https://youtu.be/Edl2PefQmEQ
I don't know if it's subgame, mod, or world. It's a custom world, with its own mod, using a purpose designed subgame, this one not intended for this world only.
Changelog
Spoiler
»Added tons of backstage
»Added chamber a03
»Added Trees! (Because it's warmer)
»Added THE NEW! Handheld 20kg / 44lb Anvil
»Added 終 to the "end screen" (means "end")
»Reworked the announcement devices
»Reworked some of the voice lines
»Changed fog colour from bitter blue to zorin os suicide blue
»Closed off the elevator shaft
»Has not added furniture to the relaxation cabin
»Yet to create the toilet
10/04 ⇒ 13/04
»Reworked chamber bridges
»Reworked chamber a02
»Reworked voice over
»Added music
»Added more voice over
»Added footsteps
»Added pedestal
»Added mesecon compatibility to KiHa read-only
»Added pressure plate