Sloped belts and filters, laid by a 45° drag (t40)

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

src/sim/pieces.js

@@ -6,9 +6,22 @@
 const BS = 4;
 const BP_WALL = 1, BP_BELT = 2, BP_TUBE = 3, BP_SHAFT = 4, BP_GRATE = 5, BP_GATE = 6, BP_FILTER = 7, BP_PIPE = 8, BP_PUMP = 9, BP_OUTLET = 10, BP_GRIND = 11, BP_SAW = 12, BP_PRESS = 13, BP_RACK = 14;
 const BP_SLOPE_BL = 15, BP_SLOPE_BR = 16, BP_SLOPE_TL = 17, BP_SLOPE_TR = 18;
+// The shape is independent of the direction: reversing a belt never flips its face.
+const BP_BELT_UP = 19, BP_BELT_DOWN = 20, BP_FILTER_UP = 21, BP_FILTER_DOWN = 22;
+function isSlopeBelt(c) { return c >= BP_BELT_UP && c <= BP_FILTER_DOWN; }
+function isFilter(c) { return c === BP_FILTER || c === BP_FILTER_UP || c === BP_FILTER_DOWN; }
+function isBelt(c) { return c === BP_BELT || c === BP_BELT_UP || c === BP_BELT_DOWN; }
+function beltGrade(c) { return c === BP_BELT_UP || c === BP_FILTER_UP ? -1 : c === BP_BELT_DOWN || c === BP_FILTER_DOWN ? 1 : 0; }
+function slopeShape(c) { return isSlopeBelt(c) ? (beltGrade(c) < 0 ? BP_SLOPE_BR : BP_SLOPE_BL) : c; }
+function beltFaceY(c, bx, by, x) { return by * BS + (beltGrade(c) < 0 ? 3 - (x - bx * BS) : beltGrade(c) > 0 ? x - bx * BS : 0); }
+function beltDirection(c, v) {
+  const d = isFilter(c) ? (v & 128 ? 1 : -1) : (v ? 1 : -1), g = beltGrade(c);
+  return g ? (g * d < 0 ? 'up-' : 'down-') + (d > 0 ? 'right' : 'left') : d > 0 ? 'right' : 'left';
+}
 function isSlope(c) { return c >= BP_SLOPE_BL && c <= BP_SLOPE_TR; }
 function isWall(c) { return c === BP_WALL || isSlope(c); }
 function slopeCell(c, x, y) {
+  c = slopeShape(c);
   if (c === BP_SLOPE_BR || c === BP_SLOPE_TR) x = 3 - x;
   if (c === BP_SLOPE_TL || c === BP_SLOPE_TR) y = 3 - y;
   return y >= x;
@@ -30,7 +43,12 @@ function filterRec(c) {
   for (let m = 1; m < NMAT; m++) if (filterable(m)) pass[m] = (k.m.includes(m) ? 1 : 0) ^ k.inv;
   return { m: k.m, inv: k.inv, pass };
 }
-function filterPassAt(m, j) { const c = filterCfg.get((((j / W) | 0) >> 2) * BW + ((j % W) >> 2)); return c ? c.pass[m] : 0; }
+function filterPassAt(m, j) {
+  let b = (((j / W) | 0) >> 2) * BW + ((j % W) >> 2);
+  if (!isFilter(blockP[b])) { const owner = slopeSealOwner(j); if (owner >= 0) b = owner; }
+  const c = filterCfg.get(b);
+  return c ? c.pass[m] : 0;
+}
 function filterInfo(b) { const c = filterCfg.get(b); return c ? { m: c.m.slice(), inv: c.inv } : { m: [], inv: 0 }; }
 function sameFilter(a, b) { return a.inv === b.inv && a.m.length === b.m.length && a.m.every((m, k) => m === b.m[k]); }
 // loose material -> the solid it becomes in a wall block
@@ -52,11 +70,11 @@ const PIECES = [
   { id: 'wall', code: BP_WALL, name: 'Wall block', kind: 'block', variants: 'wall',
     desc: 'A solid block. Diagonal drags make a sloped face; T flips it. For one block, T cycles square and four slope corners. R picks the material: a square costs 16 grains or 2 bars; a slope costs 8 grains or 1 bar.' },
   { id: 'belt', code: BP_BELT, name: 'Belt', kind: 'block', cost: [[CASH, 12]], dirs: ['left', 'right'],
-    desc: 'Carries loose grains and bars resting on top of it, left or right, in a layer up to a block deep. Water and other liquids drain through it.' },
+    desc: 'Carries loose grains and bars resting on top of it, left or right, in a layer up to a block deep. Water and other liquids drain through it. Drag diagonally to make a sloped belt that carries up or down.' },
   { id: 'tube', code: BP_TUBE, name: 'Screw tube', kind: 'block', cost: [[CASH, 25]], dirs: ['up', 'right', 'down', 'left', 'up-right', 'down-right', 'down-left', 'up-left'],
     desc: 'A turning screw that draws in loose grains and whole bars and pushes them along, four grains wide. Water and other liquids run straight through it; the screw never carries them. Drag a line to set its direction, including diagonals. R turns a single tube. Join either end to tubes or belts. Copper softens around 1000°C.' },
   { id: 'filter', code: BP_FILTER, name: 'Filter', kind: 'block', cost: [[CASH, 40]], dirs: ['left', 'right'], filter: true,
-    desc: 'A stretch of belt with a mesh in it. Put it in a line of belts and it joins them as one belt. Pick materials and a mode: drop them through and carry everything else along, or carry them and drop the rest. Liquids drain through.' },
+    desc: 'A stretch of belt with a mesh in it. Put it in a line of belts and it joins them as one belt. Pick materials and a mode: drop them through and carry everything else along, or carry them and drop the rest. Liquids drain through. Drag diagonally to make a sloped filter that carries up or down.' },
   { id: 'shaft', code: BP_SHAFT, name: 'Shaft', kind: 'block', cost: [[LWOOD, 8]], hidden: POWER_FREE,
     desc: 'Carries power between machines. Wooden, so keep it away from fire.' },
   { id: 'grate', code: BP_GRATE, name: 'Grate', kind: 'block', cost: [[LCLAY, 8]],
@@ -97,6 +115,8 @@ const PIECES = [
 const PIECE_BY_ID = {}, PIECE_BY_CODE = [];
 PIECES.forEach((p, i) => { p.index = i; PIECE_BY_ID[p.id] = p; if (p.code) PIECE_BY_CODE[p.code] = p; if (p.kind === 'machine') { p.w = p.bw * BS; p.h = p.bh * BS; } });
 for (let c = BP_SLOPE_BL; c <= BP_SLOPE_TR; c++) PIECE_BY_CODE[c] = PIECE_BY_ID.wall;
+for (const c of [BP_BELT_UP, BP_BELT_DOWN]) PIECE_BY_CODE[c] = PIECE_BY_ID.belt;
+for (const c of [BP_FILTER_UP, BP_FILTER_DOWN]) PIECE_BY_CODE[c] = PIECE_BY_ID.filter;
 // power per grain of belt / tube (a block is 16 grains)
 const BELT_POWER = 0.03, TUBE_POWER = 0.125, FAN_POWER = 6;
 const WHEEL_K = 0.32, ENGINE_K = 40;