To show something fun right away:
I got pretty fair using SVGs to map boundaries:
as well as to map "portals" between screens. Animations via CSS properties, animated PNGs for sprites, built-in music support (HTML5 audio), etc., all made it possible to actually walk around, go from room to room, and investigate objects the way we're used to:
This was a fun exercise, and it runs well in Chrome, but it's only a handful of rooms from the main house. My other goal was to play with a sort of mini-game that was a new story. Here are some screenshots from that:
Title Screen: http://imgur.com/NU4redI
Map (used to go from location-to-location): http://imgur.com/vxP5k7H
Walking around: http://imgur.com/6G3CHjt
Just posting because I'm curious what others think.