I like how the entrances, surfaces, and windows are disassociated from their placements with the parallax floatiness. It feels more like collection of architectural instances and boundaries in memory than pieces that are available for procedural generation or assembly. The technique reminds me of Night Thoughts.
Feels like the bg elements are cut-outs, tied to strings and suspended.
I like the tile that's used for darkness or fog in the lower right, how they're arranged like someone covering a surface with post-it notes, and how each one updates at a slightly offset interval.