
+  const STORAGE_KEY = "gallery.rankings.v1";
+  const STORAGE_TEST_KEY = `${STORAGE_KEY}.probe`;
+  const STATE_VERSION = 1;
+  const CLOSE_MATCH_COUNT = 6;
+  const REMOTE_RANKINGS_URL = "/api/rankings";
+  const REMOTE_RANKINGS_VOTE_URL = "/api/rankings/vote";
+  const REMOTE_RANKINGS_RESET_URL = "/api/rankings/reset";
+  const REMOTE_RANKINGS_UNDO_URL = "/api/rankings/undo";
+
+  function $(id) {
+    return document.getElementById(id);
+  }
+
+  function escapeHtml(value) {
+    return String(value)
+      .replace(/&/g, "&amp;")
+      .replace(/</g, "&lt;")
+      .replace(/>/g, "&gt;")
+      .replace(/"/g, "&quot;");
+  }
+
+  function formatRating(rating) {
+    return new Intl.NumberFormat("en-US", {
+      maximumFractionDigits: 0,
+    }).format(rating);
+  }
+
+  function pluralize(count, singular, plural) {
+    return count === 1 ? singular : plural;
+  }
+
+  function createPairKey(leftId, rightId) {
+    return [leftId, rightId].sort().join(":");
+  }
+
+  function isValidMealId(id) {
+    return typeof id === "string" && /^\d+$/.test(id);
+  }
+
+  function createDefaultEntry(id, defaultRating) {
+    return {
+      id,
+      rating: defaultRating,
+      wins: 0,
+      losses: 0,
+    };
+  }
+
+  function cloneEntry(entry) {
+    return {
+      id: entry.id,
+      rating: entry.rating,
+      wins: entry.wins,
+      losses: entry.losses,
+    };
+  }
+
+  function roundRating(rating) {
+    return Math.round(rating * 1000) / 1000;
+  }
+
+  function pickRandom(items) {
+    return items[Math.floor(Math.random() * items.length)];
+  }
+
+  function parseSeedData() {
+    const seedElement = $("rankings-seed-data");
+
+    if (!seedElement) {
+      throw new Error("Missing rankings seed data");
+    }
+
+    const seedData = JSON.parse(seedElement.textContent);
+
+    if (!seedData || !Array.isArray(seedData.meals) || !seedData.elo) {
+      throw new Error("Invalid rankings seed data");
+    }
+
+    return seedData;
+  }
+
+  async function requestJson(url, options) {
+    const response = await fetch(url, {
+      cache: "no-store",
+      headers: {
+        Accept: "application/json",
+        ...(options && options.body ? { "Content-Type": "application/json" } : {}),
+      },
+      ...options,
+    });
+
+    if (!response.ok) {
+      throw new Error(`Request failed with status ${response.status}`);
+    }
+
+    return response.json();
+  }
+
+  function createLocalPersistence() {
+    let available = false;
+
+    try {
+      localStorage.setItem(STORAGE_TEST_KEY, "1");
+      localStorage.removeItem(STORAGE_TEST_KEY);
+      available = true;
+    } catch (error) {
+      available = false;
+    }
+
+    return {
+      get available() {
+        return available;
+      },
+      load() {
+        if (!available) {
+          return null;
+        }
+
+        try {
+          const raw = localStorage.getItem(STORAGE_KEY);
+          return raw ? JSON.parse(raw) : null;
+        } catch (error) {
+          return null;
+        }
+      },
+      save(state) {
+        if (!available) {
+          return;
+        }
+
+        try {
+          localStorage.setItem(STORAGE_KEY, JSON.stringify(state));
+        } catch (error) {
+          available = false;
+        }
+      },
+      clear() {
+        if (!available) {
+          return;
+        }
+
+        try {
+          localStorage.removeItem(STORAGE_KEY);
+        } catch (error) {
+          available = false;
+        }
+      },
+    };
+  }
+
+  function createPersistence() {
+    const local = createLocalPersistence();
+    let mode = "memory";
+    let pendingNotice = null;
+
+    function setMode(nextMode, nextNotice) {
+      if (mode !== nextMode && nextNotice) {
+        pendingNotice = nextNotice;
+      }
+
+      mode = nextMode;
+    }
+
+    function getFallbackMode() {
+      return local.available ? "local" : "memory";
+    }
+
+    return {
+      get mode() {
+        return mode;
+      },
+      async load(seedData) {
+        if (typeof fetch === "function") {
+          try {
+            const remoteState = await requestJson(REMOTE_RANKINGS_URL, { method: "GET" });
+
+            setMode("server");
+
+            return syncStoredState(seedData, remoteState);
+          } catch (error) {
+            setMode(getFallbackMode());
+          }
+        } else {
+          setMode(getFallbackMode());
+        }
+
+        return syncStoredState(seedData, local.load());
+      },
+      async save(state) {
+        if (mode === "local") {
+          local.save(state);
+        }
+
+        return state;
+      },
+      async submitVote(seedData, state, winnerId, loserId, pairKey, leftId, rightId) {
+        if (mode === "server" && typeof fetch === "function") {
+          try {
+            const remoteState = await requestJson(REMOTE_RANKINGS_VOTE_URL, {
+              method: "POST",
+              body: JSON.stringify({
+                winnerId,
+                loserId,
+                pairKey,
+                leftId,
+                rightId,
+              }),
+            });
+
+            return syncStoredState(seedData, remoteState);
+          } catch (error) {
+            setMode(
+              getFallbackMode(),
+              local.available
+                ? "Server sync failed, so votes are now saved only in this browser."
+                : "Server sync failed, so votes will reset when you reload."
+            );
+          }
+        }
+
+        const nextState = applyVote(
+          seedData,
+          state,
+          winnerId,
+          loserId,
+          pairKey,
+          leftId,
+          rightId
+        );
+
+        if (mode === "local") {
+          local.save(nextState);
+        }
+
+        return nextState;
+      },
+      async undo(seedData, state) {
+        if (mode === "server" && typeof fetch === "function") {
+          try {
+            const remoteState = await requestJson(REMOTE_RANKINGS_UNDO_URL, {
+              method: "POST",
+            });
+
+            return syncStoredState(seedData, remoteState);
+          } catch (error) {
+            setMode(
+              getFallbackMode(),
+              local.available
+                ? "Server sync failed, so go back now applies only in this browser."
+                : "Server sync failed, so go back lasts only until you reload."
+            );
+          }
+        }
+
+        const nextState = undoLastVote(seedData, state);
+
+        if (mode === "local") {
+          local.save(nextState);
+        }
+
+        return nextState;
+      },
+      async reset(seedData) {
+        if (mode === "server" && typeof fetch === "function") {
+          try {
+            const remoteState = await requestJson(REMOTE_RANKINGS_RESET_URL, {
+              method: "POST",
+            });
+
+            return syncStoredState(seedData, remoteState);
+          } catch (error) {
+            setMode(
+              getFallbackMode(),
+              local.available
+                ? "Server sync failed, so resets now apply only in this browser."
+                : "Server sync failed, so resets last only until you reload."
+            );
+          }
+        }
+
+        const nextState = createSeedState(seedData);
+
+        if (mode === "local") {
+          local.clear();
+          local.save(nextState);
+        }
+
+        return nextState;
+      },
+      consumeNotice() {
+        const notice = pendingNotice;
+
+        pendingNotice = null;
+
+        return notice;
+      },
+    };
+  }
+
+  function isValidStoredEntry(entry) {
+    if (!entry || typeof entry !== "object" || Array.isArray(entry)) {
+      return false;
+    }
+
+    if (typeof entry.id !== "string" || !/^\d+$/.test(entry.id)) {
+      return false;
+    }
+
+    if (typeof entry.rating !== "number" || !Number.isFinite(entry.rating) || entry.rating <= 0) {
+      return false;
+    }
+
+    return ["wins", "losses"].every(
+      (field) => Number.isInteger(entry[field]) && entry[field] >= 0
+    );
+  }
+
+  function createSeedState(seedData) {
+    return {
+      version: STATE_VERSION,
+      voteCount: 0,
+      lastPairKey: null,
+      updatedAt: null,
+      undo: null,
+      elo: {
+        defaultRating: seedData.elo.defaultRating,
+        kFactor: seedData.elo.kFactor,
+        entries: seedData.meals.map((meal) => {
+          const seedEntry =
+            seedData.elo.entries.find((entry) => entry.id === meal.id) ||
+            createDefaultEntry(meal.id, seedData.elo.defaultRating);
+
+          return cloneEntry(seedEntry);
+        }),
+      },
+    };
+  }
+
+  function syncStateCore(seedData, storedState) {
+    if (!storedState || typeof storedState !== "object" || Array.isArray(storedState)) {
+      return createSeedState(seedData);
+    }
+
+    const storedEntries = Array.isArray(storedState.elo?.entries)
+      ? storedState.elo.entries.filter(isValidStoredEntry)
+      : [];
+    const storedEntryById = new Map(storedEntries.map((entry) => [entry.id, entry]));
+    const seedEntryById = new Map(seedData.elo.entries.map((entry) => [entry.id, entry]));
+    const entries = seedData.meals.map((meal) => {
+      const storedEntry = storedEntryById.get(meal.id);
+
+      if (storedEntry) {
+        return cloneEntry(storedEntry);
+      }
+
+      const seedEntry =
+        seedEntryById.get(meal.id) || createDefaultEntry(meal.id, seedData.elo.defaultRating);
+
+      return cloneEntry(seedEntry);
+    });
+    const derivedVoteCount = entries.reduce((sum, entry) => sum + entry.wins, 0);
+
+    return {
+      version: STATE_VERSION,
+      voteCount:
+        Number.isInteger(storedState.voteCount) && storedState.voteCount >= derivedVoteCount
+          ? storedState.voteCount
+          : derivedVoteCount,
+      lastPairKey: typeof storedState.lastPairKey === "string" ? storedState.lastPairKey : null,
+      updatedAt: typeof storedState.updatedAt === "string" ? storedState.updatedAt : null,
+      undo: null,
+      elo: {
+        defaultRating: seedData.elo.defaultRating,
+        kFactor: seedData.elo.kFactor,
+        entries,
+      },
+    };
+  }
+
+  function createUndoSnapshot(state) {
+    return {
+      voteCount: state.voteCount,
+      lastPairKey: state.lastPairKey,
+      updatedAt: state.updatedAt,
+      elo: {
+        defaultRating: state.elo.defaultRating,
+        kFactor: state.elo.kFactor,
+        entries: state.elo.entries.map(cloneEntry),
+      },
+    };
+  }
+
+  function resolveUndoPairIds(winnerId, loserId, leftId, rightId) {
+    const validPair =
+      isValidMealId(leftId) &&
+      isValidMealId(rightId) &&
+      leftId !== rightId &&
+      [leftId, rightId].includes(winnerId) &&
+      [leftId, rightId].includes(loserId);
+
+    if (validPair) {
+      return { leftId, rightId };
+    }
+
+    return { leftId: winnerId, rightId: loserId };
+  }
+
+  function syncUndo(seedData, storedUndo) {
+    if (!storedUndo || typeof storedUndo !== "object" || Array.isArray(storedUndo)) {
+      return null;
+    }
+
+    const { leftId, rightId, winnerId, loserId, snapshot } = storedUndo;
+
+    if (
+      !isValidMealId(leftId) ||
+      !isValidMealId(rightId) ||
+      !isValidMealId(winnerId) ||
+      !isValidMealId(loserId) ||
+      leftId === rightId ||
+      winnerId === loserId
+    ) {
+      return null;
+    }
+
+    const pairIds = new Set([leftId, rightId]);
+    const mealIds = new Set(seedData.meals.map((meal) => meal.id));
+
+    if (
+      !pairIds.has(winnerId) ||
+      !pairIds.has(loserId) ||
+      ![leftId, rightId, winnerId, loserId].every((id) => mealIds.has(id))
+    ) {
+      return null;
+    }
+
+    return {
+      pairKey: createPairKey(leftId, rightId),
+      leftId,
+      rightId,
+      winnerId,
+      loserId,
+      snapshot: createUndoSnapshot(syncStateCore(seedData, snapshot)),
+    };
+  }
+
+  function syncStoredState(seedData, storedState) {
+    const nextState = syncStateCore(seedData, storedState);
+
+    return {
+      ...nextState,
+      undo: syncUndo(seedData, storedState?.undo),
+    };
+  }
+
+  function restoreUndoSnapshot(seedData, snapshot) {
+    return {
+      ...syncStateCore(seedData, snapshot),
+      undo: null,
+    };
+  }
+
+  function compareRankedMeals(left, right) {
+    const leftMatches = left.wins + left.losses;
+    const rightMatches = right.wins + right.losses;
+
+    if (right.rating !== left.rating) {
+      return right.rating - left.rating;
+    }
+
+    if (rightMatches !== leftMatches) {
+      return rightMatches - leftMatches;
+    }
+
+    return Number.parseInt(left.id, 10) - Number.parseInt(right.id, 10);
+  }
+
+  function getRankedMeals(meals, eloData) {
+    const entryById = new Map(eloData.entries.map((entry) => [entry.id, entry]));
+
+    return meals
+      .map((meal) => {
+        const entry =
+          entryById.get(meal.id) || createDefaultEntry(meal.id, eloData.defaultRating);
+
+        return {
+          ...meal,
+          rating: entry.rating,
+          wins: entry.wins,
+          losses: entry.losses,
+          matches: entry.wins + entry.losses,
+        };
+      })
+      .sort(compareRankedMeals);
+  }
+
+  function getRankingMeta(rankedMeal) {
+    const ratingText = `Elo ${formatRating(rankedMeal.rating)}`;
+
+    if (rankedMeal.matches === 0) {
+      return `${ratingText} | no votes yet`;
+    }
+
+    return `${ratingText} | ${rankedMeal.wins}-${rankedMeal.losses} record across ${
+      rankedMeal.matches
+    } ${pluralize(rankedMeal.matches, "match", "matches")}`;
+  }
+
+  function expectedScore(rating, opponentRating) {
+    return 1 / (1 + Math.pow(10, (opponentRating - rating) / 400));
+  }
+
+  function applyVote(seedData, state, winnerId, loserId, pairKey, leftId, rightId) {
+    const entryById = new Map(
+      state.elo.entries.map((entry) => [entry.id, cloneEntry(entry)])
+    );
+    const winner = entryById.get(winnerId);
+    const loser = entryById.get(loserId);
+    const undoPair = resolveUndoPairIds(winnerId, loserId, leftId, rightId);
+    const resolvedPairKey =
+      typeof pairKey === "string" && pairKey.length > 0
+        ? pairKey
+        : createPairKey(undoPair.leftId, undoPair.rightId);
+
+    if (!winner || !loser) {
+      return state;
+    }
+
+    const winnerExpected = expectedScore(winner.rating, loser.rating);
+    const loserExpected = expectedScore(loser.rating, winner.rating);
+
+    winner.rating = roundRating(winner.rating + state.elo.kFactor * (1 - winnerExpected));
+    loser.rating = roundRating(loser.rating + state.elo.kFactor * (0 - loserExpected));
+    winner.wins += 1;
+    loser.losses += 1;
+
+    return {
+      ...state,
+      voteCount: state.voteCount + 1,
+      lastPairKey: resolvedPairKey,
+      updatedAt: new Date().toISOString(),
+      undo: {
+        pairKey: createPairKey(undoPair.leftId, undoPair.rightId),
+        leftId: undoPair.leftId,
+        rightId: undoPair.rightId,
+        winnerId,
+        loserId,
+        snapshot: createUndoSnapshot(state),
+      },
+      elo: {
+        ...state.elo,
+        entries: seedData.meals.map((meal) => entryById.get(meal.id)),
+      },
+    };
+  }
+
+  function undoLastVote(seedData, state) {
+    if (!state.undo) {
+      return state;
+    }
+
+    return restoreUndoSnapshot(seedData, state.undo.snapshot);
+  }
+
+  function choosePair(rankedMeals, avoidedPairKeys) {
+    if (rankedMeals.length < 2) {
+      return null;
+    }
+
+    const avoided = new Set(avoidedPairKeys.filter(Boolean));
+    const rankedOrder = new Map(rankedMeals.map((meal, index) => [meal.id, index]));
+
+    for (let attempt = 0; attempt < 20; attempt += 1) {
+      const baseMeal = rankedMeals[Math.floor(Math.random() * rankedMeals.length)];
+      const candidates = rankedMeals
+        .filter((meal) => meal.id !== baseMeal.id)
+        .sort((left, right) => {
+          const ratingGap = Math.abs(left.rating - baseMeal.rating) - Math.abs(right.rating - baseMeal.rating);
+
+          if (ratingGap !== 0) {
+            return ratingGap;
+          }
+
+          return (
+            Math.abs(rankedOrder.get(left.id) - rankedOrder.get(baseMeal.id)) -
+            Math.abs(rankedOrder.get(right.id) - rankedOrder.get(baseMeal.id))
+          );
+        });
+      const closeCandidates = candidates.slice(0, Math.min(CLOSE_MATCH_COUNT, candidates.length));
+      const filteredCandidates = closeCandidates.filter(
+        (meal) => !avoided.has(createPairKey(baseMeal.id, meal.id))
+      );
+      const candidatePool =
+        filteredCandidates.length > 0
+          ? filteredCandidates
+          : candidates.filter((meal) => !avoided.has(createPairKey(baseMeal.id, meal.id)));
+      const fallbackPool = candidatePool.length > 0 ? candidatePool : candidates;
+      const opponent = pickRandom(
+        fallbackPool.slice(0, Math.min(CLOSE_MATCH_COUNT, fallbackPool.length))
+      );
+
+      if (opponent) {
+        return Math.random() < 0.5
+          ? { left: baseMeal, right: opponent }
+          : { left: opponent, right: baseMeal };
+      }
+    }
+
+    return {
+      left: rankedMeals[0],
+      right: rankedMeals[1],
+    };
+  }
+
+  function renderDuelCard(meal, sideLabel, disabled) {
+    const disabledAttributes = disabled ? ' disabled aria-disabled="true"' : "";
+
+    return `<article class="duel-card">
+      <button class="duel-card__button" type="button" data-meal-id="${meal.id}"${disabledAttributes}>
+        <div class="duel-card__media">
+          <img src="images/fulls/${meal.id}.jpg" alt="${escapeHtml(`${meal.title} photo`)}" />
+        </div>
+        <div class="duel-card__body">
+          <p class="duel-card__label">${escapeHtml(sideLabel)}</p>
+          <h3 class="duel-card__title">${escapeHtml(meal.title)}</h3>
+          <p class="duel-card__meta">${escapeHtml(getRankingMeta(meal))}</p>
+          <p class="duel-card__description">${escapeHtml(meal.description)}</p>
+          <span class="duel-card__cta">Choose this meal</span>
+        </div>
+      </button>
+      <a class="duel-card__open" href="images/fulls/${meal.id}.jpg" target="_blank" rel="noreferrer">open full image</a>
+    </article>`;
+  }
+
+  function renderRankingCard(meal, placement) {
+    return `<article class="ranking-card">
+      <p class="ranking-card__placement">#${placement}</p>
+      <a class="ranking-card__thumbnail" href="images/fulls/${meal.id}.jpg">
+        <img src="images/thumbs/${meal.id}.jpg" alt="${escapeHtml(`${meal.title} thumbnail`)}" loading="lazy" />
+      </a>
+      <div class="ranking-card__body">
+        <h2>${escapeHtml(meal.title)}</h2>
+        <p class="ranking-card__meta">${escapeHtml(getRankingMeta(meal))}</p>
+        <p>${escapeHtml(meal.description)}</p>
+      </div>
+    </article>`;
+  }
+
+  function getSummaryText(seedData, state, persistence) {
+    const voteText = `${state.voteCount} ${pluralize(state.voteCount, "vote", "votes")}`;
+
+    if (persistence.mode === "server") {
+      return `${seedData.meals.length} meals ranked. ${voteText} saved on the server.`;
+    }
+
+    if (persistence.mode === "local") {
+      return `${seedData.meals.length} meals ranked. ${voteText} saved only in this browser.`;
+    }
+
+    return `${seedData.meals.length} meals ranked. ${voteText} active for this session only.`;
+  }
+
+  function getStatusText(persistence) {
+    if (persistence.mode === "server") {
+      return "Votes are saved on the server and shared across browsers.";
+    }
+
+    if (persistence.mode === "local") {
+      return "Server sync is unavailable, so votes are saved only in this browser.";
+    }
+
+    return "Browser storage is unavailable, so votes reset when you reload.";
+  }
+
+  async function init() {
+    let seedData;
+
+    try {
+      seedData = parseSeedData();
+    } catch (error) {
+      console.error(error);
+      return;
+    }
+
+    const elements = {
+      duelCards: $("duel-cards"),
+      rankings: $("rankings"),
+      rankingSummary: document.querySelector("#rankings-summary .ranking-summary"),
+      voteStatus: $("vote-status"),
+      voteMessage: $("vote-message"),
+      skipPair: $("skip-pair"),
+      undoVote: $("undo-vote"),
+      resetRankings: $("reset-rankings"),
+    };
+
+    if (
+      !elements.duelCards ||
+      !elements.rankings ||
+      !elements.rankingSummary ||
+      !elements.voteStatus ||
+      !elements.voteMessage ||
+      !elements.skipPair ||
+      !elements.undoVote ||
+      !elements.resetRankings
+    ) {
+      return;
+    }
+
+    elements.voteMessage.textContent = "Loading saved rankings...";
+
+    const persistence = createPersistence();
+    const mealById = new Map(seedData.meals.map((meal) => [meal.id, meal]));
+    let state = await persistence.load(seedData);
+    let currentPair = null;
+    let currentPairKey = null;
+    let pendingPairIds = null;
+    let lastMessage = "Choose the better meal to start ranking.";
+    let busy = false;
+
+    await persistence.save(state);
+
+    function queueNextPair(rankedMeals) {
+      if (pendingPairIds) {
+        const rankedMealById = new Map(rankedMeals.map((meal) => [meal.id, meal]));
+        const left = rankedMealById.get(pendingPairIds.leftId);
+        const right = rankedMealById.get(pendingPairIds.rightId);
+
+        pendingPairIds = null;
+
+        if (left && right && left.id !== right.id) {
+          currentPair = { left, right };
+          currentPairKey = createPairKey(left.id, right.id);
+          return;
+        }
+      }
+
+      currentPair = choosePair(rankedMeals, [currentPairKey, state.lastPairKey]);
+      currentPairKey = currentPair
+        ? createPairKey(currentPair.left.id, currentPair.right.id)
+        : null;
+    }
+
+    function render(message) {
+      const rankedMeals = getRankedMeals(seedData.meals, state.elo);
+
+      if (message) {
+        lastMessage = message;
+      }
+
+      if (
+        !currentPair ||
+        !rankedMeals.some((meal) => meal.id === currentPair.left.id) ||
+        !rankedMeals.some((meal) => meal.id === currentPair.right.id)
+      ) {
+        queueNextPair(rankedMeals);
+      }
+
+      elements.voteStatus.textContent = getStatusText(persistence);
+      elements.voteMessage.textContent = lastMessage;
+      elements.rankingSummary.textContent = getSummaryText(seedData, state, persistence);
+      elements.undoVote.disabled = busy || !state.undo;
+      elements.resetRankings.disabled = busy;
+      elements.rankings.innerHTML = rankedMeals
+        .map((meal, index) => renderRankingCard(meal, index + 1))
+        .join("");
+
+      if (!currentPair) {
+        elements.duelCards.innerHTML =
+          '<p class="duel-placeholder">Add at least two meals before starting head-to-head voting.</p>';
+        elements.skipPair.disabled = true;
+        return;
+      }
+
+      elements.skipPair.disabled = busy;
+      elements.duelCards.innerHTML = [
+        renderDuelCard(currentPair.left, "Left Pick", busy),
+        renderDuelCard(currentPair.right, "Right Pick", busy),
+      ].join("");
+    }
+
+    async function handleVote(winnerId) {
+      if (!currentPair || busy) {
+        return;
+      }
+
+      const loserId = currentPair.left.id === winnerId ? currentPair.right.id : currentPair.left.id;
+      const winnerTitle =
+        currentPair.left.id === winnerId ? currentPair.left.title : currentPair.right.title;
+      const loserTitle =
+        currentPair.left.id === winnerId ? currentPair.right.title : currentPair.left.title;
+      let nextMessage = `Picked ${winnerTitle} over ${loserTitle}.`;
+
+      busy = true;
+      render(`Saving ${winnerTitle} over ${loserTitle}...`);
+
+      try {
+        state = await persistence.submitVote(
+          seedData,
+          state,
+          winnerId,
+          loserId,
+          currentPairKey,
+          currentPair.left.id,
+          currentPair.right.id
+        );
+        currentPair = null;
+
+        const notice = persistence.consumeNotice();
+
+        if (notice) {
+          nextMessage = `${nextMessage} ${notice}`;
+        }
+      } catch (error) {
+        console.error(error);
+        nextMessage = "Failed to save that vote.";
+      } finally {
+        busy = false;
+        render(nextMessage);
+      }
+    }
+
+    async function handleUndo() {
+      if (!state.undo || busy) {
+        return;
+      }
+
+      const undoInfo = state.undo;
+      const winnerTitle = mealById.get(undoInfo.winnerId)?.title || "that meal";
+      const loserTitle = mealById.get(undoInfo.loserId)?.title || "the other meal";
+      let nextMessage = `Went back before ${winnerTitle} over ${loserTitle}. Pick again.`;
+
+      busy = true;
+      render(`Going back before ${winnerTitle} over ${loserTitle}...`);
+
+      try {
+        state = await persistence.undo(seedData, state);
+        currentPair = null;
+        currentPairKey = null;
+        pendingPairIds = {
+          leftId: undoInfo.leftId,
+          rightId: undoInfo.rightId,
+        };
+
+        const notice = persistence.consumeNotice();
+
+        if (notice) {
+          nextMessage = `${nextMessage} ${notice}`;
+        }
+      } catch (error) {
+        console.error(error);
+        nextMessage = "Failed to go back to the previous vote.";
+      } finally {
+        busy = false;
+        render(nextMessage);
+      }
+    }
+
+    elements.duelCards.addEventListener("click", async (event) => {
+      const button = event.target.closest("[data-meal-id]");
+
+      if (!button) {
+        return;
+      }
+
+      await handleVote(button.getAttribute("data-meal-id"));
+    });
+
+    elements.skipPair.addEventListener("click", () => {
+      if (busy) {
+        return;
+      }
+
+      const rankedMeals = getRankedMeals(seedData.meals, state.elo);
+
+      queueNextPair(rankedMeals);
+      render("Skipped that pair.");
+    });
+
+    elements.undoVote.addEventListener("click", async () => {
+      await handleUndo();
+    });
+
+    elements.resetRankings.addEventListener("click", async () => {
+      if (busy) {
+        return;
+      }
+
+      if (!window.confirm("Reset the saved rankings back to the seeded board?")) {
+        return;
+      }
+
+      let nextMessage = "Saved rankings cleared. Back to the seeded board.";
+
+      busy = true;
+      render("Resetting saved rankings...");
+
+      try {
+        state = await persistence.reset(seedData);
+        currentPair = null;
+        currentPairKey = null;
+
+        const notice = persistence.consumeNotice();
+
+        if (notice) {
+          nextMessage = `${nextMessage} ${notice}`;
+        }
+      } catch (error) {
+        console.error(error);
+        nextMessage = "Failed to reset rankings.";
+      } finally {
+        busy = false;
+        render(nextMessage);
+      }
+    });
+
+    document.addEventListener("keydown", async (event) => {
+      const target = event.target;
+
+      if (
+        target &&
+        ["INPUT", "TEXTAREA", "SELECT", "BUTTON"].includes(target.tagName)
+      ) {
+        return;
+      }
+
+      if (busy) {
+        return;
+      }
+
+      if (event.key.toLowerCase() === "z" && state.undo) {
+        event.preventDefault();
+        await handleUndo();
+        return;
+      }
+
+      if (!currentPair) {
+        return;
+      }
+
+      if (event.key === "ArrowLeft") {
+        event.preventDefault();
+        await handleVote(currentPair.left.id);
+      } else if (event.key === "ArrowRight") {
+        event.preventDefault();
+        await handleVote(currentPair.right.id);
+      }
+    });
+
+    render();
+  }
+
+  init().catch((error) => {
+    console.error(error);
+  });
+})();
--- a/images/thumbs/.thumbs-manifest.json
+++ b/images/thumbs/.thumbs-manifest.json
@@ -4,7 +4,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500129000,
+    "mtimeMs": 1774257676921.0168,
    "size": 1052830,
    "focus": {
      "x": 0.35,
@@ -16,7 +16,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676923.4688,
    "size": 835360,
    "focus": null
  },
@@ -25,7 +25,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676926.1216,
    "size": 1034158,
    "focus": {
      "x": 0.5,
@@ -37,7 +37,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676928.9744,
    "size": 1090215,
    "focus": null
  },
@@ -46,7 +46,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676931.93,
    "size": 1122236,
    "focus": {
      "x": 0.5,
@@ -58,7 +58,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770444049000,
+    "mtimeMs": 1774257676932.7878,
    "size": 676787,
    "focus": null
  },
@@ -67,7 +67,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676935.0764,
    "size": 872024,
    "focus": null
  },
@@ -76,7 +76,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676936.637,
    "size": 618276,
    "focus": null
  },
@@ -85,7 +85,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500127000,
+    "mtimeMs": 1774257676938.8577,
    "size": 1349804,
    "focus": null
  },
@@ -94,7 +94,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676940.0383,
    "size": 1071870,
    "focus": null
  },
@@ -103,7 +103,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676941.5466,
    "size": 764329,
    "focus": null
  },
@@ -112,7 +112,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676943.8735,
    "size": 1172905,
    "focus": null
  },
@@ -121,7 +121,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500129000,
+    "mtimeMs": 1774257676945.2588,
    "size": 1099540,
    "focus": null
  },
@@ -130,7 +130,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676946.2732,
    "size": 1052362,
    "focus": null
  },
@@ -139,7 +139,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676947.5552,
    "size": 1227608,
    "focus": null
  },
@@ -148,7 +148,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500127000,
+    "mtimeMs": 1774257676949.5437,
    "size": 840466,
    "focus": null
  },
@@ -157,7 +157,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676951.916,
    "size": 1136990,
    "focus": null
  },
@@ -166,7 +166,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500127000,
+    "mtimeMs": 1774257676954.4558,
    "size": 1261294,
    "focus": null
  },
@@ -175,7 +175,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676956.7886,
    "size": 1119498,
    "focus": null
  },
@@ -184,7 +184,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676958.691,
    "size": 868085,
    "focus": null
  },
@@ -193,7 +193,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676961.0393,
    "size": 1057896,
    "focus": null
  },
@@ -202,7 +202,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676963.4336,
    "size": 1088795,
    "focus": null
  },
@@ -211,7 +211,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500129000,
+    "mtimeMs": 1774257676965.364,
    "size": 852307,
    "focus": null
  },
@@ -220,7 +220,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500129000,
+    "mtimeMs": 1774257676967.8005,
    "size": 1149955,
    "focus": null
  },
@@ -229,7 +229,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500129000,
+    "mtimeMs": 1774257676970.2761,
    "size": 1242099,
    "focus": null
  },
@@ -238,7 +238,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676971.9075,
    "size": 1414024,
    "focus": null
  },
@@ -247,7 +247,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676973.2812,
    "size": 1022877,
    "focus": null
  },
@@ -256,7 +256,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500129000,
+    "mtimeMs": 1774257676974.2112,
    "size": 1018868,
    "focus": null
  },
@@ -265,7 +265,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500128000,
+    "mtimeMs": 1774257676975.1504,
    "size": 1233602,
    "focus": null
  },
@@ -274,7 +274,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1770500129000,
+    "mtimeMs": 1774257676976.6533,
    "size": 739786,
    "focus": null
  },
@@ -283,7 +283,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1771126436000,
+    "mtimeMs": 1774257676977.1958,
    "size": 1069693,
    "focus": null
  },
@@ -292,7 +292,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1771226059000,
+    "mtimeMs": 1774257676979.063,
    "size": 995282,
    "focus": null
  },
@@ -301,7 +301,7 @@
    "width": 240,
    "height": 320,
    "quality": 82,
-    "mtimeMs": 1771226144000,
+    "mtimeMs": 1774257676980.472,
    "size": 729224,
    "focus": null
  }
--- a/index.html
+++ b/index.html
@@ -30,9 +30,9 @@
 				<h1>for vham :3</h1>
 				<p id="haiku">Please enable javascript >.<</p>
 				<p class="page-links">
-					<a href="index.html" aria-current="page">gallery</a>
+					<a href="./" aria-current="page">gallery</a>
 					<span class="page-links__separator">/</span>
-					<a href="rankings.html">rankings</a>
+					<a href="rankings">rankings</a>
 				</p>
 			</header>

