To check if a tile is a 'topmost' tile, check if there is a tile directly above it. If not, then change it's frame.
This could be done using 'Overlapping at Offset':[code]is 'Tile' overlapping 'Tile' at offset (0,-1)'[/code]This will move the 'Tile' up a pixel and test for overlap. Inverting this condition will effectively test whether it's the topmost tile or not.
For bottom and sides use offsets (0, 1), (-1, 0), (1, 0) respectively.
If you can figure out (roughly) how your tiling engine works, the best approach would be to tap into its array to figure out if there's a tile above the one you are testing. That would be the easiest and the most straightforward.Dalal2013-07-17 15:29:51