What is considered the world's top selling single toy of all time?

The Rubik's Cube is a 3-D combination puzzle invented in 1974 by Hungarian sculptor and professor of architecture Ernő Rubik. It is widely considered to be the world's best-selling toy.

On the original classic Rubik's Cube, each of the six faces was covered by nine stickers, each of one of six solid colors: white, red, blue, orange, green, and yellow. Some later versions of the cube have been updated to use colored plastic panels instead, which prevents peeling and fading. In models as of 1988, white is opposite yellow, blue is opposite green, and orange is opposite red, and the red, white, and blue are arranged in that order in a clockwise arrangement. On early cubes, the position of the colors varied from cube to cube. An internal pivot mechanism enables each face to turn independently, thus mixing up the colors. For the puzzle to be solved, each face must be returned to have only one color. Similar puzzles have now been produced with various numbers of sides, dimensions, and stickers, not all of them by Rubik.

Although the Rubik's Cube reached its height of mainstream popularity in the 1980s, it is still widely known and used. Many speedcubers continue to practice it and similar puzzles; they also compete for the fastest times in various categories. Since 2003, the World Cube Association, the international governing body of the Rubik's Cube, has organized competitions worldwide and recognizes world records.