I really like this game! The shooting is very satisfying, the enemies are great, and it's quite a challenge to get to the tokens. My best run was only 3 tokens; overall I did find it just a little bit too difficult, especially with zombies spawning on top of you sometimes and surprising you around corners. Some sound effects to indicate nearby zombies would really help, and the flares would be more useful if they lasted longer. Upgrades would also be fun. But it's already a fun game and the visuals are solid. Great work!
PS: One final suggestion, I think your title image actually undersells the game and would be better with a real screenshot in it.