The controls are simple, the presentation is neat and the shooting feels good! However, I didn't feel like playing any more after the sixth or seventh waves, as by that point I felt like I had seen eveything the game had to offer. More enemy variety would be a first step toward a more engaging game! Also, I suggest removing blood or giving the option to turn it off, as it causes huge FPS drops, and disabling spawns near the player to prevent mindless spawnkilling - or, alternatively, making the enemies temporarily invincible but harmless upon spawning.