# Defining Units¶

A world can have the following types of units:

• Critters: Animals that will move around the map at random

• Immovables: Trees, rocks, artifacts and eye candy

• Resources: Mineable map resources like fish, water, coal, …

• Terrains: The base of the landscape. Meadows, mountains, water…

The definitions for the world’s units are located in the subdirectories of data/world. Each unit needs to have an init.lua file, which will load the unit to be used in the game.