ehm

workshop/steps/12-overlap/overlap.ts

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+import { type AABB, EPSILON, moveAndSlide, type Vec } from "./given.ts";
+
+/**
+ * How to push `a` OUT of `b`, by the smallest possible single-axis move.
+ *
+ * Returns the push as a vector to ADD to a's position, or null if the boxes
+ * don't strictly overlap (merely touching edges is not overlapping).
+ *
+ * There are four ways out (left, right, up, down) — measure all four
+ * distances and return the shortest one. See the README.
+ */
+export function penetrationVector(a: AABB, b: AABB): Vec | null {
+	const outLeft = a.x + a.w - b.x;
+	const outRight = b.x + b.w - a.x;
+	const outUp = a.y + a.h - b.y;
+	const outDown = b.y + b.h - a.y;
+
+	const minX = Math.min(outLeft, outRight);
+	const minY = Math.min(outUp, outDown);
+
+	if (minX > 0 && minY > 0) {
+		return minX > minY
+			? { x: 0, y: outDown > outUp ? -minY : minY }
+			: { x: outLeft > outRight ? minX : -minX, y: 0 };
+	}
+
+	return null;
+}
+
+/**
+ * moveAndSlide, but immune to the overlap trap: first push `box` out of any
+ * wall it is already inside (plus an EPSILON of slack, same idea as the
+ * backoff in the loop), THEN run the normal sweep loop from the safe spot.
+ *
+ * Everything you need is penetrationVector above and given.ts.
+ */
+export function safeMoveAndSlide(box: AABB, v: Vec, walls: AABB[]): Vec {
+	for (const wall of walls) {
+		const pv = penetrationVector(box, wall);
+		if (pv) {
+			box.x += pv.x > 0 ? pv.x + EPSILON : pv.x - EPSILON;
+			box.y += pv.y > 0 ? pv.y + EPSILON : pv.y - EPSILON;
+		}
+	}
+
+	return moveAndSlide(box, v, walls);
+}