I saw this YouTube clip for a light weight drone, under a few ounces, with very impressive maneuverability. They used styrofoam for frame and taped the rotors and battery and the control chip to it. It maintains the balance, controls the four motors, pitch and yaw, lift and thrust, basically pilots the drone. And can do automatic stall recovery or aerobatics?

It seems like the most complex part of these drones, gyro, accelerometer, balance, aviation and navigation (all packed on a tiny board), is the most easy to make and cheapest part!

Can somebody explain to me how the this small flight command center feeds the controls of rotors? Does it have any sense of right side up, gravity? Can it sense the wind by measuring the drift?