gistfile1.js

//else we search for an entity with Mouse component
if (!closest) {
	q = Crafty.map.search({ _x: x, _y: y, _w: 1, _h: 1 }, false);

	for (l = q.length; i < l; ++i) {
		if (!q[i].__c.Mouse || !q[i]._visible) continue;

		var current = q[i],
			flag = false;

		//weed out duplicates
		if (dupes[current[0]]) continue;
		else dupes[current[0]] = true;

		if (current.mapArea) {
			if (current.mapArea.containsPoint(x, y)) {
				flag = true;
			}
		} else if (current.isAt(x, y)) flag = true;

		if (flag && (current._z >= maxz || maxz === -1)) {
			//if the Z is the same, select the closest GUID
			if (current._z === maxz && current[0] < closest[0]) {
				continue;
			}
			maxz = current._z;
			closest = current;
		}
	}
}