From a concept standpoint, the game is pretty awesome
You are a zombie destroying other humans, which is probably very creative
The gameplay is smooth and straightforward with a lot of tapping to kill
Progression of enemies tells a story of how you are a zombie wreaking havoc
Improvements and Suggestions;
Enemies don't deal constant damage which is weird but works well balancing
Instead of shooting bullets what about you spawn other zombies
You can have other abilities like bombs, missiles
The Graphics is readable but can be improved by adjusting the lighting and a few colour changes