Loved the idea for the game, but I do feel like it was missing ambience without any music or sound effects. I did run into the issue where I couldn't actually use the buttons to upgrade anything and I think it's because the Zombies were taking all the money from spawning. 

Good concept. I like the game idea and the artstyle. Unfortunetly no music or soundeffects, and also pressing the upgrade button shouldnt spawn zombies, but apart from that, a nice experience.

Good game! I like the art style a lot, the gameplay is easy to understand! Maybe if the zombies couldn't spawn when I'm clicking the buttons, the game would've been better, but still, good job!