[Ilya Titov] has made a game console. Not just any game console, but an extremely small ATtiny85-based console suitable for putting on a key ring and assembled into a very professional product with PCB and 3D printed case. This is a project that has been on the go since 2014, but the most recent update is a new version designed for tighter and more easy assembly.
All construction is through-hole rather than SMD, and aside from the ATtiny85 the console uses an OLED screen, piezo buzzer, tactile switches and a handful of passive components. Power comes from a single CR2032 coin cell which sits under the screen. Best of all the PCB design is available as a PDF and the 3D printed case can be found on Thingiverse.
There are two games for the console, as well as the Breakout clone whose code is in the 2014 piece linked above he’s written UFO Escape, an obstacle-avoiding side-scroller. You’ll have to burn both game and 8MHz internal clock bootloader to the ATtiny85 yourself. There are no cartridges with this console, though if the processor sits in a DIP socket the game can be changed over simply by swapping processors programmed with the appropriate game.
He’s produced a full assembly video with some UFO Escape gameplay thrown in, shown here below the break.