From 6fb0edeae05a13e8ef112efcd7125d0874559745 Mon Sep 17 00:00:00 2001
From: Alexander Whitestone <alexpaynex@gmail.com>
Date: Tue, 21 Apr 2026 10:37:33 -0400
Subject: [PATCH] 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
---
 js/engine.js   |  5 +++++
 js/tutorial.js | 20 ++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/js/engine.js b/js/engine.js
index 8a4bd40..049f165 100644
--- a/js/engine.js
+++ b/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;
diff --git a/js/tutorial.js b/js/tutorial.js
index 75008c4..f11ed35 100644
--- a/js/tutorial.js
+++ b/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);
     }