I suggest that you play the post-jam version since it fixes some playability issues.
An angel had the mission to purify lost souls in hell.
As angels can't go freely in hell; he decided to control a demon to achieve his goal.
You are this demon: good luck!
The souls you gather are your energy.
You start with just one soul.
If you loose it: run as fast as you can to get one or you die.
Hell is full of danger, your energy will leave you quickly.
Press C to Jump
Press X to Draw your Soul Sword and jump a little higher.
Be careful of using it because it draws souls out you body.
The post-jam version requires at least a 1280x640 screen to be played. If you have a smaller resolution, play the original version.