Raspberry Pi board morphs into a gaming device with the Hyper Keyboard Pi
If you want to turn your humble Raspberry Pi board into a full-fledged handheld console/PC that you can game on or use for general consumption of media, then you might want to consider a custom kit like the Hyper Keyboard Pi. The finished build measures 14 cm x 10 cm and features a full QWERTY keyboard and even a game pad.
The Hyper Keyboard Pi requires a compatible display in the form of Pimoroni’s HyperPixel 4.0 screen, which comes in both touch and non-touch variants. Obviously, users will have to supply their own Raspberry Pi 3 Model B single-board computer, battery, USB cable, etc. Access to and skill with a 3D printer can assist with making the finished product look as polished as possible.
It may not rival a PS4 or Xbox One X, or even a GPD Win 2, but the Raspberry Pi with Hyper Keyboard Pi kit fitted does have a certain appeal, especially to those who like to build devices themselves and enjoy the tinkering aspect of the project. However, as pointed out by Liliputing, once you add in the cost of the display, RPi board, and other required accessories, you might want to just save up a bit more and pick up a Nintendo Switch instead.
Source(s)
Booth (in Japanese)