Really cool game. I really liked the graphics, art style and the different types of enemies. One thing I would for sure improve is the difficulty. Make sure the first few levels are pretty easy, so that players can explore and learn the mechanics. Keep in mind that you do a lot of play testing when developing the game and you get pretty good in it. If it feels too easy for you it is usually right for new players.
Congratulations to this nice game. Had fun playing it!