Rubik's cube

A Rubik's cube was a six-sided puzzle toy that was popular on Earth in the 1980s, and remained a cult favourite afterwards. Each side of the cube contained nine stickers of a unique color in a 3-x-3 arrangement. Any three segments of squares could be scrambled out of order vertically or horizontally by using a pivot mechanism to turn them. The cube would then be solved by resetting all the sides to a solid colour. Though a Rubik's cube could daunt the untrained solver, skilled users discovered and created special algorithms that could be applied to solve the cube in a methodical manner, while limiting the moves it took for them to complete the puzzle.

Toshiko Sato had a Rubik's cube at her work station in the Hub. Owen Harper would mess it up when she wasn't looking, but she would solve it each time, infuriating him. (PROSE: Another Life)

Luke Smith owned a Rubik's cube that he kept on his bedside table. (TV: The Nightmare Man)

In 2011, the Eleventh Doctor toyed around with a Rubik's cube he found in George's bedroom and was unable to solve it. (TV: Night Terrors) He later found one while in the hotel constructed on the prison ship and solved it. (TV: The God Complex)

In 2050, Starkey once fiddled with a Rubik's cube in his room in Gryffen Manor. (TV: Jaws of Orthrus)