Earthtongue is a “vivarium sim”, which lets us futz with an alien ecosystem, playing with fungus and invertebrates to shape the world. It's currently at a discount, but if you’re feeling creative, you can pay with fan art instead.
It's one of my absolutely favourite games. If you decide to play it, try not to read any guides, it's super fun to discover species and their behaviors on your own, which is kind of the focus of the game itself.

Happy holidays! ^ . ^