Use WASD or the arrow keys to move.
Left-clicking will shoot cheese.
Right-clicking will shoot sardines, but beware: you only have five for every boss. [After every few cats you destroy, you will get one sardine back.
Use the space bar to shoot your Mega Blue Cheese. After one shot, you must wait until it charges back up. Every fifty clicks will enable you to shoot it again.
Left shift makes you sprint. It recharges every ten seconds.
The "T" key allows you to slow down time to one tenth of a second.
The "E" key hides Julian.
That's about it!