woah!
The maker/s of this are legends, I have seen quite a few 3D type games done for pico-8 and some nice 'engines' for them (I have also failed at using them as I'm new to Pico lol), but this is epic.
To unwind I still always find myself plying doom (1993) or the modded versions even when there's more modern and graphically stunning games out there.. the simple style is just fun/enjoyable even to this day and 'Doomero Inc' and other modders still put-out quality content.