Make your way to the exit while collecting as many souls as you can. Jump using X and toggle ghost-mode using C. While in ghost-mode you can go through walls and take over enemies by touching them. When you take over an enemy you get their properties such as flight and double-jump.

Controls:
[X] to jump
[C] for Ghostmode
[P] to pause (and see the controls)
[R] to restart
[SHIFT] to suicide/go back to the level select screen
[+] to turn up the volume
[-] to turn down the volume
[0] to mute/unmute all sounds
[9] to mute/unmute the music