--- a/package.json
+++ b/package.json
@@ -2,11 +2,14 @@
  "name": "gallery",
  "private": true,
  "scripts": {
-    "build": "npm run build:thumbs && npm run build:pages",
+    "build": "npm run build:thumbs && npm run build:pages && npm run check",
    "ingest": "node scripts/ingest-meal.js",
+    "check": "node scripts/check.js",
    "build:pages": "node scripts/build.js",
    "build:thumbs": "node scripts/generate-thumbnails.js",
-    "build:thumbs:force": "node scripts/generate-thumbnails.js --force"
+    "build:thumbs:force": "node scripts/generate-thumbnails.js --force",
+    "serve": "node scripts/serve.js",
+    "start": "npm run build && npm run serve"
  },
  "dependencies": {
    "sharp": "^0.34.5"
--- a/rankings.html
+++ b/rankings.html
@@ -28,17 +28,38 @@
 			<header id="header">
 				<img src="images/meow.gif" alt="meow" id="gifone">
 				<h1>food power rankings</h1>
-				<p>static Elo seeds for every meal before the head-to-head voting page exists.</p>
+				<p>pick the better meal, one pair at a time, and the board updates live in this browser.</p>
 				<p class="page-links">
-					<a href="index.html">gallery</a>
+					<a href="./">gallery</a>
 					<span class="page-links__separator">/</span>
-					<a href="rankings.html" aria-current="page">rankings</a>
+					<a href="rankings" aria-current="page">rankings</a>
 				</p>
 			</header>

