I always enjoy seeing your progress and your demo is really well done and polished so much that you should probably move onto making levels if you're not already.
You can't have your first slide obstacle that is just the size of your slide, getting stuck is no fun.
The boss slam attack was feeling downright broken with how fast and unwiduppy it is, but the design was cool and the boss fight was fun, once i got over the frustration.
The final form was sort of bad, because you can only attack in front of you (i see another comment mentioning ranged attacks, i don't know they existed!), but if there's a ranged attack, i guess he's okay. I ended standing in palce and punching him while soaking up the damage.
The lightwhip seems a tad bit too OP, it's fast, straight and deadly to almost everything.
Overall i really liked it, except fro the antialiased text in the main menu (also really bright menu, jeez)