Goonslingers has a dual health system based on the player mass and the purity of it. 

The ammo is related to the health system as the player are shooting portions of their own mass.

This health system follows these rules:

• When you shoot you lose some mass as you are projecting a portion of your current mass.
• When you get shot you gain mass as it gets added to yours.
• If the mass added is from an ally, it increases how pure your mass is.
• If the shot comes from an enemy, it decreases the purity of your mass as the enemy mass is toxic for yours.

There are some diagrams about the health system, the power ups and the controls in the game, just before starting a new game and in the pause menu.