Neighbours: g and f

King f1, rook g1 — another pure swap, this time on the kingside. After kingside castling the king will stand on g1, the rook on f1: exactly the squares they occupy now, but the other way round. Minimal movement, maximal effect — my style. Anyone who starts moving the pieces one at a time here has missed the point: castling is one move. King — onto the rook g1.