Three upgrades for the pistol:

damage
fire rate

and... bullet??

Why not explain what that means.

good game but gets easy after a while.

good game

needs more depth tho...
later part of the game i was just holding space and right directional
final boss was easier than the first boss
the only monster that posed a challenge was the shooting devil(and his double shooting brother)

Very good game

This game is done very well. Though as other have said, The game is well ballanced until rocket is gotten and the game is usually rather easy from there.

Keep up the good work.

Gets too easy later in the game

The beginning levels are well balanced but once you get the rocket upgrades you can just hold down space and right arrow the entire level and your guy will go around in circles blowing everything away without trying.

Nice graphics though!