Special Moves

The king moves two squares toward a rook, and that rook jumps to the other side. Kingside is the short side (O-O), queenside is the long side (O-O-O). Legal only if the king and that rook haven't moved yet, nothing sits between them, and the king isn't in / doesn't pass through check. Why bother? The king is safer tucked in the corner, and your rook joins the game.

When an enemy pawn moves two squares from its start and lands next to your pawn, you can capture it as if it only moved one — but ONLY on the very next move. Miss the window and it's gone.

A pawn that reaches the far rank turns into a queen, rook, bishop, or knight — your choice. Almost always queen. This is why endgame pawns matter so much.