+			<!-- Voting -->
+			<section id="voting">
+				<div class="voting-panel">
+					<div class="voting-panel__intro">
+						<p class="voting-panel__eyebrow">Head-To-Head Voting</p>
+						<h2>Pick the winner.</h2>
+						<p class="vote-status" id="vote-status" aria-live="polite">Enable JavaScript to load saved rankings.</p>
+					</div>
+					<div class="voting-panel__actions">
+						<button class="button small" id="skip-pair" type="button">skip pair</button>
+						<button class="button small" id="undo-vote" type="button">go back</button>
+						<button class="button small" id="reset-rankings" type="button">reset saved rankings</button>
+					</div>
+					<p class="vote-message" id="vote-message" aria-live="polite">Enable JavaScript to load head-to-head voting.</p>
+					<div class="duel-grid" id="duel-cards">
+						<p class="duel-placeholder">Enable JavaScript to compare meals here.</p>
+					</div>
+					<p class="vote-hint">Tip: use the left and right arrow keys to vote faster, or press Z to go back.</p>
+				</div>
+			</section>
+
 			<!-- Rankings Summary -->
 			<section id="rankings-summary">
-				<p class="ranking-summary">33 meals seeded at Elo 1,000 until head-to-head voting starts.</p>
+				<p class="ranking-summary">33 meals seeded at Elo 1,000. Enable JavaScript to vote and reorder them.</p>
 			</section>

