Too bad I couldn't play it on my phone because of the scaling issues, feel like I didn't get the proper experience, but I did play it on my PC and I must say I see nothing wrong with this concept. This is one of those games I could see myself just chilling with while being bored on public transportation, so yeah perfect concept for a mobile game! And I actually really like the zombie design, did you make them yourself?
Overall the game is actually really solid, just needs some scaling optimization, audio implementation and a bit of juice to the zombie hit :)