Custom helper (in combination with cursorAt)
We are draggables..
..whose z-indexes are controlled automatically..
..with the stack option.
Provide feedback to users as they drag an object in the form of a helper. The
helper option accepts the values 'original' (the draggable object moves with the cursor), 'clone' (a duplicate of the draggable moves with the cursor), or a function that returns a DOM element (that element is shown near the cursor during drag). Control the helper's transparency with the
To clarify which draggable is in play, bring the draggable in motion to front. Use the
zIndex option to set a higher z-index for the helper, if in play, or use the
stack option to ensure that the last item dragged will appear on top of others in the same group on drag stop.