Walls you know are lies stand as ghosts

A wizard who has seen through an illusion no longer walks toward empty
air where the board shows a dashed ghost: the ray records the first
known-illusion edge it crosses without stopping, and the renderer
stands a wall there at one-fifth opacity, violet ripple running through
it, drawn over the sprites so bodies show through its breath. Untested
illusions get the same tell the board gives — a faint shimmer on their
solid face, maybe stone, maybe not — while a believed illusion stays
honest brick. The workshop rehearses it with ?illusion=H:2,8.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/web/src/fpv/FirstPerson.svelte

@@ -219,12 +219,22 @@
     // ghost into real corridors the unrolled space happens to overlap.
     const zbuf = new Float64Array(W);
     const warpedCol = new Uint8Array(W);
+    // Known illusions: the ray passes, but a translucent ghost of a wall
+    // stands at the crossing — drawn after the sprites so bodies show
+    // through it, shimmering so nobody mistakes it for stone.
+    const ghosts: { col: number; depth: number; u: number; worldU: number }[] = [];
     for (let col = 0; col < W; col++) {
       const rayAngle = facing + Math.atan((col / W - 0.5) * 2 * Math.tan(FOV / 2));
       const hit = castRay(view, ex, ey, rayAngle, doors);
       const depth = hit.dist * Math.cos(rayAngle - facing); // no fisheye
       zbuf[col] = depth;
       warpedCol[col] = hit.warped ? 1 : 0;
+      if (hit.ghost) {
+        ghosts.push({
+          col, depth: hit.ghost.dist * Math.cos(rayAngle - facing),
+          u: hit.ghost.u, worldU: hit.ghost.worldU,
+        });
+      }
       const wallH = Math.min(H * 2.5, H / Math.max(depth, 0.05));
       const top = half - wallH / 2;
       const tex = textures[hit.kind] ?? textures.wall!;
@@ -250,6 +260,13 @@
         ctx.fillStyle = `rgba(190,150,255,${Math.max(0, swirl)})`;
         ctx.fillRect(col, top, 1, wallH);
       }
+      if (hit.kind === "wall" && hit.edge && view.illusionEdges[hit.edge] === "untested") {
+        // The same tell the board gives: an untested illusion's face
+        // shimmers faintly — maybe stone, maybe not.
+        const tell = 0.06 + 0.05 * Math.sin(time / 260 + hit.worldU * 13);
+        ctx.fillStyle = `rgba(190,160,255,${Math.max(0, tell)})`;
+        ctx.fillRect(col, top, 1, wallH);
+      }
       if (hit.kind === "door" && hit.edge && view.doorStates[hit.edge] === "jammed") {
         // A jammed lock seethes: a rusty seal pulsing across the wood.
         const seethe = 0.10 + 0.08 * Math.sin(time / 160 + hit.worldU * 22);
@@ -322,6 +339,21 @@
       if (s.glow) ctx.globalAlpha = 1;
     }
 
+    // The ghosts of walls you know are lies: drawn over everything at
+    // their columns, thin as breath, rippling.
+    for (const gh of ghosts) {
+      const gHft = Math.min(H * 2.5, H / Math.max(gh.depth, 0.05));
+      const gTop = half - gHft / 2;
+      const tex = textures.wall!;
+      ctx.globalAlpha = 0.2;
+      ctx.drawImage(tex, Math.min(tex.width - 1, gh.u * tex.width), 0,
+        Math.max(1, tex.width / 96), tex.height, gh.col, gTop, 1, gHft);
+      ctx.globalAlpha = 1;
+      const ripple = 0.10 + 0.07 * Math.sin(time / 200 + gh.worldU * 11 + gHft * 0.01);
+      ctx.fillStyle = `rgba(190,160,255,${Math.max(0, ripple)})`;
+      ctx.fillRect(gh.col, gTop, 1, gHft);
+    }
+
     // A whisper of vignette holds the torchlit mood together.
     const vig = ctx.createRadialGradient(W / 2, half, H * 0.35, W / 2, half, H * 0.95);
     vig.addColorStop(0, "rgba(0,0,0,0)");