Illusion walls shimmer until YOU test them (rules rev 29)

Per the owner's design — and truer to a real table, where the cast is
public: every illusion wall's location is open knowledge, rendered as a
shimmering wall to any player whose eyes have not yet ruled on it.
Testing is an explicit act: tap the shimmer (or bump into it) and a
modal explains the 50/50 and offers 'Roll to test your eyes' — the new
testIllusion command rolls once, then the wall either hardens or
dissolves for you alone. Nobody's verdict is moved by watching someone
else stroll through (the Q3WZ mystery: an automaton walking through
its own round-1 fake). Untested walls block movement and sight without
consuming RNG; the pre-29 lazy belief roll is preserved for stored
games. Automatons doubt free shimmers on their best crossing before
spending any card on that wall.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0138A8CjeQRpvzKxuMfz1Bqc

packages/web/src/App.svelte

@@ -10,7 +10,7 @@
   import { scheduleFx, type BoardFx } from "./fx";
   import { CREATURE_ART, objectArt, TERRAIN_ART, tokenArt } from "./art";
   import { local } from "./local.svelte";
-  import { allCardDefs, cardDef, isNumberCard, isPermanentDuration, SIDES, stepTarget, cellKey, isMovableObject, sightedCellsFor, stackSightTrace, type GameView, eligibleCellsFor } from "@wizwar/engine";
+  import { allCardDefs, cardDef, isNumberCard, isPermanentDuration, SIDES, stepTarget, cellKey, edgeKey, isMovableObject, sightedCellsFor, stackSightTrace, type GameView, eligibleCellsFor } from "@wizwar/engine";
   import type { CardInstance, Side } from "@wizwar/engine";
 
   net.connect();
@@ -637,11 +637,17 @@
       }
     }
     // Adjacent but blocked? Send the move anyway — unlocked doors, mist-body
-    // and pass-through-wall are resolved server-side.
+    // and pass-through-wall are resolved server-side. A shimmering illusion
+    // in the way asks for the belief test first instead.
     for (const side of SIDES) {
       const n = { x: me.position.x + (side === "E" ? 1 : side === "W" ? -1 : 0),
                   y: me.position.y + (side === "S" ? 1 : side === "N" ? -1 : 0) };
       if (cellKey(n) === cellKey(cell)) {
+        const k = edgeKey(me.position, side);
+        if (view.illusionEdges[k] === "untested") {
+          illusionPrompt = illusionEdgeParts(k);
+          return;
+        }
         dispatch({ type: "move", direction: side });
         return;
       }
@@ -930,6 +936,19 @@
     clearSelection();
   }
 
+  // A shimmering illusion wall, tapped or bumped: offer the belief test.
+  let illusionPrompt = $state<{ cell: { x: number; y: number }; side: Side } | null>(null);
+  function illusionEdgeParts(key: string): { cell: { x: number; y: number }; side: Side } {
+    const [kind, coords] = key.split(":") as [string, string];
+    const [x, y] = coords.split(",").map(Number) as [number, number];
+    return { cell: { x, y }, side: kind === "V" ? "E" : "S" };
+  }
+  function rollIllusion() {
+    if (!illusionPrompt) return;
+    dispatch({ type: "testIllusion", cell: illusionPrompt.cell, side: illusionPrompt.side });
+    illusionPrompt = null;
+  }
+
   let pickChoice = $state(false);
   function pickUp() {
     if (treasuresHere.length > 1) { pickChoice = true; return; }
@@ -1119,6 +1138,30 @@
     </div>
   {/if}
 
+  {#if illusionPrompt}
+    <div class="scrim attack-scrim" role="button" tabindex="-1"
+      onclick={() => (illusionPrompt = null)} onkeydown={() => {}}>
+      <div class="attack-notice" role="dialog" aria-label="a shimmering wall" tabindex="-1"
+        onclick={(ev) => ev.stopPropagation()} onkeydown={() => {}}>
+        <div class="attack-title">That wall shimmers strangely…</div>
+        <div class="attack-power">
+          Someone conjured an ILLUSION WALL here. Whether YOUR eyes are fooled
+          is a 50/50 roll — once. Believe it, and it is stone to you until
+          dispelled; see through it, and you may walk it like open floor.
+          Other wizards' eyes rule for themselves.
+        </div>
+        <div class="attack-actions">
+          {#if isYourTurn}
+            <button class="stamp primary" onclick={rollIllusion}>Roll to test your eyes</button>
+          {:else}
+            <span class="attack-power">— you can test it on your turn —</span>
+          {/if}
+          <button class="hint-cancel" onclick={() => (illusionPrompt = null)}>leave it be</button>
+        </div>
+      </div>
+    </div>
+  {/if}
+
   {#if faqCardId}
     <Faq cardId={faqCardId} onclose={() => (faqCardId = null)} />
   {/if}
@@ -1503,6 +1546,7 @@
           ghostSlots={relocateGhosts}
           onGhostClick={clickGhostSlot}
           onCellPeek={(c) => peekAt(c)}
+          onIllusionClick={(cell, side) => (illusionPrompt = { cell, side })}
           {litCells}
           {sightTrace}
         />