feat: add first-time player tutorial walkthrough

Part of #57 — Task 4: Tutorial & Onboarding

- 5 click-through screens introducing game concepts (code, buildings,
  research, phases, keyboard shortcuts)
- Skip button on every screen, keyboard support (Enter/Escape/arrows)
- Stores completion in localStorage — only shows once for new players
- Matches existing visual style (dark theme, accent colors, monospace)
- Start Playing button on final screen with shortcut hint (? overlay)

index.html

@@ -229,6 +229,7 @@ The light is on. The room is empty."
     <script src="js/strategy.js"></script>
     <script src="js/engine.js"></script>
     <script src="js/render.js"></script>
+    <script src="js/tutorial.js"></script>
     <script src="js/main.js"></script>
   
 

js/main.js

@@ -19,8 +19,10 @@ function initGame() {
 }
 
 window.addEventListener('load', function () {
-    if (!loadGame()) {
+    const isNewGame = !loadGame();
+    if (isNewGame) {
         initGame();
+        startTutorial();
     } else {
         render();
         renderPhase();

js/tutorial.js

@@ -0,0 +1,248 @@
+// ============================================================
+// THE BEACON - Tutorial / Onboarding
+// First-time player walkthrough (4 screens + skip option)
+// ============================================================
+
+const TUTORIAL_KEY = 'the-beacon-tutorial-done';
+
+const TUTORIAL_STEPS = [
+    {
+        title: 'THE BEACON',
+        body: 'Build an AI from scratch.\n\nWrite code. Train models. Deploy to the world.\nSave lives.',
+        icon: '🏠',
+        tip: 'A sovereign AI idle game'
+    },
+    {
+        title: 'WRITE CODE',
+        body: 'Click WRITE CODE or press SPACE to generate code.\n\nClick fast for combo bonuses:\n  10× combo → bonus ops\n  20× combo → bonus knowledge\n  30×+ combo → bonus code',
+        icon: '⌨️',
+        tip: 'This is your primary action'
+    },
+    {
+        title: 'BUILD & RESEARCH',
+        body: 'Buy Buildings for passive production.\nThey generate resources automatically.\n\nResearch Projects appear as you progress.\nThey unlock powerful multipliers and new systems.',
+        icon: '🏗️',
+        tip: 'Automation is the goal'
+    },
+    {
+        title: 'PHASES & PROGRESS',
+        body: 'The game has 6 phases, from "The First Line" to "The Beacon."\n\nEach phase unlocks new buildings, projects, and challenges.\n\nYour AI grows from a script... to something that matters.',
+        icon: '📊',
+        tip: 'Watch the progress bar at the top'
+    },
+    {
+        title: 'YOU\'RE READY',
+        body: 'Buildings produce while you think.\nProjects multiply your output.\nKeep harmony high. Avoid the Drift.\n\nThe Beacon is waiting. Start writing.',
+        icon: '✦',
+        tip: 'Press ? anytime for keyboard shortcuts'
+    }
+];
+
+function isTutorialDone() {
+    try {
+        return localStorage.getItem(TUTORIAL_KEY) === 'done';
+    } catch (e) {
+        return true; // If localStorage is broken, skip tutorial
+    }
+}
+
+function markTutorialDone() {
+    try {
+        localStorage.setItem(TUTORIAL_KEY, 'done');
+    } catch (e) {
+        // silent fail
+    }
+}
+
+function createTutorialStyles() {
+    if (document.getElementById('tutorial-styles')) return;
+    const style = document.createElement('style');
+    style.id = 'tutorial-styles';
+    style.textContent = `
+#tutorial-overlay {
+    position: fixed;
+    top: 0; left: 0; right: 0; bottom: 0;
+    background: rgba(8, 8, 16, 0.96);
+    z-index: 300;
+    display: flex;
+    justify-content: center;
+    align-items: center;
+    animation: tutorial-fade-in 0.4s ease-out;
+}
+@keyframes tutorial-fade-in {
+    from { opacity: 0 } to { opacity: 1 }
+}
+#tutorial-card {
+    background: #0e0e1a;
+    border: 1px solid #1a3a5a;
+    border-radius: 10px;
+    padding: 32px 36px;
+    max-width: 420px;
+    width: 90%;
+    text-align: center;
+    animation: tutorial-slide-up 0.5s ease-out;
+    position: relative;
+}
+@keyframes tutorial-slide-up {
+    from { transform: translateY(20px); opacity: 0 }
+    to { transform: translateY(0); opacity: 1 }
+}
+#tutorial-card .t-icon {
+    font-size: 36px;
