In its last of three announcements this week, Valve today unveiled a controller for its upcoming SteamOS and Steam Machines.

The Steam Controller will be available to those 300 gamers selected for the Steam hardware beta, which includes a prototype Steam Machine that's expected to ship later this year.

Unlike that Valve-developed Steam Machine, however, the Steam Controller will eventually go on sale to the public. There will be a few differences between the beta and final version of the controller, including the lack of a touch screen and wireless connectivity on the beta. The beta version will have four buttons instead of that screen, and will need a USB cable.

The Steam Controller includes two circular trackpads that will appeal to gamers who are used to inputs associated with the PC, and will allow for "far higher fidelity input" than previously possible, Valve said. In the center is the touch screen.

"Driven by the player's thumbs, each one has a high-resolution trackpad as its base," Valve said. "It is also clickable, allowing the entire surface to act as a button."

The Steam Controller will bring entire genres of gaming to the living room, Valve said: "RTS games. Casual, cursor-driven games. Strategy games. 4x space exploration games. A huge variety of indie games. Simulation titles. And of course, Euro Truck Simulator 2."

"In addition, games like first-person shooters that are designed around precise aiming within a large visual field now benefit from the trackpads' high resolution and absolute position control," Valve said.

The Steam Controller is a departure from the usual joystick-based controllers, and Valve said it needed to "find ways to add more physicality to the experience." Valve claims that the trackpads include "a new generation of super-precise haptic feedback" that allow for precise control.

The Steam Controller also includes a high-res, clickable touch screen. "When programmed by game developers using our API, the touch screen can work as a scrolling menu, a radial dial, provide secondary info like a map or use other custom input modes we haven't thought of yet," Valve said.

The device also includes 16 buttons, two of which are on the back.

For those tackling games that were created before the Steam Controller was developed, Valve added legacy mode, which "allows the controller to present itself as a keyboard and mouse." Players can come up with different configurations, which they can share with the community.

Earlier this week, Valve revealed its SteamOS, which will run on Steam Machines from third-party hardware manufacturers.