 			<!-- Rankings -->
@@ -351,5 +372,402 @@
 			</footer>

 		</div>
+		<script id="rankings-seed-data" type="application/json">
+			{
+			  "meals": [
+			    {
+			      "id": "01",
+			      "thumbnail": {
+			        "focus": {
+			          "x": 0.35,
+			          "y": 0.5
+			        }
+			      },
+			      "position": "left center",
+			      "title": "sf on $10",
+			      "description": "this was so not real i can't believe technically u paid for our first meal back. calmluh 3 years after. first hang !!!! pork buns were yummy 7/10"
+			    },
+			    {
+			      "id": "02",
+			      "title": "honey butter chicken",
+			      "description": "the first thing you cooked for me ! so yum 10/10"
+			    },
+			    {
+			      "id": "03",
+			      "thumbnail": {
+			        "focus": {
+			          "x": 0.5,
+			          "y": 0.35
+			        }
+			      },
+			      "position": "top center",
+			      "title": "aloha fresh",
+			      "description": "we fucking love this place 10/10 i love poke i should have never quit pokehouse"
+			    },
+			    {
+			      "id": "04",
+			      "title": "mad yolks",
+			      "description": "for our santa cruz hang! u in my city now. so so good but lwk so so tax 9/10"
+			    },
+			    {
+			      "id": "05",
+			      "thumbnail": {
+			        "focus": {
+			          "x": 0.5,
+			          "y": 0.35
+			        }
+			      },
+			      "position": "top center",
+			      "title": "sizzling lunch",
+			      "description": "better than pepper lunch. server was being a little bitchy but i would be too if i was the only one working the front. 8/10"
+			    },
+			    {
+			      "id": "06",
+			      "title": "braised pork belly",
+			      "description": "omfg this is my favorite thing uve made 100/10"
+			    },
+			    {
+			      "id": "07",
+			      "title": "sushi w/ claire!",
+			      "description": "and then we played bananagrams. sushi 8/10 thanks for paying mommy"
+			    },
+			    {
+			      "id": "08",
+			      "title": "myungrang hot dog",
+			      "description": "main street tino nothing special 7/10"
+			    },
+			    {
+			      "id": "09",
+			      "title": "liangs village",
+			      "description": "my peoples food. 9/10"
+			    },
+			    {
+			      "id": "10",
+			      "title": "cabonara",
+			      "description": "insane safeway hang 9/10"
+			    },
+			    {
+			      "id": "11",
+			      "title": "heytea",
+			      "description": "this fuckass blue drink"
+			    },
+			    {
+			      "id": "12",
+			      "title": "sparcos",
+			      "description": "one of many.. 100/10"
+			    },
+			    {
+			      "id": "13",
+			      "title": "noahs bagels",
+			      "description": "this is the plaza where i used to go to all the time before school 9/10"
+			    },
+			    {
+			      "id": "14",
+			      "title": "homeroom",
+			      "description": "mac and cheese was gas. 10/10. you know its my fav comfort food. free the girl crying in the corner tho"
+			    },
+			    {
+			      "id": "15",
+			      "title": "sparcos x2",
+			      "description": "spartan tacos"
+			    },
+			    {
+			      "id": "16",
+			      "title": "sparcos x3",
+			      "description": "okay damn no way we got this b2b"
+			    },
+			    {
+			      "id": "17",
+			      "title": "aloha fresh",
+			      "description": "this is lowkey the spot poke always hits so fucking good"
+			    },
+			    {
+			      "id": "18",
+			      "title": "house of bagels",
+			      "description": "hobags ughgmmfmfm im such a fucking ho for hobags 100/10"
+			    },
+			    {
+			      "id": "19",
+			      "title": "toro sushi",
+			      "description": "carmel by the sea! we love sushi but tax 8/10"
+			    },
+			    {
+			      "id": "20",
+			      "title": "sul and beans",
+			      "description": "sweet treat -> claire dropping the most insane piece of information ever -> hti the yap"
+			    },
+			    {
+			      "id": "21",
+			      "title": "highland hand pulled noodles",
+			      "description": "so good and soooo filling 10/10. also my peoples food."
+			    },
+			    {
+			      "id": "22",
+			      "title": "bloom",
+			      "description": "even when its rich white people breakfast im getting salmon nox 10/10"
+			    },
+			    {
+			      "id": "23",
+			      "title": "happy donuts",
+			      "description": "1k cal meal 0 protein 10/10"
+			    },
+			    {
+			      "id": "24",
+			      "title": "marugame",
+			      "description": "i dont want to talk about this. 9/10"
+			    },
+			    {
+			      "id": "25",
+			      "title": "siam station!",
+			      "description": "i can't believe u didnt eat ur leftovers. 10/10"
+			    },
+			    {
+			      "id": "26",
+			      "title": "muukata 6395",
+			      "description": "for my birthday!! i love eating meat and i love you so perfect combination 1000/10"
+			    },
+			    {
+			      "id": "27",
+			      "title": "bambu",
+			      "description": "why was the store so nice. i wonder about the 4 sisters"
+			    },
+			    {
+			      "id": "28",
+			      "title": "porridge at julias",
+			      "description": "her boyfriend is so not real hes so stupid and funny. porridge was gas too i love eating free at julias 10/10"
+			    },
+			    {
+			      "id": "29",
+			      "title": "sparcos x4",
+			      "description": "spartan tacos. i was moody lol."
+			    },
+			    {
+			      "id": "30",
+			      "title": "wonton udon",
+			      "description": "i helped wrap the wontons w/ u !!! super fun and super yummy 10/10"
+			    },
+			    {
+			      "id": "31",
+			      "title": "steak dinna for vday",
+			      "description": "marry me? yes. 100/10 best valentines day ever"
+			    },
+			    {
+			      "id": "32",
+			      "title": "poke house",
+			      "description": "poke house 3 years later 9/10 but +1 point bc its basically free"
+			    },
+			    {
+			      "id": "33",
+			      "title": "hey tea",
+			      "description": "mochi yinje black milk tea ts was actually so buss 10/10 only boba i've ever wanted to get again myself"
+			    }
+			  ],
+			  "elo": {
+			    "defaultRating": 1000,
+			    "kFactor": 32,
+			    "entries": [
+			      {
+			        "id": "01",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "02",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "03",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "04",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "05",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "06",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "07",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "08",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "09",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "10",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "11",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "12",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "13",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "14",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "15",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "16",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "17",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "18",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "19",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "20",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "21",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "22",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "23",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "24",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "25",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "26",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "27",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "28",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "29",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "30",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "31",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "32",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      },
+			      {
+			        "id": "33",
+			        "rating": 1000,
+			        "wins": 0,
+			        "losses": 0
+			      }
+			    ]
+			  }
+			}
+		</script>
+		<script src="assets/js/rankings.js"></script>
 	</body>
 </html>
--- a/scripts/build.js
+++ b/scripts/build.js
@@ -2,7 +2,7 @@ const fs = require("fs");
 const path = require("path");

