Sloped belts hold their load with moving cleats (t42); sloped filters are downhill shaking screens (t43)

The magic grip is gone: cleats every 8 face cells, 6 grains tall, carry
pockets uphill (about 71 grains/s against 90 flat) and overflow rolls
back. Sloped filters always run downhill; grains travel by gravity and
a shake, and sorting stays exact. Drawing needs another pass.

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

src/ui/selection.js

@@ -47,6 +47,7 @@ function rotate() {
   else if (t === 'build') {
     const P = piece();
     if (pieceUsesWall(P)) cycleWall(1);
+    else if (P.filter && beltGrade(pieceCode(P))) return;
     else if (P.dirs) GAME.pieceDir[P.id] = ((GAME.pieceDir[P.id] || 0) + 1) % P.dirs.length;
     else return;
   } else if (t === 'drill') { tuneUnderCursor(); return; }
@@ -83,7 +84,7 @@ function setBrush(d) {
 // materials and mode travel separately, as GAME.filterCfg)
 function pieceV(P) {
   if (isWall(P.code)) return GAME.wallMat;
-  if (P.filter) return (GAME.pieceDir[P.id] || 0) << 7;
+  if (P.filter) return filterVariant(pieceCode(P), (GAME.pieceDir[P.id] || 0) << 7);
   return GAME.pieceDir[P.id] || 0;
 }
 function pieceExtra(P) { return P.filter ? { m: GAME.filterCfg.m.slice(), inv: GAME.filterCfg.inv } : undefined; }