By default, a clone of the Atari game "Outlaw" is loaded. WASD/Arrow keys to move, Space/E to shoot. Shoot while moving to fire at an angle. These ricochet off the walls. Shoot the Outlaw before he shoots you!
CHIP-8 is a simple instruction set for making games. It has 35 instructions, 16 varibles, a 64x32 display, and a buzzer. (More info on Wikipedia.) Everything but CHIP-8 specs are by me! Have fun!