Add level selection menu and persistence

Introduce a level selection UI and persistence for unlocked levels. Adds CSS styles and HTML markup for a floating level menu, and JS to load/save highest unlocked level to localStorage (key: mirror-game-highest-unlocked-level). Implements functions to render/toggle the menu, unlock levels on finish, and navigate to arbitrary levels via goToLevel. nextLevel now delegates to goToLevel, and setup calls loadUnlockedLevels() and setupLevelMenu() so the menu reflects progress immediately.

web/assets/css/game.css

@@ -20,6 +20,71 @@ body {
     user-select: none;
 }
 
+.level-menu-shell {
+    position: fixed;
+    top: 24px;
+    right: 24px;
+    z-index: 1100;
+    display: flex;
+    align-items: flex-start;
+    gap: 10px;
+}
+
+.level-menu-toggle {
+    border: none;
+    border-radius: 999px;
+    background: #223;
+    color: #fff;
+    padding: 12px 18px;
+    font-size: 0.95rem;
+    font-weight: 700;
+    cursor: pointer;
+    box-shadow: 0 8px 20px rgba(34, 51, 68, 0.18);
+}
+
+.level-menu-panel {
+    min-width: 180px;
+    background: rgba(255, 255, 255, 0.96);
+    border-radius: 18px;
+    padding: 14px;
+    box-shadow: 0 18px 40px rgba(34, 51, 68, 0.18);
+    border: 1px solid rgba(34, 51, 68, 0.08);
+}
+
+.level-menu-panel h2 {
+    font-size: 0.95rem;
+    color: #223;
+    margin-bottom: 10px;
+}
+
+.level-menu-list {
+    display: flex;
+    flex-direction: column;
+    gap: 8px;
+}
+
+.level-menu-item {
+    border: none;
+    border-radius: 10px;
+    padding: 10px 12px;
+    text-align: left;
+    background: #dfe5f8;
+    color: #223;
+    font-weight: 700;
+    cursor: pointer;
+}
+
+.level-menu-item.is-current {
+    background: #223;
+    color: #fff;
+}
+
+.level-menu-item:disabled {
+    background: #eceff7;
+    color: #8a92a3;
+    cursor: not-allowed;
+}
+
 main {
     display: flex;
     flex-direction: column;

web/assets/js/game.js

@@ -162,6 +162,8 @@ let rotatorIntervals = {};
 let toggledDoors = {};
 let poweredCaptors = {};
 let draggedGlassColor = null;
+let highestUnlockedLevelIndex = 0;
+const unlockedLevelsStorageKey = "mirror-game-highest-unlocked-level";
 
 function getCurrentLevel() {
     return levels[currentLevelIndex];
@@ -171,6 +173,107 @@ function getCurrentLevelConfig(configByLevel) {
     return configByLevel[currentLevelIndex] || {};
 }
 
