That was fun and frustrating :D The main mechanic was fun to play with :] The asset choises also fits very well.
I think this game can benefit greatly from paralax scrolling. You should definetly take a look at that. The game needs some balancing in its current state its a bit hard. Also i noticed that when enemies die the explosion they leave behind kills the player if they touch it. I dont know if this was intensional but this makes the game more harder to play :/ Lastly i think the "Quit" button in the main menu is not working.
Overall other then these small issues i had a good time with this one. I would like to play again if you decide to update the game :D Great work !