chessGMMate in two is lesson 6 of 7 in Real-game tactics 1: Free pieces and first tactics, a tactics course suited to players rated around 600 (beginners). Two-move mates: a forcing first move, often a check or a sacrifice, leaves the king without a defence. It has 7 interactive exercises: 7 calculated lines from real positions. You play every move on a board and get feedback straight away. The lesson is free.