Hello! I didn't build this on my own, i used the instructions for building from Hitechnic.com, but i thought i'd post it anyway. So its a two wheel robot that balances on the two wheels. It uses the gyro sensor to stay upright. The other sensor is a completely useless accelerometer sensor whos in this case is to balance out the robot. my dad and I modified our downloaded program so it would fit our bot. (its supposed to run on the irremote, but i don't have that, thats why we modified it). Now it goes around on its two wheels. It also makes a good treat butler for my doggie :) See the video to see how that works.