 const { getRankedMeals, syncEloWithMeals } = require("./lib/elo");
-const { loadMeals, repoRoot } = require("./lib/meals");
+const { loadMeals, repoRoot, validateMealAssets } = require("./lib/meals");

 const indexTemplatePath = path.join(repoRoot, "templates", "index.html");
 const indexOutputPath = path.join(repoRoot, "index.html");
@@ -24,6 +24,20 @@ function escapeHtml(value) {
    .replace(/"/g, "&quot;");
 }

+function serializeJsonForHtml(value) {
+  return JSON.stringify(value, null, 2)
+    .replace(/</g, "\\u003c")
+    .replace(/\u2028/g, "\\u2028")
+    .replace(/\u2029/g, "\\u2029");
+}
+
+function indentBlock(text, indent) {
+  return text
+    .split("\n")
+    .map((line) => `${indent}${line}`)
+    .join("\n");
+}
+
 function renderGalleryItem(meal, eol) {
  const attrs = [`class="thumbnail"`, `href="images/fulls/${meal.id}.jpg"`];

@@ -53,7 +67,7 @@ function renderRankingSummary(meals, eloData) {

  return `\t\t\t\t<p class="ranking-summary">${meals.length} ${mealLabel} seeded at Elo ${formatRating(
    eloData.defaultRating
-  )} until head-to-head voting starts.</p>`;
+  )}. Enable JavaScript to vote and reorder them.</p>`;
 }

 function renderRankingMeta(rankedMeal) {
@@ -91,6 +105,16 @@ function renderRankings(rankedMeals, eol) {
    .join(eol);
 }

+function renderRankingsSeedData(meals, eloData) {
+  return indentBlock(
+    serializeJsonForHtml({
+      meals,
+      elo: eloData,
+    }),
+    "\t\t\t"
+  );
+}
+
 function replaceBlock(template, token, replacement) {
  const pattern = new RegExp(`^[\\t ]*\\{\\{${token}\\}\\}$`, "m");

@@ -102,6 +126,7 @@ function replaceBlock(template, token, replacement) {
 }

 function buildIndex(meals = loadMeals()) {
+  validateMealAssets(meals);
  const template = fs.readFileSync(indexTemplatePath, "utf8");
  const eol = detectEol(template);

@@ -112,6 +137,7 @@ function buildRankings(
  meals = loadMeals(),
  eloData = syncEloWithMeals(meals)
 ) {
+  validateMealAssets(meals);
  const template = fs.readFileSync(rankingsTemplatePath, "utf8");
  const eol = detectEol(template);
  const rankedMeals = getRankedMeals(meals, eloData);
@@ -120,8 +146,13 @@ function buildRankings(
    "ranking_summary",
    renderRankingSummary(meals, eloData)
  );
+  const withSeedData = replaceBlock(
+    withSummary,
+    "rankings_seed_data",
+    renderRankingsSeedData(meals, eloData)
+  );

-  return replaceBlock(withSummary, "ranking_items", renderRankings(rankedMeals, eol));
+  return replaceBlock(withSeedData, "ranking_items", renderRankings(rankedMeals, eol));
 }

 function writeFile(filePath, contents) {
--- a/scripts/check.js
+++ b/scripts/check.js
@@ -0,0 +1,151 @@
+const fs = require("fs");
+const path = require("path");
+
+const { getEloAlignmentReport, loadEloData } = require("./lib/elo");
+const {
+  fullsDir,
+  loadMeals,
+  repoRoot,
+  thumbsDir,
+  validateMealAssets,
+} = require("./lib/meals");
+
+const indexPath = path.join(repoRoot, "index.html");
+const rankingsPath = path.join(repoRoot, "rankings.html");
+
+function listJpgIds(directoryPath) {
+  if (!fs.existsSync(directoryPath)) {
+    return [];
+  }
+
+  return fs
+    .readdirSync(directoryPath, { withFileTypes: true })
+    .filter(
+      (entry) => entry.isFile() && path.extname(entry.name).toLowerCase() === ".jpg"
+    )
+    .map((entry) => path.basename(entry.name, ".jpg"))
+    .sort((left, right) => left.localeCompare(right, undefined, { numeric: true }));
+}
+
+function getUnexpectedIds(directoryPath, expectedIds) {
+  return listJpgIds(directoryPath).filter((id) => !expectedIds.has(id));
+}
+
+function countMatches(text, pattern) {
+  return (text.match(pattern) || []).length;
+}
+
+function parseRankingsSeedData(rankingsHtml) {
+  const match = rankingsHtml.match(
+    /<script id="rankings-seed-data" type="application\/json">([\s\S]*?)<\/script>/
+  );
+
+  if (!match) {
+    throw new Error("Generated rankings.html is missing embedded rankings seed data");
+  }
+
+  return JSON.parse(match[1]);
+}
+
+function validateGeneratedPages(meals, eloData) {
+  if (!fs.existsSync(indexPath)) {
+    throw new Error("Generated index.html is missing; run npm run build");
+  }
+
+  if (!fs.existsSync(rankingsPath)) {
+    throw new Error("Generated rankings.html is missing; run npm run build");
+  }
+
+  const indexHtml = fs.readFileSync(indexPath, "utf8");
+  const rankingsHtml = fs.readFileSync(rankingsPath, "utf8");
+  const galleryArticleCount = countMatches(indexHtml, /<article>/g);
+  const rankingCardCount = countMatches(rankingsHtml, /class="ranking-card"/g);
+
+  if (galleryArticleCount !== meals.length) {
+    throw new Error(
+      `Generated index.html is out of sync: expected ${meals.length} gallery entries, found ${galleryArticleCount}`
+    );
+  }
+
+  if (rankingCardCount !== meals.length) {
+    throw new Error(
+      `Generated rankings.html is out of sync: expected ${meals.length} ranking cards, found ${rankingCardCount}`
+    );
+  }
+
+  if (!rankingsHtml.includes('src="assets/js/rankings.js"')) {
+    throw new Error("Generated rankings.html is missing the interactive rankings script");
+  }
+
+  const seedData = parseRankingsSeedData(rankingsHtml);
+
+  if (!Array.isArray(seedData.meals) || seedData.meals.length !== meals.length) {
+    throw new Error("Generated rankings.html has stale embedded meal seed data");
+  }
+
+  if (
+    !seedData.elo ||
+    !Array.isArray(seedData.elo.entries) ||
+    seedData.elo.entries.length !== eloData.entries.length
+  ) {
+    throw new Error("Generated rankings.html has stale embedded Elo seed data");
+  }
+}
+
+function main() {
+  const meals = loadMeals();
+  const eloData = loadEloData();
+  const expectedIds = new Set(meals.map((meal) => meal.id));
+  const alignment = getEloAlignmentReport(meals, eloData);
+
+  validateMealAssets(meals);
+
+  if (alignment.missingEntryIds.length > 0 || alignment.unexpectedEntryIds.length > 0) {
+    const messages = [];
+
+    if (alignment.missingEntryIds.length > 0) {
+      messages.push(
+        `Missing Elo entries for meal ids: ${alignment.missingEntryIds.join(", ")}`
+      );
+    }
+
+    if (alignment.unexpectedEntryIds.length > 0) {
+      messages.push(
+        `Unexpected Elo entries with no meal: ${alignment.unexpectedEntryIds.join(", ")}`
+      );
+    }
+
+    throw new Error(messages.join("\n"));
+  }
+
+  const unexpectedFulls = getUnexpectedIds(fullsDir, expectedIds);
+
+  if (unexpectedFulls.length > 0) {
+    throw new Error(
+      `Unexpected full-size image files with no meal entry: ${unexpectedFulls.join(", ")}`
+    );
+  }
+
+  const unexpectedThumbs = getUnexpectedIds(thumbsDir, expectedIds);
+
+  if (unexpectedThumbs.length > 0) {
+    throw new Error(
+      `Unexpected thumbnail files with no meal entry: ${unexpectedThumbs.join(", ")}`
+    );
+  }
+
+  validateGeneratedPages(meals, eloData);
+
+  console.log(
+    `Validation passed: ${meals.length} meals, ${eloData.entries.length} Elo entries, generated pages and image assets are in sync.`
+  );
+}
+
+if (require.main === module) {
+  try {
+    main();
+  } catch (error) {
+    console.error(error.message);
+    process.exitCode = 1;
+  }
+}
--- a/scripts/lib/elo.js
+++ b/scripts/lib/elo.js
@@ -99,6 +99,20 @@ function syncEloWithMeals(meals) {
  return syncedData;
 }

