The left five LEDs represent the number of sides of the die and the right five LEDs represent the current roll. The values displayed by the LEDs are in binary if you tilt the Circuit Playground 90 degrees clockwise. The right most LED of either set is the lowest place digit of the value being represented. The left button toggles through the different dice and the right button rolls the current die. The available dice are 2, 4, 6, 8, 10, 12, and 20-sided dice. It can be useful if you're playing tabletop RPGs and forget your dice or just want a cool, hipster alternative to dice.