I built a BB-8 robot, as seen in the new Star Wars trilogy. This was the second robot I built, and I started it right after the trailer for episode 7 was released. It moves by tilting a large mass and compensating for the horizontal deflection with motorized wheels that run along the interior of the ball. There is also a servo to turn the head, which is mounted on top of the sphere with powerful magnets. My budget was under $200, so the actuall ball is a lamp globe. Because of this, the robot had to assembled like a ship-in-a-bottle, so it is made up of 3 separate pieces. I'll post some pictures and videos of BB-8 once I get the chance.