Retro gaming is a massively popular Raspberry Pi application, and while loading your favourite old video games onto an SD card is pretty straightforward, building the physical shell of a gaming system can be daunting for those of us without 3D printers or design skills of any kind. PiBoy Mini bridges that gap by providing partially-assembled devices to their customers. The rest is BYORP: bring your own Raspberry Pi.
Gpi case 2 would be a cheaper purchase. Only lacking a joystick and two other buttons, which really only os helpful for psx games which run okay at best on cm4 hardware.