3rd Kyū

Regarding bishop maneuvering, it's helpful to first consider which diagonal and anti-diagonal a bishop can control when placed on a specific square.

For an explanation of diagonals and anti-diagonals, please refer to the Diagonal Quiz tutorial.

Let's start by thinking about the diagonals that run from bottom-left to top-right.

The starting point of a diagonal is always a square on the a-file or the 1st rank.

This is because file and rank values change by 1 simultaneously along a diagonal, so tracing down-left (↙) will always reach one board edge before the other.

Let's think in terms of numeric file values (a=1, b=2, ..., h=8).

When the file value is less than the rank value, tracing down-left (↙) hits the a-file (left edge) first.

For example, consider a bishop on d7. The file value is 4 and the rank is 7.

The maximum steps down-left is "file value - 1" = 3. Subtracting 3 from the rank gives 7 - 3 = 4, so the starting point is a4.