Thanks for the feedback! We used the Three.js WebGL library and a custom-built game engine for the various interactions, pathfinding and game logic. We modeled the scenes in Blender and SideFX Houdini, and also baked lightmaps with Blender.
Nothing specific regarding mobile but we worked on rendering optimizations quite a bit to make the experience smooth. Most notably the render pipeline is based on MRT (Multiple Render Targets) which renders multiple frames at the same time, which is great when doing post-processing stuff. Also we made sure to keep the number of draw calls quite low by merging static objects. There is also a lot of culling going on, hiding rooms that are not visible.
We'll probably post more technical details on X in the coming days/weeks, be sure to follow us if you're interested.
I was impressed that it is present there. I would expect camer to fly directly to target location.