That's super clever! So you're basically using a 2D level render as a texture and then warping it in the shader to form the Mobius effect, right? Would love to know more about how you handled the vertex displacement part was it all procedural or did you model the base mesh first and just apply twist via shader?
Yes, the 2D grid level is rendered as a texture and mapped onto several simple 2×1 strip meshes (made with Blender), and the shader bends each strip into the ring and applies the twist. Player movement and keys/doors logic run on the 2D layer, and the result is re-rendered to the texture every frame.