GooKeeper is a gameplay module which is closely related to the game "Slime Rancher". Here, the player is left in the Goo World, and has to earn a living by catching, feeding, and breeding gooeys of different kinds to make a "Goo Zoo" which simulated visitors can visit. This module first started as a game design concept by SuperSnark, which was later taken up by l0ftyWhizZ as a Google Summer of Code 2018 project.
Here's a video demonstrating gooey capturing mechanic as well as the zoo visitor spawn system:
This video demonstrates the newly developed gooey breeding system:
For in-depth information about the different gameplay mechanics and equipment, visit the Wiki.