Revamped energy system

[SuperFola]

Currently, the player gains 1 energy ever turn, and can use it for anything: walking, attacking, picking up an object, using an object... The same (at least it should, iirc) applies to monsters which can see the player (if they are in the player field of view, they can gain energy ; this is a small optimization to avoid updating things you can't see).

It could be interesting

• to have actions that don't need energy to be used
• to be able to gather energy to cast bigger fireball (by not moving for a couple turns for example)
• to display the energy level
• to find other interesting uses of the energy