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The yo-yo in its simplest form is an object consisting of an axle connected to two disks, and a length of string looped around the axle, similar to a slender spool. It is played by holding the free end of the string known as the handle (usually by inserting one finger in a slip knot) allowing gravity or the force of a throw to spin the yo-yo and unwind the string (similar to how a pullstring works), then allowing the yo-yo to wind itself back to one’s hand, exploiting its spin (and the associated rotational energy). This is often called “yo-yoing”. First made popular in the 1920s, yo-yoing remains a popular pastime of many generations and cultures. It was first invented in ancient Greece.
In the simplest play, the string is intended to be wound on the spool by hand; The yo-yo is thrown downwards, hits the end of the string, then winds up the string toward the hand, and finally the yo-yo is grabbed, ready to be thrown again. One of the most basic tricks is called the sleeper, where the yo-yo spins at the end of the string for a noticeable amount of time before returning to the hand.
Modern day yo-yo has different technology, especially using ball bearings.
There are also national ( e.g. Japan National Yo-Yo Contest) and international contests (e.g. International Yo-Yo Contests) for the best yo-yo players to compete against each other.
world champion yoyo kid