code: function quadrant(point, node, fallback) {
  		if (point.x < node.x && point.y < node.y) return 1;
  		if (point.x > node.x && point.y < node.y) return 2;
  		if (point.x > node.x && point.y > node.y) return 3;
  		if (point.x < node.x && point.y > node.y) return 4;
  		return fallback;
  	}
docs: find basic quadrant using relative position of endpoint and block rectangle