Trading Places: Kingside

King on d1, rook on e1 — neighbours in the very centre of the first rank. Kingside castling will separate them delicately: the king proceeds to g1, the rook shifts just one square, to f1. Observe the economy: minimal movement — maximal benefit, the king sheltered, the rook in play. The hasty beginner moves the king two squares here and lands on e1 — his own rook's square. There is only one correct gesture: king — onto the rook e1.