Cool idea. Great animation. The main character, while a pile of leaves, definitely *feels* beefy. I don't know how that's accomplished, but I'm impressed.
The enemy is not very aggressive--he spends most of his time blocking, and only occasionally attacks. Also, a sound effect should play upon victory! Finally, a thematic quibble: green leaves don't typically fall off trees; it might make more sense if the leaves making up the main character were yellow, orange, and red.