Its a little bit slow.
I like it, the graphics are fair play, different enemies are good play against and the upgrading system is always good to have.
I notice though that when you move (for me) the Frame rate drops dramatically and when you stop moving, everything seems fine. Have you made the game where the whole stage moves when you move? If so, i would suggest the vcam - developed by Adam Philips and his counterpart.
Otherwise, it is a pretty good game.