This guy basically recreated no-man's sky as a Doom mod... with nearly the same amount of content. It took him 3 weeks, and he hasn't even played No Man's Sky.

https://www.youtube.com/attribution_link?a=qVQKu2DD46k&u=%2Fwatch%3Fv%3DacM7PElWI_4%26feature%3Dshare