First room has serious rendering issues on Firefox (Fedora Linux) with walls disappearing and some geometry becoming lines going to some point in infinity.
Otherwise atmosphere and quality looks great, especially for a tech demo.
Oooh, I think I know why. First room uses img tags for the walls. Image tags (and canvas tags) do not play well in 3D contexts. For example they ignore depth sorting and rely on z-index. So you cannot properly depth sort them. Now you might wonder why I picked img tags for lvl1, and then divs for lvl2. Profiling showed reduced mem usage for img tags and I thought I 'd take advantage of that optimization. (premature optimization and all that I guess!)
Interesting observation. Would it be very complicated to add an option to select img or div based rendering?