Use your mouse key to move your soul (the red dot). Dodge the balls and the boss itself. Press Z for some frames of immunity. Touch the white attack circle to deal damage to the boss. If your HP turns to 0, you lose! But, if you get the boss's HP to 0, You win!
UPDATES: *Update 1: Corner cubes has been added! *Update 2: Music, fighting and start screen has been added! *Update 3: Healing and a second boss has been added! *Update 4: Final attack has been added! CREDITS: Pixilab for the music (Ihatetuesdays)