+function getEloAlignmentReport(meals, eloData) {
+  const mealIds = new Set(meals.map((meal) => meal.id));
+  const eloIds = new Set(eloData.entries.map((entry) => entry.id));
+
+  return {
+    missingEntryIds: meals
+      .map((meal) => meal.id)
+      .filter((mealId) => !eloIds.has(mealId)),
+    unexpectedEntryIds: eloData.entries
+      .map((entry) => entry.id)
+      .filter((entryId) => !mealIds.has(entryId)),
+  };
+}
+
 function compareRankedMeals(left, right) {
  if (right.rating !== left.rating) {
    return right.rating - left.rating;
@@ -132,6 +146,7 @@ function getRankedMeals(meals, eloData) {

 module.exports = {
  eloPath,
+  getEloAlignmentReport,
  getRankedMeals,
  loadEloData,
  saveEloData,
--- a/scripts/lib/meals.js
+++ b/scripts/lib/meals.js
@@ -3,6 +3,12 @@ const path = require("path");

 const repoRoot = path.resolve(__dirname, "..", "..");
 const mealsPath = path.join(repoRoot, "data", "meals.json");
+const fullsDir = path.join(repoRoot, "images", "fulls");
+const thumbsDir = path.join(repoRoot, "images", "thumbs");
+
+function isNonEmptyString(value) {
+  return typeof value === "string" && value.trim().length > 0;
+}

 function validateThumbnail(meal, index) {
  if (meal.thumbnail === undefined) {
@@ -55,7 +61,7 @@ function validateMeals(meals) {
    }

    for (const field of ["id", "title", "description"]) {
-      if (typeof meal[field] !== "string" || meal[field].length === 0) {
+      if (!isNonEmptyString(meal[field])) {
        throw new Error(`Meal ${index} is missing required string field "${field}"`);
      }
    }
@@ -64,8 +70,8 @@ function validateMeals(meals) {
      throw new Error(`Meal ${index} has a non-numeric id "${meal.id}"`);
    }

-    if (meal.position !== undefined && typeof meal.position !== "string") {
-      throw new Error(`Meal ${index} has a non-string "position" value`);
+    if (meal.position !== undefined && !isNonEmptyString(meal.position)) {
+      throw new Error(`Meal ${index} has an invalid "position" value`);
    }

    if (ids.has(meal.id)) {
@@ -91,6 +97,49 @@ function saveMeals(meals) {
  fs.writeFileSync(mealsPath, `${JSON.stringify(meals, null, 2)}\n`);
 }

+function getMealImagePaths(mealOrId) {
+  const mealId =
+    typeof mealOrId === "string" ? mealOrId : mealOrId && typeof mealOrId.id === "string" ? mealOrId.id : null;
+
+  if (!mealId) {
+    throw new Error("Expected a meal object or meal id string");
+  }
+
+  return {
+    fullPath: path.join(fullsDir, `${mealId}.jpg`),
+    thumbPath: path.join(thumbsDir, `${mealId}.jpg`),
+  };
+}
+
+function validateMealAssets(meals, options = {}) {
+  const settings = {
+    requireFull: true,
+    requireThumb: true,
+    ...options,
+  };
+  const missingAssets = [];
+
+  for (const meal of meals) {
+    const { fullPath, thumbPath } = getMealImagePaths(meal);
+
+    if (settings.requireFull && !fs.existsSync(fullPath)) {
+      missingAssets.push(
+        `Meal ${meal.id} is missing full-size image: ${path.relative(repoRoot, fullPath)}`
+      );
+    }
+
+    if (settings.requireThumb && !fs.existsSync(thumbPath)) {
+      missingAssets.push(
+        `Meal ${meal.id} is missing thumbnail image: ${path.relative(repoRoot, thumbPath)}`
+      );
+    }
+  }
+
+  if (missingAssets.length > 0) {
+    throw new Error(`Missing image assets:\n${missingAssets.join("\n")}`);
+  }
+}
+
 function getNextMealId(meals) {
  if (meals.length === 0) {
    return "01";
@@ -108,9 +157,13 @@ function getNextMealId(meals) {
 }

