left/right move, c/up to jump, x to shoot, esc to pause – custom controls can be set in the pause menu
Gathering a new powerup will overwrite your current powerup. If you hang on to a powerup instead of getting new ones, you can level it into better, more powerful forms.
If needed, you may press the down key to drop your powerup and return to it later. Be careful though, after so long it will disappear!