Kick Lucifers Ass

Shoot demons to get mana. Fire mana bombs at Lucifer. You can't carry reserve ammo, you can only swap guns.

Shoot: Left click

Fire mana bomb: Right click.

Jump: Space. You get a super-jump every 3 seconds.

Swap Guns: E

You can also waste mana bombs to blow-back demons, but be careful, ammo is limited.

EDIT: Source assets are up so you can check the timestamps.