This game is pretty much about walking and going from one level to another.
What makes it unique is that the author changed the default scale of the player model so the eye level is about 2.5 nodes high instead of the usual Minecraftish 2 nodes. This makes everything look more realistic, for example doors are 3 nodes high and 2 nodes wide.
Another cool aspect of the game are the textures that are less repetitive that usual Minetest/Minecraft textures.
Node design is simple and consistent - things like lamps, pipes, fences.
Levels are not boring because each represents another liminal space, for example theres a basement, a parking, a tunnel, a hotel and there are other more surrealistic spaces like for example the infinite swimming pool or the level with water and houses.
Exploring the spaces is driven mostly entirely by curiosity and a desire to find the way "out" - doors to another level.
Each level gives a strange discomfort that is the core of liminal space aesthetic.
Fun to "play" even though there's nothing "to do" other than exploring.