Great game. 10/10
I really liked it. Not at first as much but the powerups made it much better. Theres a lot more to be done with this idea. Im sure youve thought about making more powerups. Also, maybe if you controlled your concussion gun with the mouse it would make things more free ranged. 360 angles you can shoot vs 8.. Keep up the good work.
p.s. if you liked this game you would like the flash version of portal.