Art and challenge needs improvement.
Art may be improved a lot, the windows sounds, the "plant and zombies" zombies, and the main character seems like I dont remember who from Resident Evil. The charas dont look bad but could look better.
The main character moves pretty slow compared to the zombies, which makes the game harder and funnier, so that's up to you if later on the game the hero could improve his stats. And talking about that... maybe the hero shouldn't be able to buy most of the weapons by only surviving level one. If you want the player to be playing more levels, maybe you should make him wait and "suffer" a little more before being able to access the coolest weapons.
The main recipe for games is challenge and reward... h ttp://www.youtube.com/watch?v=n_ATFQX hMaM.
This game is not bad for a start, but there are still things to improve the "gaming experience". Keep up the good work.