Decent retro platformer.
Why is a Space Ninja using a gun? One would expect a laser sword or homing shuriken or something of the like.
Besides that nitpicking, I've only got two real things to comment on; first off, how come your lasers don't travel past your screen but the enemies fire does? Secondly, this could really use a couple boss battles.
Oh, and some timed weapons upgrades would be a nice addition as well.