Adds a simple regenerating health buffer. The shield's hp is consumed first before your own, and will regenerate slowly if you're not taking damage.

This is different from the energy shields already in Noita. The vanilla energy shields deflect projectiles while this still lets them hit you, but absorbs the damage.

You may configure all stats of the shield in mod settings.
By default, the shield has 15hp, starts regenerating after 10 seconds of no damage, and regenerates at a rate of 1hp/second.

*some ui code stolen from xs#7284