I made a little authoring system & corresponding html5 runtime a couple years ago, specifically for first-person adventure games.  It solved the key issue lacking in my first engine from long ago - AGE ( - which was a lack of authoring environment.  In Narrativ you can just upload your scenes and wire them all together really quickly.  The latest version also supports uploading PSD files with lots of logic for showing/hiding layers and parallax scrolling.  The downside is that I only support true/false flags, and no complex logic or scripting, which means that more sophisticated puzzles are difficult to author.  Also, I haven't added back full motion video yet :)