Definition: A diagonal is a chain of at least two same-color squares running diagonally from one side of the board to the other. Diagonals are named by the coordinates of their start and end squares : a1-h8 and a8-h1 denote the longest diagonals on the board.
Both the Queen and the Bishop move on diagonals. Unless they are in one of the four corners, they have the choice between a long diagonal and a short diagonal.
