I know its been forever, but you should definitely make this into a full length game with multiple bosses and stuff. My only complain is that the character shadows are too circular - they should be ovals that fit the perspective of the map/scene, and probably semi-transparent. Other than that this is a visual/auditory/game mechanic perfection.
Ideas:
Make the puck faster and faster on subsequent hits if not enough time has passed between hits - sort of modeling physics of table tennis.
Allow player to "body slam" the enemy boss (or be body slammed) if they're both close to the divider line
Boss idea: perhaps more than one enemy boss at a time would make things harder
Perhaps allow aiming the puck by swinging with a combination of up/down arrow keys, or the right/left arrow keys, etc