The Minimal Arcade Machine (MAM) was part of the Hardware Hacking Village at CypherCon 3.0. The idea was to build the simplest arcade possible. After many prototypes, we came up with a design that has 15 LEDs, two buttons and uses the ATtiny85.
If you were not able to make it to CypherCon 3.0, you will find the build document here along with the usage document here. You will also need the game code, which is on GitHub here.