Screw tubes use all their lanes: grains spread sideways inside a tube

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

src/sim/conveyors.js

@@ -91,6 +91,18 @@ function filterRun(b) {
 
 // A cell a grain can be pushed into: empty, or liquid or gas that simply trades places with it
 function roomFor(j) { const t = mat[j]; return t === EMPTY || PH[t] === PH_GAS || PH[t] === PH_LIQUID; }
+// Cross one tube block, far lanes first; corners retain their liquid/gas swaps.
+function tubeSpread(c, x, y, sx, sy, intake = false) {
+  const p = part[c], bx = x >> 2, by = y >> 2;
+  for (;;) {
+    const nx = x + sx, ny = y + sy;
+    if (nx < 0 || ny < 0 || nx >= W || ny >= H || (nx >> 2) !== bx || (ny >> 2) !== by) break;
+    const j = ny * W + nx;
+    if (part[j] !== p || occ[j] || (intake ? mat[j] !== EMPTY || stamp[j] === tickStamp : !roomFor(j))) break;
+    move(c, j, x, y, nx, ny); c = j; x = nx; y = ny;
+  }
+  return c;
+}
 // An empty screw cell draws in loose material from behind it or from its sides
 // (not from the cell it pushes into), so a tube end sitting in a pile feeds itself.
 function tubeIntake(i, p, dx, dy) {
@@ -109,6 +121,7 @@ function tubeIntake(i, p, dx, dy) {
     if (pj >= P_TU && pj <= P_TR) continue; // other tube cells move their own contents
     if (pj === P_GRATE || pj === P_FILTER) continue;
     move(j, i, nx, ny, x, y);
+    if (ox !== -dx || oy !== -dy) tubeSpread(i, x, y, -ox, -oy, true);
     return;
   }
 }

src/sim/machine-tick.js

@@ -126,6 +126,22 @@ function machinesTick() {
       const x = i % W, y = (i / W) | 0;
       // a sideways screw carries its load along the bottom: grains settle into empty lanes below
       if (flat && y + 1 < H && part[i + W] === p && roomFor(i + W) && !occ[i + W]) { move(i, i + W, x, y, x, y + 1); continue; }
+      if (!flat) {
+        let own = 0, shifted = false;
+        const end = dy < 0 ? (y & ~3) : (y | 3);
+        for (let yy = y; dy < 0 ? yy >= end : yy <= end; yy += dy) if (PH[mat[yy * W + x]] === PH_POWDER) own++;
+        const side = ((tick >> 1) + i) & 1 ? 1 : -1;
+        for (let c = 0; c < 2; c++) {
+          const sx = c ? -side : side, xx = x + sx, j = i + sx;
+          if ((xx >> 2) !== (x >> 2) || part[j] !== p || !roomFor(j) || mat[j] !== EMPTY || occ[j] || stamp[j] === tickStamp) continue;
+          let load = 0;
+          for (let yy = y; dy < 0 ? yy >= end : yy <= end; yy += dy) if (PH[mat[yy * W + xx]] === PH_POWDER) load++;
+          // Include this grain: a strict gap prevents a sideways step being undone next beat.
+          if (own <= load + 1) continue;
+          move(i, j, x, y, xx, y); stats.moved++; shifted = true; break;
+        }
+        if (shifted) continue;
+      }
       const nx = x + dx, ny = y + dy;
       if (nx < 0 || ny < 0 || nx >= W || ny >= H) continue;
       const j = i + dj;
@@ -143,15 +159,7 @@ function machinesTick() {
       move(i, j, x, y, nx, ny); stats.moved++;
       if (tube && pj !== p) {
         // turning a corner: keep going across the new tube's width so every lane fills
-        let c = j, cx = nx, cy = ny;
-        const bxj = nx >> 2, byj = ny >> 2;
-        for (;;) {
-          const ex = cx + dx, ey = cy + dy;
-          if (ex < 0 || ey < 0 || ex >= W || ey >= H || (ex >> 2) !== bxj || (ey >> 2) !== byj) break;
-          const e = ey * W + ex;
-          if (part[e] !== pj || !roomFor(e) || occ[e]) break;
-          move(c, e, cx, cy, ex, ey); c = e; cx = ex; cy = ey;
-        }
+        tubeSpread(j, nx, ny, dx, dy);
       }
     }
   }