The device contains a spring, a method of electric generation (linear motor, piezoelectric, etc.), a spinning mass, and an electric motor. The device is plugged in until the mass is spinning at an appropriate speed (let's call it 12,000 rpm). The user unplugs device, mounts device, and bounces. There is no fear of falling over, as it is self-balancing. However, if the user is not bouncing fast enough, she will begin to precess. Herein lies the fun. Bounce too fast and you precess in one direction, too slow and you precess in the other.-- Worldgineer, Jan 05 2004 Gyro Stilettos http://www.halfbake...ea/Gyro_20StilettosInspired by [FarmerJohn] [Worldgineer, Oct 04 2004, last modified Oct 05 2004] How would it spinning too fast be bad - unless you exploded the disc...-- my-nep, Jan 05 2004 Not bad, just dizzy. Using the law of conservation of momentum (angular momentum in this case), if you make the disc spin faster in one direction in a closed system then something else (everything but the disc) must spin faster in the other direction.-- Worldgineer, Jan 05 2004 ...and you DON'T want to be around when it spins down...-- phoenix, Jan 05 2004 I was expecting a Greek sandwich with LEDs that bounced up and down....terribly disappointed....-- normzone, Jan 05 2004 I feel a little ill just thinking about it. +-- Detly, Jan 05 2004 random, halfbakery