A "Rattleback" is a semi elliptical object that spins on its axis in one preferred direction due to an offset centre of gravity.

If spun in the opposite direction it will rock from instability, stop and then reverse direction.

Tapping one end of the rattleback will also cause it to spin in the preferred direction.

Note: the rattleback must be spun whilst resting on the curved face, not the flat face.

Ages 5+