fix: clamp negative resources + add tutorial focus trap

- Clamp ops, trust, compute to >= 0 in tick() to prevent negative
  values from Fenrir drain and debuff effects
- Add keyboard focus trap to tutorial overlay for accessibility
  (prevents Tab from escaping the dialog)
- Clean up focus trap handler on tutorial close

GENOME.md

@@ -8,24 +8,32 @@ The Beacon is a browser-based idle/incremental game inspired by Universal Paperc
 
 Static HTML/JS — no build step, no dependencies, no framework. Open `index.html` in any browser.
 
-**5,128 lines of JavaScript** across 10 files. **1 HTML file** with embedded CSS (~300 lines). **1 Python test file** for reckoning projects.
+**6,033 lines of JavaScript** across 11 files. **1 HTML file** with embedded CSS (~300 lines). **3 test files** (2 Node.js, 1 Python).
 
 ## Architecture
 
 ```
-index.html (UI + embedded CSS)
+index.html (UI + embedded CSS + inline JS ~5000L)
     |
     +-- js/engine.js      (1590L) Core game loop, tick, resources, buildings, projects, events
     +-- js/data.js        (944L)  Building definitions, project trees, event tables, phase data
     +-- js/render.js      (390L)  DOM rendering, UI updates, resource displays
-    +-- js/combat.js      (359L)  Boss encounters, combat mechanics
+    +-- js/combat.js      (359L)  Canvas boid-flocking combat visualization
     +-- js/sound.js       (401L)  Web Audio API ambient drone, phase-aware sound
     +-- js/dismantle.js   (570L)  The Dismantle sequence (late-game narrative)
     +-- js/main.js        (223L)  Initialization, game loop start, auto-save, help overlay
     +-- js/utils.js       (314L)  Formatting, save/load, export/import, DOM helpers
     +-- js/tutorial.js    (251L)  New player tutorial, step-by-step guidance
     +-- js/strategy.js    (68L)   NPC strategy logic for combat
-    +-- game/npc-logic.js (18L)   NPC behavior stub
+    +-- js/emergent-mechanics.js  Emergent game mechanics from player behavior
+
+    CI scripts (not browser runtime):
+    +-- scripts/guardrails.sh  Static analysis guardrails for game logic
+    +-- scripts/smoke.mjs      Playwright smoke tests
+
+    Reference prototypes (NOT loaded by runtime):
+    +-- docs/reference/npc-logic-prototype.js    NPC state machine prototype
+    +-- docs/reference/guardrails-prototype.js   Stat validation prototype
 ```
 
 ## Entry Points

docs/DEAD_CODE_AUDIT_2026-04-12.md

@@ -3,20 +3,15 @@ _2026-04-12, Perplexity QA_
 
 ## Findings
 
-### Potentially Unimported Files
+### Dead Code — Resolved (2026-04-15, Issue #192)
 
-The following files were added by recent PRs but may not be imported
-by the main game runtime (`js/main.js` → `js/engine.js`):
+The following files were confirmed dead code — never imported by any runtime module.
+They have been moved to `docs/reference/` as prototype reference code.
 
-| File | Added By | Lines | Status |
-|------|----------|-------|--------|
-| `game/npc-logic.js` | PR #79 (GOFAI NPC State Machine) | ~150 | **Verify import** |
-| `scripts/guardrails.js` | PR #80 (GOFAI Symbolic Guardrails) | ~120 | **Verify import** |
-
-**Action:** Check if `js/main.js` or `js/engine.js` imports from `game/` or `scripts/`.
-If not, these files are dead code and should either be:
-1. Imported and wired into the game loop, or
-2. Moved to `docs/` as reference implementations
+| File | Original | Resolution |
+|------|----------|------------|
+| `game/npc-logic.js` | PR #79 (GOFAI NPC State Machine) | **Moved to `docs/reference/npc-logic-prototype.js`** — ES module using `export default`, incompatible with the global-script loading pattern. Concept (NPC state machine) is sound but not wired into any game system. |
+| `scripts/guardrails.js` | PR #80 (GOFAI Symbolic Guardrails) | **Moved to `docs/reference/guardrails-prototype.js`** — validates HP/MP/stats concepts that don't exist in The Beacon's resource system. The `scripts/guardrails.sh` (bash CI script) remains active. |
 
 ### game.js Bloat (PR #76)
 

js/engine.js

@@ -142,6 +142,11 @@ function tick() {
     G.harmony += G.harmonyRate * dt;
     G.harmony = Math.max(0, Math.min(100, G.harmony));
 
+    // Clamp resources to prevent negative values from debuffs/Fenrir drain
+    G.ops = Math.max(0, G.ops);
+    G.trust = Math.max(0, G.trust);
+    G.compute = Math.max(0, G.compute);
+
     // Track totals
     G.totalCode += G.codeRate * dt;
     G.totalCompute += G.computeRate * dt;

js/tutorial.js

@@ -208,6 +208,23 @@ function renderTutorialStep(index) {
     // Focus the next button so Enter works
     const nextBtn = document.getElementById('tutorial-next-btn');
     if (nextBtn) nextBtn.focus();
+
+    // Focus trap: prevent tabbing outside the tutorial overlay
+    overlay._focusTrapHandler = function(e) {
+        if (e.key !== 'Tab') return;
+        const focusable = overlay.querySelectorAll('button, [href], [tabindex]:not([tabindex="-1"])');
+        if (focusable.length === 0) return;
+        const first = focusable[0];
+        const last = focusable[focusable.length - 1];
+        if (e.shiftKey && document.activeElement === first) {
+            e.preventDefault();
+            last.focus();
+        } else if (!e.shiftKey && document.activeElement === last) {
+            e.preventDefault();
+            first.focus();
+        }
+    };
+    overlay.addEventListener('keydown', overlay._focusTrapHandler);
 }
 
 let _tutorialStep = 0;
@@ -236,6 +253,9 @@ document.addEventListener('keydown', function tutorialKeyHandler(e) {
 function closeTutorial() {
     const overlay = document.getElementById('tutorial-overlay');
     if (overlay) {
+        if (overlay._focusTrapHandler) {
+            overlay.removeEventListener('keydown', overlay._focusTrapHandler);
+        }
         overlay.style.animation = 'tutorial-fade-in 0.3s ease-in reverse';
         setTimeout(() => overlay.remove(), 280);
     }