topDownJumping.qst
TopDownJumper.z
jump.wav
land.wav
It could be improved upon (it could see if you actually have the flippers, for one thing), but it's a start.
If you want to play around with it, it shouldn't be much different from _L_'s. Just be sure to set the "Draw Over" flag, set up the combos properly, and give it the right arguments.
You'll notice each screen in the demo has one of the corners covered by layer 3. That's where Link actually is when you jump; the one you see is just the FFC. That's what the arguments are for: they're the X and Y coordinates of where to stash him.
(Edit: There. Slightly less buggy.)
(Edit 2: Slightly less buggy still. I laugh at your pathetic attempt to complete a download!)
(Edit 3: Added shadow and slower diagonal movement. Didn't change solidity checking to match, though. Is Boolean XOR not working? Wouldn't compile - accused me of trying to cast bools to floats.)