Drag the boxes around. We'll run hitTest() logic inside an onDrag, highlighting "droppable" elements but only when at least 50% of their surface area overlaps (you can change the overlapThreshold variable to whatever you want). Then, in an onDragEnd, we'll do the same and make any intersecting "droppable" elements flash. Read the comments in the code to find out how to test for the mouse/touch overlapping an element instead.