SlugSprites
Library, made to simplify assigning and manipulating sprites to custom slugcat with as little as single json config. Main focus of the mod is on defining sprites with multiple customizable colours.
Has API in case you want to enhance your looks even further.
Check remix menu for hot reloading of sprites and configurations.
Wiki with tutorial and examples on how to set it up for you custom scug and API are at: https://github.com/glebi574/rw-mods/wiki/SlugSprites
