The craziest part is that it executes on my iPhone SE 2020 in Safari. Textures work, shading works, pretty insane. I even managed to break a block.
The trickiest issue is input, since the "look around with your mouse" interaction maps very poorly on a mobile platform where "mousemove" implies touching / clicking.
We plan to eventually figure out a mobile-optimize UX, but we will most likely prioritize improving the performance first.