In the 1990s, the late chess grandmaster Bobby Fischer proposed a variant of the game that reduced this reliance on memory. Fischer suggested effectively randomising the starting positions of the pieces at the back of the board – apart from basic rules dictating where the bishops, rooks and kings must be relative to each other – with both white and black pieces taking on the same random arrangement. This format, called Chess960 for the number of possible starting positions, has recently ballooned in popularity, with players including former world champion Magnus Carlsen taking part in tournaments to better test their chess skills.