Function walk

packages/examples/src/examples/platformer-matter/createGame.ts:158–196

(c: Container | Renderable)

			// they can rest on the map2 pyramid platforms.
			let allPlatformBits = 0;
			const walk = (c: Container | Renderable) => {
				const children = (c as Container).children;
				if (!children) return;
				for (const child of children) {
					if (child.type === "platform") {
						const width = child.width ?? 0;
						// skip degenerate platforms (zero-width / missing geometry)
						// — they'd build a zero-area body that matter can't
						// resolve a contact for.
						if (width > 0) {
							adapter.updateShape(child, [
								new Rect(0, 0, width, PLATFORM_THICKNESS),
							]);
							const bit = nextPlatformBit;
							nextPlatformBit <<= 1;
							allPlatformBits |= bit;
							adapter.setCollisionType(child, bit);
							// Mask: PLAYER (for one-way pass-through, driven
							// by per-frame mask updates on the player) and
							// ENEMY (so slimes can stand on the map2 pyramid
							// platforms). Coins are static sensors with their
							// own broad-phase filter — they don't need to see
							// platforms.
							adapter.setCollisionMask(
								child,
								collision.types.PLAYER_OBJECT | collision.types.ENEMY_OBJECT,
							);
							oneWayPlatforms.push({
								renderable: child,
								top: child.pos.y,
								bit,
							});
						}
					} else if (child.type === "slope") {
						adapter.setSensor(child, true);
					}
					walk(child);
				}
			};
			walk(_app.world);

			// Second pass: extend each enemy's mask to include every