prize13-4, Exercise 1: Three rule changes

Model answer (check the details):

1. The queen. She moved from one square diagonally to any distance in a straight or diagonal line. Attacks and mating threats became fast and the game turned tactical.

2. The bishop. It moved from a two-square diagonal leap to any distance along a diagonal, without leaping. Bishops became strong, long-range pieces and the diagonal became a main line of attack.

3. The pawn's first move and promotion. A pawn could advance two squares from its start (with capture in passing, en passant), and a pawn reaching the far side could become a queen. Openings opened up sooner and pawn endgames gained a clear goal.

Others: castling gained fixed rules.

Care: the changes were gradual and regional, and the dating is debated.