Diablo2D — Shadows of Tristram: complete browser ARPG

- Isometric canvas renderer (depth-sorted, FOV/fog, additive lighting)
- 3 classes x 20 skills, 4 acts x 4 floors + boss lairs, torment I-X
- Diablo-style loot: rarities, affix tiers, 14 legendaries, vendor, stash
- Rogue camp with 6 NPCs: Charsi/Akara/Kashya/Cain/Gheed/storage
- NPC quest chain (accept -> hunt -> turn in) with rewards & gating
- Procedural WebAudio SFX + generative music, EN/VI localization
- Saves, settings, waypoints, hardcore mode, PWA manifest
- 93-assertion headless suite + browser E2E via CDP

js/game/fov.js

@@ -0,0 +1,45 @@
+/* ============================================================
+ * Diablo2D — fov.js : raycast visibility & fog of war
+ * ============================================================ */
+'use strict';
+window.D2 = window.D2 || {};
+(function (D2) {
+
+  const RAY_COUNT = 160;
+
+  /**
+   * Update world.visible / world.explored from (cx, cy) within radius.
+   * world must expose: w, h, transparent(x,y), visible(Uint8), explored(Uint8)
+   */
+  function compute(world, cx, cy, radius) {
+    const { w, h } = world;
+    world.visible.fill(0);
+    const r2 = radius * radius;
+
+    const mark = (x, y) => {
+      if (x < 0 || y < 0 || x >= w || y >= h) return;
+      const i = y * w + x;
+      world.visible[i] = 1;
+      world.explored[i] = 1;
+    };
+
+    mark(cx, cy);
+
+    for (let i = 0; i < RAY_COUNT; i++) {
+      const ang = (i / RAY_COUNT) * Math.PI * 2;
+      const dx = Math.cos(ang), dy = Math.sin(ang);
+      let x = cx + 0.5, y = cy + 0.5;
+      for (let d = 0; d < radius; d += 0.5) {
+        x += dx * 0.5; y += dy * 0.5;
+        const tx = x | 0, ty = y | 0;
+        if (tx < 0 || ty < 0 || tx >= w || ty >= h) break;
+        const ddx = x - cx - 0.5, ddy = y - cy - 0.5;
+        if (ddx * ddx + ddy * ddy > r2) break;
+        mark(tx, ty);
+        if (!world.transparent(tx, ty)) break;
+      }
+    }
+  }
+
+  D2.fov = { compute };
+})(window.D2);