diff --git a/src/games/wolfenstein/WolfensteinLogic.js b/src/games/wolfenstein/WolfensteinLogic.js
index 049c86f..9979612 100644
--- a/src/games/wolfenstein/WolfensteinLogic.js
+++ b/src/games/wolfenstein/WolfensteinLogic.js
@@ -359,6 +359,68 @@ function isInMeleeArc(px, py, pAngle, tx, ty, range, arcRad) {
   return Math.abs(diff) <= arcRad / 2;
 }
 
+/**
+ * Flood-fills the map's floor cells into rooms: a maximal connected region
+ * of open (wallType 0) cells, where a door cell — whatever its live
+ * open/closed `slide` — always counts as a boundary, never as floor. That's
+ * why this can't just read `map.walls[y][x] > 0` on its own: stepDoors
+ * zeroes a door cell's wall-grid entry while it's fully open (see
+ * DOOR_WALL_TYPE's other callers), which is exactly right for
+ * movement/LOS/rendering but wrong here — two rooms joined only by a door
+ * must stay two rooms, open or shut, per alertEnemiesInPlayerRoom's
+ * "gunfire carries through the room, not through doorways" contract. So a
+ * door's cell is always excluded via `doors` (permanent x/y entries, unlike
+ * `slide`) regardless of what the live grid says at that cell right now.
+ * Cheap enough (every level here is well under 1000 cells) to just
+ * recompute on demand rather than caching on state.
+ */
+function computeRooms(map, doors) {
+  const doorCells = new Set(doors.map((d) => `${d.x},${d.y}`));
+  const blocked = (x, y) => doorCells.has(`${x},${y}`) || map.walls[y][x] > 0;
+  const roomOf = Array.from({ length: map.height }, () => new Array(map.width).fill(-1));
+  let nextRoom = 0;
+  for (let y = 0; y < map.height; y++) {
+    for (let x = 0; x < map.width; x++) {
+      if (roomOf[y][x] !== -1 || blocked(x, y)) continue;
+      const id = nextRoom++;
+      const stack = [[x, y]];
+      roomOf[y][x] = id;
+      while (stack.length) {
+        const [cx, cy] = stack.pop();
+        for (const [nx, ny] of [[cx + 1, cy], [cx - 1, cy], [cx, cy + 1], [cx, cy - 1]]) {
+          if (nx < 0 || ny < 0 || nx >= map.width || ny >= map.height) continue;
+          if (roomOf[ny][nx] !== -1 || blocked(nx, ny)) continue;
+          roomOf[ny][nx] = id;
+          stack.push([nx, ny]);
+        }
+      }
+    }
+  }
+  return roomOf;
+}
+
+/**
+ * A gunshot alerts every idle guard sharing the player's room, regardless
+ * of range/LOS/facing-cone — those only gate the "spotted visually" path in
+ * stepEnemyAI; this is "heard it," a separate trigger. Already-alert/
+ * chase/attack guards are left alone (nothing to escalate), and a shot
+ * fired from inside a door cell (roomOf has no entry for doorways
+ * themselves) simply alerts no one via this path.
+ */
+function alertEnemiesInPlayerRoom(state) {
+  const roomOf = computeRooms(state.map, state.doors);
+  const p = state.player;
+  const playerRoom = roomOf[Math.floor(p.y)]?.[Math.floor(p.x)] ?? -1;
+  if (playerRoom < 0) return;
+  for (const e of state.enemies) {
+    if (e.dead || e.state !== 'idle') continue;
+    if (roomOf[Math.floor(e.y)]?.[Math.floor(e.x)] === playerRoom) {
+      e.state = 'alert';
+      state.events.push({ t: 'enemyAlert', id: e.id });
+    }
+  }
+}
+
 export function fireWeapon(state, rules) {
   const p = state.player;
   const w = rules.weaponById[p.weapon];
@@ -390,6 +452,7 @@ export function fireWeapon(state, rules) {
     ownerId: 'player', x: p.x, y: p.y, angle: p.angle, weapon: w.id,
     speed: w.speed, damage: w.damage, hitRadius: w.hitRadius, ttlSec: w.ttlSec, friendly: true,
   });
+  alertEnemiesInPlayerRoom(state);
 }
 
