Thanks for reminding me of the game that was never finished. -_-
Voxel Quest is (let's be honest!) probably more of a research project than a game. It is an attempt to explore new areas in rendering, procedural generation, simulation, and AI. At this point, it is entirely free and I work on it as a hobby in my spare time. -https://www.voxelquest.com
This one looks like fun, though. I'll add it to the backlog.