Small changes sometimes have a big impact. At the end of the 15th century, for example, a far-reaching change was made to the rules of chess. The queen, which until then had only been allowed to move one square diagonally, was given freedom of movement and could now move any number of squares diagonally as well as vertically and horizontally. Thus, the queen was considerably upgraded among the six different chess pieces and became the most powerful piece. The change in the rules meant that chess players had to adapt a new playbook. Chess remained chess, and yet it became a completely different game.