Leanback plays the videos based on your feeds and recommendations and it's controlled entirely with a keyboard's arrow and enter keys. Pressing up or down displays a search bar, lets you browse various content categories, and also gives access to basic video controls. The remaining buttons let you navigate or select items nothing fancy, but it's all you really need.
For now, Leanback has been added to the growing list of features on TestTube. You can try it out by visiting youtube.com/leanback. In other company news, YouTube has also launched a new site for mobile users (m.youtube.com), with features including a more touch-friendly interface as well as more functions from the main site such as favorites and ratings. You can watch a video detailing that here.