+    margin-bottom: 12px;
+    display: block;
+}
+#tutorial-card .t-title {
+    color: #4a9eff;
+    font-size: 16px;
+    font-weight: 700;
+    letter-spacing: 3px;
+    margin-bottom: 12px;
+    font-family: inherit;
+}
+#tutorial-card .t-body {
+    color: #999;
+    font-size: 11px;
+    line-height: 1.9;
+    margin-bottom: 20px;
+    white-space: pre-line;
+    font-family: inherit;
+    text-align: left;
+}
+#tutorial-card .t-tip {
+    color: #555;
+    font-size: 9px;
+    font-style: italic;
+    margin-bottom: 20px;
+    letter-spacing: 1px;
+    font-family: inherit;
+}
+#tutorial-dots {
+    display: flex;
+    gap: 6px;
+    justify-content: center;
+    margin-bottom: 18px;
+}
+#tutorial-dots .t-dot {
+    width: 6px;
+    height: 6px;
+    border-radius: 50%;
+    background: #1a1a2e;
+    transition: background 0.3s;
+}
+#tutorial-dots .t-dot.active {
+    background: #4a9eff;
+    box-shadow: 0 0 6px rgba(74, 158, 255, 0.4);
+}
+#tutorial-btns {
+    display: flex;
+    gap: 8px;
+    justify-content: center;
+}
+#tutorial-btns button {
+    font-family: inherit;
+    font-size: 11px;
+    padding: 8px 20px;
+    border-radius: 4px;
+    cursor: pointer;
+    transition: all 0.15s;
+}
+#tutorial-next-btn {
+    background: #1a2a3a;
+    border: 1px solid #4a9eff;
+    color: #4a9eff;
+}
+#tutorial-next-btn:hover {
+    background: #203040;
+    box-shadow: 0 0 12px rgba(74, 158, 255, 0.2);
+}
+#tutorial-skip-btn {
+    background: transparent;
+    border: 1px solid #333;
+    color: #555;
+}
+#tutorial-skip-btn:hover {
+    border-color: #555;
+    color: #888;
+}
+    `;
+    document.head.appendChild(style);
+}
+
+function renderTutorialStep(index) {
+    const step = TUTORIAL_STEPS[index];
+    if (!step) return;
+
+    let overlay = document.getElementById('tutorial-overlay');
+    if (!overlay) {
+        overlay = document.createElement('div');
+        overlay.id = 'tutorial-overlay';
+        document.body.appendChild(overlay);
+    }
+
+    const isLast = index === TUTORIAL_STEPS.length - 1;
+
+    // Build dots
+    let dots = '';
+    for (let i = 0; i < TUTORIAL_STEPS.length; i++) {
+        dots += `<div class="t-dot${i === index ? ' active' : ''}"></div>`;
+    }
+
+    overlay.innerHTML = `
+        <div id="tutorial-card">
+            <span class="t-icon">${step.icon}</span>
+            <div class="t-title">${step.title}</div>
+            <div class="t-body">${step.body}</div>
+            <div class="t-tip">${step.tip}</div>
+            <div id="tutorial-dots">${dots}</div>
+            <div id="tutorial-btns">
+                <button id="tutorial-skip-btn" onclick="closeTutorial()">Skip</button>
+                <button id="tutorial-next-btn" onclick="${isLast ? 'closeTutorial()' : 'nextTutorialStep()'}">${isLast ? 'Start Playing' : 'Next →'}</button>
+            </div>
+        </div>
+    `;
+
+    // Focus the next button so Enter works
+    const nextBtn = document.getElementById('tutorial-next-btn');
+    if (nextBtn) nextBtn.focus();
+}
+
+let _tutorialStep = 0;
+
+function nextTutorialStep() {
+    _tutorialStep++;
+    renderTutorialStep(_tutorialStep);
+}
+
+// Keyboard support: Enter/Right to advance, Escape to close
+document.addEventListener('keydown', function tutorialKeyHandler(e) {
+    if (!document.getElementById('tutorial-overlay')) return;
+    if (e.key === 'Enter' || e.key === 'ArrowRight') {
+        e.preventDefault();
+        if (_tutorialStep >= TUTORIAL_STEPS.length - 1) {
+            closeTutorial();
+        } else {
+            nextTutorialStep();
+        }
+    } else if (e.key === 'Escape') {
+        e.preventDefault();
+        closeTutorial();
+    }
+});
+
+function closeTutorial() {
+    const overlay = document.getElementById('tutorial-overlay');
+    if (overlay) {
+        overlay.style.animation = 'tutorial-fade-in 0.3s ease-in reverse';
+        setTimeout(() => overlay.remove(), 280);
+    }
+    markTutorialDone();
+}
+
+function startTutorial() {
+    if (isTutorialDone()) return;
+    createTutorialStyles();
+    _tutorialStep = 0;
+    // Small delay so the page renders first
+    setTimeout(() => renderTutorialStep(0), 300);
+}