 module.exports = {
+  fullsDir,
  getNextMealId,
+  getMealImagePaths,
  loadMeals,
  mealsPath,
  repoRoot,
  saveMeals,
+  thumbsDir,
+  validateMealAssets,
 };
--- a/scripts/lib/rankings-state.js
+++ b/scripts/lib/rankings-state.js
@@ -0,0 +1,380 @@
+const fs = require("fs");
+const path = require("path");
+
+const { loadEloData } = require("./elo");
+const { loadMeals, repoRoot } = require("./meals");
+
+const STATE_VERSION = 1;
+const defaultStatePath = path.join(repoRoot, ".runtime", "rankings-state.json");
+
+function isValidMealId(id) {
+  return typeof id === "string" && /^\d+$/.test(id);
+}
+
+function createDefaultEntry(id, defaultRating) {
+  return {
+    id,
+    rating: defaultRating,
+    wins: 0,
+    losses: 0,
+  };
+}
+
+function cloneEntry(entry) {
+  return {
+    id: entry.id,
+    rating: entry.rating,
+    wins: entry.wins,
+    losses: entry.losses,
+  };
+}
+
+function roundRating(rating) {
+  return Math.round(rating * 1000) / 1000;
+}
+
+function expectedScore(rating, opponentRating) {
+  return 1 / (1 + Math.pow(10, (opponentRating - rating) / 400));
+}
+
+function isValidStoredEntry(entry) {
+  if (!entry || typeof entry !== "object" || Array.isArray(entry)) {
+    return false;
+  }
+
+  if (typeof entry.id !== "string" || !/^\d+$/.test(entry.id)) {
+    return false;
+  }
+
+  if (typeof entry.rating !== "number" || !Number.isFinite(entry.rating) || entry.rating <= 0) {
+    return false;
+  }
+
+  return ["wins", "losses"].every(
+    (field) => Number.isInteger(entry[field]) && entry[field] >= 0
+  );
+}
+
+function createSeedState(seedData) {
+  return {
+    version: STATE_VERSION,
+    voteCount: 0,
+    lastPairKey: null,
+    updatedAt: null,
+    undo: null,
+    elo: {
+      defaultRating: seedData.elo.defaultRating,
+      kFactor: seedData.elo.kFactor,
+      entries: seedData.meals.map((meal) => {
+        const seedEntry =
+          seedData.elo.entries.find((entry) => entry.id === meal.id) ||
+          createDefaultEntry(meal.id, seedData.elo.defaultRating);
+
+        return cloneEntry(seedEntry);
+      }),
+    },
+  };
+}
+
+function syncStateCore(seedData, storedState) {
+  if (!storedState || typeof storedState !== "object" || Array.isArray(storedState)) {
+    return createSeedState(seedData);
+  }
+
+  const storedEntries = Array.isArray(storedState.elo?.entries)
+    ? storedState.elo.entries.filter(isValidStoredEntry)
+    : [];
+  const storedEntryById = new Map(storedEntries.map((entry) => [entry.id, entry]));
+  const seedEntryById = new Map(seedData.elo.entries.map((entry) => [entry.id, entry]));
+  const entries = seedData.meals.map((meal) => {
+    const storedEntry = storedEntryById.get(meal.id);
+
+    if (storedEntry) {
+      return cloneEntry(storedEntry);
+    }
+
+    const seedEntry =
+      seedEntryById.get(meal.id) || createDefaultEntry(meal.id, seedData.elo.defaultRating);
+
+    return cloneEntry(seedEntry);
+  });
+  const derivedVoteCount = entries.reduce((sum, entry) => sum + entry.wins, 0);
+
+  return {
+    version: STATE_VERSION,
+    voteCount:
+      Number.isInteger(storedState.voteCount) && storedState.voteCount >= derivedVoteCount
+        ? storedState.voteCount
+        : derivedVoteCount,
+    lastPairKey: typeof storedState.lastPairKey === "string" ? storedState.lastPairKey : null,
+    updatedAt: typeof storedState.updatedAt === "string" ? storedState.updatedAt : null,
+    undo: null,
+    elo: {
+      defaultRating: seedData.elo.defaultRating,
+      kFactor: seedData.elo.kFactor,
+      entries,
+    },
+  };
+}
+
+function createPairKey(leftId, rightId) {
+  return [leftId, rightId].sort().join(":");
+}
+
+function createUndoSnapshot(state) {
+  return {
+    voteCount: state.voteCount,
+    lastPairKey: state.lastPairKey,
+    updatedAt: state.updatedAt,
+    elo: {
+      defaultRating: state.elo.defaultRating,
+      kFactor: state.elo.kFactor,
+      entries: state.elo.entries.map(cloneEntry),
+    },
+  };
+}
+
+function resolveUndoPairIds(winnerId, loserId, leftId, rightId) {
+  const validPair =
+    isValidMealId(leftId) &&
+    isValidMealId(rightId) &&
+    leftId !== rightId &&
+    [leftId, rightId].includes(winnerId) &&
+    [leftId, rightId].includes(loserId);
+
+  if (validPair) {
+    return { leftId, rightId };
+  }
+
+  return { leftId: winnerId, rightId: loserId };
+}
+
+function syncUndo(seedData, storedUndo) {
+  if (!storedUndo || typeof storedUndo !== "object" || Array.isArray(storedUndo)) {
+    return null;
+  }
+
+  const { leftId, rightId, winnerId, loserId, snapshot } = storedUndo;
+
+  if (
+    !isValidMealId(leftId) ||
+    !isValidMealId(rightId) ||
+    !isValidMealId(winnerId) ||
+    !isValidMealId(loserId) ||
+    leftId === rightId ||
+    winnerId === loserId
+  ) {
+    return null;
+  }
+
+  const pairIds = new Set([leftId, rightId]);
+  const mealIds = new Set(seedData.meals.map((meal) => meal.id));
+
+  if (
+    !pairIds.has(winnerId) ||
+    !pairIds.has(loserId) ||
+    ![leftId, rightId, winnerId, loserId].every((id) => mealIds.has(id))
+  ) {
+    return null;
+  }
+
+  return {
+    pairKey: createPairKey(leftId, rightId),
+    leftId,
+    rightId,
+    winnerId,
+    loserId,
+    snapshot: createUndoSnapshot(syncStateCore(seedData, snapshot)),
+  };
+}
+
+function syncStoredState(seedData, storedState) {
+  const nextState = syncStateCore(seedData, storedState);
+
+  return {
+    ...nextState,
+    undo: syncUndo(seedData, storedState?.undo),
+  };
+}
+
+function restoreUndoSnapshot(seedData, snapshot) {
+  return {
+    ...syncStateCore(seedData, snapshot),
+    undo: null,
+  };
+}
+
+function applyVote(seedData, state, vote) {
+  const { winnerId, loserId, pairKey, leftId, rightId } = vote;
+  const entryById = new Map(state.elo.entries.map((entry) => [entry.id, cloneEntry(entry)]));
+  const winner = entryById.get(winnerId);
+  const loser = entryById.get(loserId);
+  const undoPair = resolveUndoPairIds(winnerId, loserId, leftId, rightId);
+  const resolvedPairKey =
+    typeof pairKey === "string" && pairKey.length > 0
+      ? pairKey
+      : createPairKey(undoPair.leftId, undoPair.rightId);
+
+  if (!winner || !loser) {
+    throw new Error("Vote referenced an unknown meal id");
+  }
+
+  const winnerExpected = expectedScore(winner.rating, loser.rating);
+  const loserExpected = expectedScore(loser.rating, winner.rating);
+
+  winner.rating = roundRating(winner.rating + state.elo.kFactor * (1 - winnerExpected));
+  loser.rating = roundRating(loser.rating + state.elo.kFactor * (0 - loserExpected));
+  winner.wins += 1;
+  loser.losses += 1;
+
+  return {
+    ...state,
+    voteCount: state.voteCount + 1,
+    lastPairKey: resolvedPairKey,
+    updatedAt: new Date().toISOString(),
+    undo: {
+      pairKey: createPairKey(undoPair.leftId, undoPair.rightId),
+      leftId: undoPair.leftId,
+      rightId: undoPair.rightId,
+      winnerId,
+      loserId,
+      snapshot: createUndoSnapshot(state),
+    },
+    elo: {
+      ...state.elo,
+      entries: seedData.meals.map((meal) => entryById.get(meal.id)),
+    },
+  };
+}
+
+function undoVote(seedData, state) {
+  if (!state.undo) {
+    return state;
+  }
+
+  return restoreUndoSnapshot(seedData, state.undo.snapshot);
+}
+
+function resolveStatePath(statePath) {
+  return statePath ? path.resolve(statePath) : defaultStatePath;
+}
+
+function loadSeedData() {
+  return {
+    meals: loadMeals(),
+    elo: loadEloData(),
+  };
+}
+
+function readPersistedState(statePath) {
+  if (!fs.existsSync(statePath)) {
+    return null;
+  }
+
+  return JSON.parse(fs.readFileSync(statePath, "utf8"));
+}
+
+function writePersistedState(statePath, state) {
+  fs.mkdirSync(path.dirname(statePath), { recursive: true });
+
+  const nextState = `${JSON.stringify(state, null, 2)}\n`;
+  const tempPath = `${statePath}.tmp`;
+
+  fs.writeFileSync(tempPath, nextState);
+  fs.renameSync(tempPath, statePath);
+}
+
+function loadRankingsState(options = {}) {
+  const statePath = resolveStatePath(options.statePath);
+  const seedData = loadSeedData();
+  const storedState = readPersistedState(statePath);
+
+  return syncStoredState(seedData, storedState);
+}
+
+function saveRankingsState(state, options = {}) {
+  const statePath = resolveStatePath(options.statePath);
+  const seedData = loadSeedData();
+  const nextState = syncStoredState(seedData, state);
+
+  writePersistedState(statePath, nextState);
+
+  return nextState;
+}
+
+function recordVote(vote, options = {}) {
+  if (!vote || typeof vote !== "object" || Array.isArray(vote)) {
+    throw new Error("Vote payload must be an object");
+  }
+
+  const { winnerId, loserId, pairKey, leftId, rightId } = vote;
+
+  if (!isValidMealId(winnerId)) {
+    throw new Error("Vote payload is missing a valid winnerId");
+  }
+
+  if (!isValidMealId(loserId)) {
+    throw new Error("Vote payload is missing a valid loserId");
+  }
+
+  if (winnerId === loserId) {
+    throw new Error("winnerId and loserId must be different");
+  }
+
+  if (leftId !== undefined || rightId !== undefined) {
+    if (!isValidMealId(leftId) || !isValidMealId(rightId) || leftId === rightId) {
+      throw new Error("Vote payload is missing a valid left/right pair");
+    }
+
+    if (![leftId, rightId].includes(winnerId) || ![leftId, rightId].includes(loserId)) {
+      throw new Error("Vote payload leftId/rightId must match winnerId/loserId");
+    }
+  }
+
+  const statePath = resolveStatePath(options.statePath);
+  const seedData = loadSeedData();
+  const storedState = syncStoredState(seedData, readPersistedState(statePath));
+  const nextState = applyVote(seedData, storedState, {
+    winnerId,
+    loserId,
+    pairKey,
+    leftId,
+    rightId,
+  });
+
+  writePersistedState(statePath, nextState);
+
+  return nextState;
+}
+
+function undoLastRankingsVote(options = {}) {
+  const statePath = resolveStatePath(options.statePath);
+  const seedData = loadSeedData();
+  const storedState = syncStoredState(seedData, readPersistedState(statePath));
+  const nextState = undoVote(seedData, storedState);
+
+  writePersistedState(statePath, nextState);
+
+  return nextState;
+}
+
+function resetRankingsState(options = {}) {
+  const statePath = resolveStatePath(options.statePath);
+  const seedData = loadSeedData();
+  const nextState = createSeedState(seedData);
+
+  writePersistedState(statePath, nextState);
+
+  return nextState;
+}
+
+module.exports = {
+  createSeedState,
+  defaultStatePath,
+  loadRankingsState,
+  recordVote,
+  resetRankingsState,
+  saveRankingsState,
+  syncStoredState,
+  undoLastRankingsVote,
+};
--- a/scripts/serve.js
+++ b/scripts/serve.js
@@ -0,0 +1,302 @@
+const fs = require("fs");
+const http = require("http");
+const path = require("path");
+
+const { repoRoot } = require("./lib/meals");
+const {
+  defaultStatePath,
+  loadRankingsState,
+  recordVote,
+  resetRankingsState,
+  undoLastRankingsVote,
+} = require("./lib/rankings-state");
+
+const DEFAULT_HOST = "127.0.0.1";
+const DEFAULT_PORT = 4321;
+const MAX_REQUEST_BODY_BYTES = 16 * 1024;
+const MIME_TYPES = {
+  ".css": "text/css; charset=utf-8",
+  ".gif": "image/gif",
+  ".html": "text/html; charset=utf-8",
+  ".ico": "image/x-icon",
+  ".jpg": "image/jpeg",
+  ".js": "application/javascript; charset=utf-8",
+  ".json": "application/json; charset=utf-8",
+  ".map": "application/json; charset=utf-8",
+  ".mp3": "audio/mpeg",
+  ".png": "image/png",
+  ".svg": "image/svg+xml",
+  ".ttf": "font/ttf",
+  ".txt": "text/plain; charset=utf-8",
+  ".webmanifest": "application/manifest+json; charset=utf-8",
+  ".woff": "font/woff",
+  ".woff2": "font/woff2",
+};
+
+function parseArgs(argv) {
+  const options = {
+    host: process.env.HOST || DEFAULT_HOST,
+    port: Number.parseInt(process.env.PORT || String(DEFAULT_PORT), 10),
+    rankingsStatePath: path.resolve(process.env.RANKINGS_STATE_PATH || defaultStatePath),
+  };
+
+  for (let index = 0; index < argv.length; index += 1) {
+    const arg = argv[index];
+    const value = argv[index + 1];
+
+    if (arg === "--host" && value) {
+      options.host = value;
+      index += 1;
+      continue;
+    }
+
+    if (arg === "--port" && value) {
+      options.port = Number.parseInt(value, 10);
+      index += 1;
+      continue;
+    }
+
+    if (arg === "--rankings-state-path" && value) {
+      options.rankingsStatePath = path.resolve(value);
+      index += 1;
+    }
+  }
+
+  if (!Number.isInteger(options.port) || options.port <= 0 || options.port > 65535) {
+    throw new Error("Port must be an integer between 1 and 65535");
+  }
+
+  return options;
+}
+
+function getContentType(filePath) {
+  return MIME_TYPES[path.extname(filePath).toLowerCase()] || "application/octet-stream";
+}
+
+function hasHiddenSegment(pathname) {
+  return pathname.split("/").some((segment) => segment.startsWith(".") && segment.length > 1);
+}
+
+function resolveRequestPath(pathname) {
+  if (hasHiddenSegment(pathname)) {
+    return null;
+  }
+
+  const requestedPath = pathname === "/" ? "/index.html" : pathname;
+  const absolutePath = path.resolve(repoRoot, `.${requestedPath}`);
+  const withinRepo =
+    absolutePath === repoRoot || absolutePath.startsWith(`${repoRoot}${path.sep}`);
+
+  if (!withinRepo) {
+    return null;
+  }
+
+  if (fs.existsSync(absolutePath) && fs.statSync(absolutePath).isDirectory()) {
+    return path.join(absolutePath, "index.html");
+  }
+
+  if (
+    path.extname(absolutePath) === "" &&
+    !fs.existsSync(absolutePath) &&
+    fs.existsSync(`${absolutePath}.html`) &&
+    fs.statSync(`${absolutePath}.html`).isFile()
+  ) {
+    return `${absolutePath}.html`;
+  }
+
+  return absolutePath;
+}
+
+function sendJson(response, statusCode, payload) {
+  response.writeHead(statusCode, {
+    "Cache-Control": "no-store",
+    "Content-Type": "application/json; charset=utf-8",
+  });
+  response.end(`${JSON.stringify(payload, null, 2)}\n`);
+}
+
+function sendText(response, statusCode, body) {
+  response.writeHead(statusCode, {
+    "Cache-Control": "no-store",
+    "Content-Type": "text/plain; charset=utf-8",
+  });
+  response.end(body);
+}
+
+function sendRedirect(response, location) {
+  response.writeHead(301, {
+    Location: location,
+    "Cache-Control": "no-store",
+  });
+  response.end();
+}
+
+function parseJsonBody(request) {
+  return new Promise((resolve, reject) => {
+    const chunks = [];
+    let totalBytes = 0;
+
+    request.on("data", (chunk) => {
+      totalBytes += chunk.length;
+
+      if (totalBytes > MAX_REQUEST_BODY_BYTES) {
+        reject(new Error("Request body is too large"));
+        request.destroy();
+        return;
+      }
+
+      chunks.push(chunk);
+    });
+
+    request.on("end", () => {
+      if (chunks.length === 0) {
+        resolve({});
+        return;
+      }
+
+      try {
+        resolve(JSON.parse(Buffer.concat(chunks).toString("utf8")));
+      } catch (error) {
+        reject(new Error("Request body must be valid JSON"));
+      }
+    });
+
+    request.on("error", reject);
+  });
+}
+
+function sendFile(response, filePath) {
+  const stream = fs.createReadStream(filePath);
+
+  response.writeHead(200, {
+    "Content-Type": getContentType(filePath),
+    "Cache-Control": "no-cache",
+  });
+
+  stream.pipe(response);
+  stream.on("error", () => {
+    sendText(response, 500, "Failed to read file");
+  });
+}
+
+async function handleApiRequest(request, response, pathname, options) {
+  if (pathname === "/api/rankings" && request.method === "GET") {
+    sendJson(response, 200, loadRankingsState({ statePath: options.rankingsStatePath }));
+    return true;
+  }
+
+  if (pathname === "/api/rankings/vote" && request.method === "POST") {
+    const body = await parseJsonBody(request);
+    sendJson(response, 200, recordVote(body, { statePath: options.rankingsStatePath }));
+    return true;
+  }
+
+  if (pathname === "/api/rankings/reset" && request.method === "POST") {
+    sendJson(response, 200, resetRankingsState({ statePath: options.rankingsStatePath }));
+    return true;
+  }
+
+  if (pathname === "/api/rankings/undo" && request.method === "POST") {
+    sendJson(response, 200, undoLastRankingsVote({ statePath: options.rankingsStatePath }));
+    return true;
+  }
+
+  if (
+    pathname === "/api/rankings" ||
+    pathname === "/api/rankings/vote" ||
+    pathname === "/api/rankings/reset" ||
+    pathname === "/api/rankings/undo"
+  ) {
+    sendText(response, 405, "Method not allowed");
+    return true;
+  }
+
+  if (pathname.startsWith("/api/")) {
+    sendText(response, 404, "Not found");
+    return true;
+  }
+
+  return false;
+}
+
+function createServer(options) {
+  return http.createServer(async (request, response) => {
+    let pathname;
+    let search;
+
+    try {
+      const requestUrl = new URL(request.url || "/", "http://localhost");
+      pathname = decodeURIComponent(requestUrl.pathname);
+      search = requestUrl.search;
+    } catch (error) {
+      sendText(response, 400, "Bad request");
+      return;
+    }
+
+    if (request.method === "GET" || request.method === "HEAD") {
+      if (pathname === "/index.html") {
+        sendRedirect(response, `/${search}`);
+        return;
+      }
+
+      if (pathname.endsWith(".html") && pathname !== "/index.html") {
+        sendRedirect(response, `${pathname.slice(0, -5)}${search}`);
+        return;
+      }
+    }
+
+    try {
+      if (await handleApiRequest(request, response, pathname, options)) {
+        return;
+      }
+    } catch (error) {
+      const statusCode =
+        error.message === "Request body must be valid JSON" ||
+        error.message === "Request body is too large" ||
+        error.message.startsWith("Vote payload") ||
+        error.message === "winnerId and loserId must be different"
+          ? 400
+          : 500;
+
+      if (statusCode >= 500) {
+        console.error(error);
+      }
+
+      sendJson(response, statusCode, { error: error.message });
+      return;
+    }
+
+    const filePath = resolveRequestPath(pathname);
+
+    if (!filePath) {
+      sendText(response, 403, "Forbidden");
+      return;
+    }
+
+    if (!fs.existsSync(filePath) || !fs.statSync(filePath).isFile()) {
+      sendText(response, 404, "Not found");
+      return;
+    }
+
+    sendFile(response, filePath);
+  });
+}
+
+function main() {
+  const options = parseArgs(process.argv.slice(2));
+  const server = createServer(options);
+
+  server.listen(options.port, options.host, () => {
+    console.log(`Serving ${repoRoot} at http://${options.host}:${options.port}`);
+    console.log(`Rankings state path: ${options.rankingsStatePath}`);
+  });
+}
+
+if (require.main === module) {
+  try {
+    main();
+  } catch (error) {
+    console.error(error.message);
+    process.exitCode = 1;
+  }
+}
--- a/templates/index.html
+++ b/templates/index.html
@@ -30,9 +30,9 @@
 				<h1>for vham :3</h1>
 				<p id="haiku">Please enable javascript >.<</p>
 				<p class="page-links">
-					<a href="index.html" aria-current="page">gallery</a>
+					<a href="./" aria-current="page">gallery</a>
 					<span class="page-links__separator">/</span>
-					<a href="rankings.html">rankings</a>
+					<a href="rankings">rankings</a>
 				</p>
 			</header>

