Terra
Terra lets you create and watch the interactions between creatures in a virtual terrarium. This projects inspiration comes from a textbook called Eloquent Javascript
Meet the Creatures
Creatures/Entities are defined as bundles of components. The components that make up an entity are defined in YAML, allowing for entities to be created and edited on the fly.
This is a rock. It does nothing but take up space.
This is a patch of grass. It takes in energy and when it has enough stored up will grow new grass next to it. If a patch of grass has too many entities surrounding it, it becomes suffocated and dies.
This is a dumb bug. It moves at random, hoping to come across grass to eat. If the bug finds a lot of grass, it builds up enough energy to lay an egg. If the bug can't find any grass, it starves.
This is an egg. Eventually, it hatches into a dumb bug.