Most of these don't work to some degree on mobile.
The Very Large Hotdog (VLHd), I used 383 slack emoji to make a picture of a hotdog.
Track, using object-tracking and CSS transforms to embed (interactive!) DOM elements onto a video of real space.
IBM, a PowerPC terminal rendered in-browser. I tried to make it look as real as possible, the crt flickers, the letters glow and are skewed, and there's a reflection on the terminal.
City, an animation (all CSS, no WebGL!) inspired by the computer graphics from the landing scene in Escape From New York (which was done entirely without CG!).
IRC in AR in a mobile browser, using ar.js I embedded #csc on freenode into AR
Recycle, a small joke website riffing on my friend's insistence that everyone recycle.