Thank you for playing!
So basically, if the player hurts an enemy, they also hurt themselves, and vice versa. Also if the crystal is hurt, the player is hurt, and the enemy that attacked the crystal is hurt.
It was supposed to be a risk/reward game where killing enemies made it easier to defend the crystal but put you closer to death so if we you did mess up you're more likely to fail. Admittedly we didn't' balance it very well.