Control your character with AD or Arrow Keys, jump with W/Space/Up, and use the mouse to aim and shoot (or switch control schemes in the options). As you acquire more guns, use QE or 1-4 or the mouse wheel to switch between them. After collecting diamonds, open the upgrades menu with tab or escape to upgrade your guns and skills to help conquer your foes.

Shoot, upgrade, conquer enemies, defeat bosses, acquire achievements, collect gems, all in an attempt to save yourself and your gun from the clutches of the evil Professor.