It's fine, but i didn't really like the initial stages. The leveldesign is not really optimal. 

The game felt the best when i was firing guns and running through. But one hit, and the powerup/gun is gone. So instead of playing fast, walking slowly and killing anyhting that comes on display is the best strategy.

Having the gun/powerups as lives is a great idea. But really. It should be the last hit, instead of the first. Like in Spyro the dragon,; after 3 hits. Spark goes away. That way the player would get to play more with game arsenal, without resoring to a cowardly strategy like me.