 function spawnProjectile(state, rules, opts) {
diff --git a/src/games/wolfenstein/WolfensteinView.js b/src/games/wolfenstein/WolfensteinView.js
index 1fdae22..576362a 100644
--- a/src/games/wolfenstein/WolfensteinView.js
+++ b/src/games/wolfenstein/WolfensteinView.js
@@ -341,8 +341,9 @@ export default class WolfensteinView {
    * guard always shows it head-on regardless of viewing angle (attacking
    * guards don't move, so the player is almost always roughly in front of
    * them anyway). `flip` mirrors the single "facing right" pose for the
-   * left side — if left/right ever reads backwards in-game, flip the sign
-   * on the `rel > 0` line below, nothing else needs to change.
+   * left side — was `rel > 0` originally, but that read backwards in-game
+   * (2026-08-21), so it's `rel < 0` now. If it's ever wrong again, flip
+   * this one sign; nothing else needs to change.
    */
   _guardFacing(e, camera, now) {
     if (e.state === 'attack') return { frame: GUARD_FRAME.shoot, flip: false };
@@ -362,7 +363,7 @@ export default class WolfensteinView {
     if (absRel > (3 * Math.PI) / 4) {
       return { frame: walkOn ? GUARD_FRAME.backWalk : GUARD_FRAME.backIdle, flip: false };
     }
-    return { frame: walkOn ? GUARD_FRAME.sideWalk : GUARD_FRAME.sideIdle, flip: rel > 0 };
+    return { frame: walkOn ? GUARD_FRAME.sideWalk : GUARD_FRAME.sideIdle, flip: rel < 0 };
   }
 
   _ensureSprite(key, tex) {
diff --git a/tools/verifyWolfenstein.js b/tools/verifyWolfenstein.js
index 583ad40..2637c08 100644
--- a/tools/verifyWolfenstein.js
+++ b/tools/verifyWolfenstein.js
@@ -278,6 +278,52 @@ section('4. Enemy AI');
     check('a 2-waypoint route closes into a one-way loop, never reversing', cyclesForward, indices.slice(0, 9).join(','));
   }
 
+  // Gunfire alerts every idle guard sharing the player's room
+  // (alertEnemiesInPlayerRoom/computeRooms), independent of range/LOS/cone
+  // — and independent of whether a connecting door is open or closed, since
+  // a door is always a room boundary for this purpose. No L.tick() calls
+  // anywhere in this block, so nothing but fireWeapon's new room-alert path
+  // can move a guard out of 'idle' here — a clean isolation from the
+  // ordinary spot-the-player AI in stepEnemyAI.
+  {
+    const W = 11, H = 5;
+    const walls = [];
+    for (let y = 0; y < H; y++) {
+      const row = [];
+      for (let x = 0; x < W; x++) {
+        const border = x === 0 || y === 0 || x === W - 1 || y === H - 1;
+        const divider = x === 5 && (y === 1 || y === 3); // leaves (5,2) open for the door
+        row.push(border || divider ? 1 : 0);
+      }
+      walls.push(row);
+    }
+    const doors = [{ x: 5, y: 2, orientation: 'vertical' }];
+    const twoRoomLevel = (enemyX, enemyY) => ({
+      width: W, height: H, cellSize: 64, walls, doors, items: [],
+      playerStart: { x: 2.5, y: 2.5, angle: 0 },
+      enemies: [{ type: 'guard', x: enemyX, y: enemyY, facing: 180 }],
+      exit: { x: 9.5, y: 1.5, radius: 0.6 },
+    });
+
+    {
+      const state = L.createState(twoRoomLevel(3.5, 1.5), rules); // same room (left, x 1-4)
+      L.fireWeapon(state, rules);
+      check('gunshot alerts an idle guard sharing the room', state.enemies[0].state === 'alert', state.enemies[0].state);
+    }
+    {
+      const state = L.createState(twoRoomLevel(7.5, 1.5), rules); // other room (right, x 6-9), door closed
+      L.fireWeapon(state, rules);
+      check('gunshot does not alert a guard behind a closed door', state.enemies[0].state === 'idle', state.enemies[0].state);
+    }
+    {
+      const state = L.createState(twoRoomLevel(7.5, 1.5), rules); // same, door forced fully open
+      state.doors[0].slide = 1; state.doors[0].target = 1;
+      state.map.walls[2][5] = 0;
+      L.fireWeapon(state, rules);
+      check('gunshot does not alert a guard through an open door either', state.enemies[0].state === 'idle', state.enemies[0].state);
+    }
+  }
+
   // A dead guard stops acting and can't be hit/killed twice.
   {
     const level = { ...baseLevel, playerStart: { x: 1.5, y: 1.5, angle: 0 }, enemies: [{ type: 'guard', x: 3.5, y: 1.5, facing: 180 }] };