HTML5 version of its Unreal Engine tech demo Epic Citadel. Currently, the project is optimized for Firefox Nightly version 23 or above, so make sure your browser is up to spec before you check it out.
While Epic Citadel currently crashes in Chrome, Google's developers are looking into a fix. Internet Explorer does not support current versions of WebGL. Epic Citadel launched as a free download for iOS devices back in 2010, paving the way for Chair's release of the hit Unreal-powered action game Infinity Blade later that year.