4th Kyū
Guide
Finally, let's consider how to determine the Bishop's legal moves. The Bishop moves diagonally.
A Bishop can move from one square to another only when the file change equals the rank change. Expressed as a formula:
In other words, a move is legal only when the absolute difference in file and rank is equal.
The Bishop has an important characteristic. A Bishop always stays on squares of the same color. A light-squared Bishop can only ever move to light squares, and a dark-squared Bishop can only ever move to dark squares.