Oh man, this game makes me remember those times when I play the Call of Duty Zombies arcade mode (Dead Ops Arcade). This game has potential to moving on, something like Dead Ops Arcade and better.
The gameplay, you got it. But you can buff the amount of zombies, spawn bullets when there are zombies of that color. An alternative to kill zombies when you don't have bullets, power-ups, etc...
Good Job for all the team!.