Loose grains and solid ground look different: a seam on the rock, pebbly lighter grains (t33)

- Smooth look: natural ground gets a soft seam where loose grains meet it; packed grains keep a
  pebble texture and are slightly lighter. Pixel look and thermal lens: the same idea per pixel.
- play.py: the F-on-a-mold toast check records toasts the key press makes instead of counting
  the ones on screen, which failed when an older toast expired at the same moment.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/render/smooth-shaders.js

@@ -176,9 +176,11 @@ void main() {
     float band = 1.0 - smoothstep(0.5, 0.9, M);
     float lit = dot(nrm, normalize(vec2(-0.5, -1.0)));
     tc *= 1.0 + 0.42 * lit * band;
-    // the outline follows where ground and grains meet open space, never where rock meets gravel
+    // Keep the air outline; a softer, screen-width seam also separates rock from loose grains.
     float dm = (M - 0.5) / fwM;
     tc *= mix(0.4, 1.0, smoothstep(0.5, 1.4 + zp * 0.08, dm));
+    float dt = (F.r - 0.5) / fwT;
+    if (nc == 1 && pw > 0.0) tc *= mix(0.65, 1.0, smoothstep(0.0, 1.5, dt));
     C = mix(C, tc, smoothstep(-0.6, 0.6, (F.r - 0.5) / fwT));
   }
 
@@ -200,10 +202,13 @@ void main() {
     }
     float cover = np == 4 ? 1.0 : 1.0 - smoothstep(1.0 - px / gr, 1.0 + px / gr, best);
     if (closed && F.r < 0.5) cover = 1.0;
+    // Pebbles stop at the rock face so they cannot paint over its thin seam.
+    cover *= 1.0 - smoothstep(-0.6, 0.6, (F.r - 0.5) / fwT);
     if (cover > 0.0) {
       float r2 = min(1.0, dot(gd, gd));
       vec3 n3 = normalize(vec3(gd * 0.85, sqrt(1.0 - r2) + 0.25));
-      float sh = np == 4 ? 0.9 + 0.08 * vn(w * 0.9) : 0.8 + 0.3 * max(0.0, dot(n3, normalize(vec3(-0.45, -0.8, 0.6))));
+      float sh = 0.98 + 0.18 * max(0.0, dot(n3, normalize(vec3(-0.45, -0.8, 0.6))));
+      sh *= mix(1.0, 0.94, smoothstep(0.7 - px * 0.2, 1.15 + px * 0.2, best));
       vec3 pc = (np == 4 ? (k0.rgb * wq.x + k1.rgb * wq.y + k2.rgb * wq.z + k3.rgb * wq.w) : gc) * sh;
       if (!closed) pc *= mix(1.0, 0.72, smoothstep(0.7, 1.0, best));
       C = mix(C, pc, cover);

src/render/world.js

@@ -59,12 +59,24 @@ function drawWorld() {
       }
       const i = yw + x, m = mat[i], nz = noiseB[i] - 128;
       const T = temp[i];
+      // Also used by the thermal lens, which always draws in pixels.
+      let looseShade = 1;
+      if (!sm && m !== EMPTY && !builtForLight(i, x, y)) {
+        if (PH[m] === PH_POWDER) looseShade = 1.1 + nz * 0.00065;
+        else if (PH[m] === PH_SOLID && (
+          (x > 0 && PH[mat[i - 1]] === PH_POWDER && !part[i - 1]) ||
+          (x + 1 < W && PH[mat[i + 1]] === PH_POWDER && !part[i + 1]) ||
+          (y > 0 && PH[mat[i - W]] === PH_POWDER && !part[i - W]) ||
+          (y + 1 < H && PH[mat[i + W]] === PH_POWDER && !part[i + W])
+        )) looseShade = 0.72;
+      }
       let r, g, b;
       if (lens) {
         const ti = thermIdx(T);
         if (m === EMPTY) { r = tl[ti] * 0.55; g = tl[ti + 1] * 0.55; b = tl[ti + 2] * 0.55; }
         else { const v = (COLR[m] + COLG[m] + COLB[m]) / 3 * 0.25; r = tl[ti] * 0.78 + v; g = tl[ti + 1] * 0.78 + v; b = tl[ti + 2] * 0.78 + v; }
         const p = part[i];
+        r *= looseShade; g *= looseShade; b *= looseShade;
         if (p && ((x + y) & 1)) { r = r * 0.7 + 40; g = g * 0.7 + 40; b = b * 0.7 + 40; }
         if (fv < 255) { r *= fv / 255; g *= fv / 255; b *= fv / 255; }
         px[row + bx] = 0xff000000 | ((b > 255 ? 255 : b) << 16) | ((g > 255 ? 255 : g) << 8) | (r > 255 ? 255 : r);
@@ -93,6 +105,7 @@ function drawWorld() {
       else {
         const v = nz * CVAR[m] * (sm ? (PH[m] === PH_SOLID ? 0 : grain * 0.35) : grain) / 128;
         r = COLR[m] + v; g = COLG[m] + v; b = COLB[m] + v;
+        r *= looseShade; g *= looseShade; b *= looseShade;
         if (m === FIRE) { const f = (life[i] & 15) * 6; r = 255; g = 120 + f; b = 30 + f * 0.5; }
         else if (m === WATER && !sm) { const s = ((x * 3 + y * 5 + (anim >> 2)) & 15) === 0 ? 14 : 0; r += s; g += s; b += s; }
         else if (m === BELTL || m === BELTR) {