+function loadUnlockedLevels() {
+    const savedValue = window.localStorage.getItem(unlockedLevelsStorageKey);
+    const parsedValue = Number.parseInt(savedValue || "0", 10);
+
+    if (Number.isNaN(parsedValue)) {
+        highestUnlockedLevelIndex = 0;
+        return;
+    }
+
+    highestUnlockedLevelIndex = Math.max(0, Math.min(parsedValue, levels.length - 1));
+}
+
+function saveUnlockedLevels() {
+    window.localStorage.setItem(unlockedLevelsStorageKey, String(highestUnlockedLevelIndex));
+}
+
+function unlockLevel(levelIndex) {
+    if (levelIndex <= highestUnlockedLevelIndex || levelIndex >= levels.length) {
+        return;
+    }
+
+    highestUnlockedLevelIndex = levelIndex;
+    saveUnlockedLevels();
+    renderLevelMenu();
+}
+
+function toggleLevelMenu() {
+    const levelMenuPanel = document.getElementById("level-menu-panel");
+    const levelMenuToggle = document.getElementById("level-menu-toggle");
+
+    if (!levelMenuPanel || !levelMenuToggle) {
+        return;
+    }
+
+    const isOpening = levelMenuPanel.hasAttribute("hidden");
+
+    if (isOpening) {
+        levelMenuPanel.removeAttribute("hidden");
+    } else {
+        levelMenuPanel.setAttribute("hidden", "");
+    }
+
+    levelMenuToggle.setAttribute("aria-expanded", String(isOpening));
+}
+
+function renderLevelMenu() {
+    const levelMenuList = document.getElementById("level-menu-list");
+
+    if (!levelMenuList) {
+        return;
+    }
+
+    levelMenuList.innerHTML = "";
+
+    for (let levelIndex = 0; levelIndex < levels.length; levelIndex++) {
+        const levelButton = document.createElement("button");
+        const isUnlocked = levelIndex <= highestUnlockedLevelIndex;
+        const isCurrentLevel = levelIndex === currentLevelIndex;
+
+        levelButton.type = "button";
+        levelButton.classList.add("level-menu-item");
+        levelButton.textContent = isUnlocked ? `Level ${levelIndex + 1}` : `Level ${levelIndex + 1} - Locked`;
+        levelButton.disabled = !isUnlocked;
+
+        if (isCurrentLevel) {
+            levelButton.classList.add("is-current");
+        }
+
+        levelButton.addEventListener("click", () => {
+            if (!isUnlocked) {
+                return;
+            }
+
+            goToLevel(levelIndex);
+            const levelMenuPanel = document.getElementById("level-menu-panel");
+            const levelMenuToggle = document.getElementById("level-menu-toggle");
+
+            if (levelMenuPanel) {
+                levelMenuPanel.setAttribute("hidden", "");
+            }
+
+            if (levelMenuToggle) {
+                levelMenuToggle.setAttribute("aria-expanded", "false");
+            }
+        });
+
+        levelMenuList.appendChild(levelButton);
+    }
+}
+
+function setupLevelMenu() {
+    const levelMenuToggle = document.getElementById("level-menu-toggle");
+
+    if (!levelMenuToggle) {
+        return;
+    }
+
+    levelMenuToggle.addEventListener("click", toggleLevelMenu);
+    renderLevelMenu();
+}
+
 function getCurrentGlassOptions() {
     return glassOptions[currentLevelIndex] || [];
 }
@@ -892,22 +995,19 @@ function traceLaser() {
 }
 
 function finish() {
+    unlockLevel(currentLevelIndex + 1);
+
     setTimeout(() => {
         const winOverlay = document.querySelector(".win-overlay");
         winOverlay.style.visibility = "visible";
     }, 100);
 }
 
-function nextLevel() {
-    currentLevelIndex++;
-
+function goToLevel(levelIndex) {
+    currentLevelIndex = levelIndex;
     isLevelFinished = false;
     stopAllRotatorButtons();
 
-    if (currentLevelIndex >= levels.length) {
-        currentLevelIndex = 0;
-    }
-
     initializeMirrorOrientations();
     glassPlacements = {};
     resetGlassInventory();
@@ -923,10 +1023,18 @@ function nextLevel() {
 
     const winOverlay = document.querySelector(".win-overlay");
     winOverlay.style.visibility = "hidden";
+    renderLevelMenu();
 }
 
+function nextLevel() {
+    const nextLevelIndex = currentLevelIndex + 1 >= levels.length ? 0 : currentLevelIndex + 1;
+    goToLevel(nextLevelIndex);
+}
+
+loadUnlockedLevels();
 resetGlassInventory();
 createPalette();
 initializeMirrorOrientations();
 blockBrowserDrop();
+setupLevelMenu();
 traceLaser();

web/templates/view/game.html

@@ -15,6 +15,16 @@
       <button class="win-button" onclick="nextLevel()">Next Level</button>
     </div>
 
+    <aside class="level-menu-shell">
+        <button id="level-menu-toggle" class="level-menu-toggle" type="button" aria-expanded="false" aria-controls="level-menu-panel">
+            Levels
+        </button>
+        <div id="level-menu-panel" class="level-menu-panel" hidden>
+            <h2>Choose Level</h2>
+            <div id="level-menu-list" class="level-menu-list"></div>
+        </div>
+    </aside>
+
     <script>
         atOptions = {
           'key' : '72b6ba1a1c26b9671167b66063c7e699',