Browser Game Engine

If I recall correctly Game Maker exports to HTML5, that's an engine

If HTML5 is not a hard constraint, you can also use Unity to create Webplayer builds.

Proprietary player like Flash, ugly, I know.

With Unity 5 though you get WebGL Support.

Pixi is interesting. You'll need a little sound engine with it as it's only for video. Great tutorial here:

http://www.yeahbutisitflash.com/?p=5226

Hi, do you know WiMi5?

It´s easy to use and learn and totally based in HTML5