Nice job, I've always wanted to be an intellect devourer protecting myself from a virus infestation! I think you did a great job balancing the level waves, they had a reasonable increase in difficulty to make each level a little harder than the last without spiraling out of control.
After five or six levels the game started to feel a little repetitive, so I might have liked to have seen new enemy types or maybe the opportunity for temporary powerups.
The addition of the dwindling lighting as you ran out of lives was a nice touch, good job!