I worked on a project before that explores using non-traditional UI on the web:

https://overwebs.ruph.in (warning - sound and high bandwidth)

It emulates a game UI, and uses background video to simulate physical movement when navigating between pages. It also incorporates some controls that are unusual for normal web applications like keyboard controls (shortcuts like 'Esc' to go back, 'Enter' to open chat).

It's a pretty old and very experimental project so some stuff is in a semi-broken state. I should revisit it sometime and clean up.