what i liked: I liked that you even added levels and you increased the power of the player as they played. That felt very much like an rpg. I also liked that you killed the enemies slowly rather than all at once. This was an ambitious game for the time allotment I'd say!
what I would suggest: I'd suggest making the shooting a little faster. I'd find myself clicking over and over waiting before I could shoot again. If I could kill them quicker it would be more fun.
overall: I'd like to play this game more with slightly more polish. The gameplay loop has potential for being really fun!