Within Steam's "Big Picture Mode," games are shown with a half- or full-controller to signify partial- or full-controller support, respectively.
However, many of the games listed as "partial controller support" I've played for hours with a gamepad, without ever needing to use a mouse or keyboard. These include
- Prototype 1+2
- Batman: Arkham Asylum and Arkham City
- Beat Hazard
- LA Noire
- The Last Remnant
And many others. So, what exactly determines if a game has full- or only partial-controller support?