BetterSpellWheel draws its wheel artwork the first time the game starts with the
mod enabled, and keeps it in a subfolder per artwork version (v2/skill.png,
v2/spell.png, v2/center.png, ...). The files are generated by Scripts/art.lua;
delete them to have them redrawn. PNGs directly in this folder are left from
0.4.5 and older and are no longer used; they are safe to delete.