--- a/templates/rankings.html
+++ b/templates/rankings.html
@@ -28,14 +28,35 @@
 			<header id="header">
 				<img src="images/meow.gif" alt="meow" id="gifone">
 				<h1>food power rankings</h1>
-				<p>static Elo seeds for every meal before the head-to-head voting page exists.</p>
+				<p>pick the better meal, one pair at a time, and the board updates live in this browser.</p>
 				<p class="page-links">
-					<a href="index.html">gallery</a>
+					<a href="./">gallery</a>
 					<span class="page-links__separator">/</span>
-					<a href="rankings.html" aria-current="page">rankings</a>
+					<a href="rankings" aria-current="page">rankings</a>
 				</p>
 			</header>

+			<!-- Voting -->
+			<section id="voting">
+				<div class="voting-panel">
+					<div class="voting-panel__intro">
+						<p class="voting-panel__eyebrow">Head-To-Head Voting</p>
+						<h2>Pick the winner.</h2>
+						<p class="vote-status" id="vote-status" aria-live="polite">Enable JavaScript to load saved rankings.</p>
+					</div>
+					<div class="voting-panel__actions">
+						<button class="button small" id="skip-pair" type="button">skip pair</button>
+						<button class="button small" id="undo-vote" type="button">go back</button>
+						<button class="button small" id="reset-rankings" type="button">reset saved rankings</button>
+					</div>
+					<p class="vote-message" id="vote-message" aria-live="polite">Enable JavaScript to load head-to-head voting.</p>
+					<div class="duel-grid" id="duel-cards">
+						<p class="duel-placeholder">Enable JavaScript to compare meals here.</p>
+					</div>
+					<p class="vote-hint">Tip: use the left and right arrow keys to vote faster, or press Z to go back.</p>
+				</div>
+			</section>
+
 			<!-- Rankings Summary -->
 			<section id="rankings-summary">
 				{{ranking_summary}}
@@ -55,5 +76,9 @@
 			</footer>

 		</div>
+		<script id="rankings-seed-data" type="application/json">
+{{rankings_seed_data}}
+		</script>
+		<script src="assets/js/rankings.js"></script>
 	</body>
 </html>
Author	SHA1	Message	Date
Ryan Chou	ac52daa454	add: go back button in rankings All checks were successful Deploy on push / deploy (push) Has been skipped Details	2026-03-23 03:05:44 -07:00
Ryan Chou	dc1dce1120	add: docker compose code All checks were successful Deploy on push / deploy (push) Has been skipped Details	2026-03-23 02:50:30 -07:00
Ryan Chou	b1403da70d	add: dockerfile and docker ignore rules All checks were successful Deploy on push / deploy (push) Has been skipped Details	2026-03-23 02:46:53 -07:00
Ryan Chou	a72e4d21d5	change: removed .html in url All checks were successful Deploy on push / deploy (push) Has been skipped Details	2026-03-23 02:40:49 -07:00
Ryan Chou	9f60ab3cca	add: persistant storage of elo ranking All checks were successful Deploy on push / deploy (push) Has been skipped Details	2026-03-22 21:18:49 -07:00
Ryan Chou	614a3d1eff	refactor: clean up gallery tooling and document the workflow All checks were successful Deploy on push / deploy (push) Has been skipped Details	2026-03-22 20:33:29 -07:00
Ryan Chou	b3a8368bab	add: pairwise elo voting workflow	2026-03-22 20:25:41 -07:00