Rubik's Cube
cal. 395
Level of arithmetic, recreation and happy (TvF).
Wikipedia says:
By 1981, Rubik's Cube had become a craze, and it is estimated that in the period from 1980 to 1983 around 200 million Rubik's Cubes were sold worldwide.
Level of arithmetic, recreation and happy (TvF).
Wikipedia says:
By 1981, Rubik's Cube had become a craze, and it is estimated that in the period from 1980 to 1983 around 200 million Rubik's Cubes were sold worldwide.