Noctis IV
Explore a procedurally generated galaxy full of unknown planets.
Somewhere around 1996, a developer who goes by Alex released the earliest version of Noctis. Noctis IV, the last official version has been supplemented with community-developed mods.
The game is pure exploration, with 70 billion stars to explore, catalog, and share notes with other players. Some planets are lifeless hunks of rock, while others are full of life, like that rabbit-kangaroo thing I took a snapshot of. The planet I found seemed to have some flying lifeforms as well, but I never got close enough to get a good look at it.
The controls are a bit weird, and the DOS-based nature of the game is showing its age, but Noctis remains one of the landmarks of procedurally generated exploration games.