All controls can be customized in the Settings screen.

Key Function
Mouse Navigate menus
WASD Movement. W will make you look (and shoot) up, and S will make you fall through certain platforms.
Navigate menus (not implemented for all menus).
Space Jump.
 J  Melee weapon. Every melee weapon has a ground combo attack, a mid-air attack, and a dashing attack.
 K  Gun. Hold down to fire rapid-firing weapons; press to fire non-rapid-firing weapons. Every gun can be fired straight, up, or down (only in midair).
 L  Dash. When dashing, you can pass through enemies safely.
Return/Enter Pause
Confirm menu choice.
F11 Toggle fullscreen.

Tips and Tricks

Wall sliding/jumping: hold one of the movement buttons towards a wall to slide on it. You can use either of your weapons while doing so. You can jump while sliding to climb up any vertical surface.

Combos with slow weapons: If you use a slower melee weapon in the air, land during your move, and attack again immediately, you'll pull off two hits faster than swinging while standing still.

Rocket jumping: Firing any gun down while falling will propell you upwards. You can, for example, use the rocket launcher to get an extra jump with the right timing, or use the rotoblaster to slow your descent.

See the in-game instructions page for more.