Calculation: long lines is lesson 1 of 9 in Real-game tactics 9: Master calculation, a tactics course suited to players rated around 2200 (advanced players). Forcing sequences of four moves or more. Picture the board after every move. 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.
What you practise
White to move and win. (3 positions)
White to move: mate in 4.
Black to move: mate in 4.
Black to move and win. (2 positions)
Worked examples
White to move and win. 1.Rxf6+ gxf6 2.Qh5+ Ke7 3.Rg7+ Kd8 4.Qc5 Qe5 5.Qxf8+. The had to move, and the behind it was lost. You win the rook on f6 and come out 5 points ahead.
White to move: mate in 4. 1.Bxh7 Rxc5 2.Bxc5+ Qd6 3.Qf6+ Kf8 4.Bxd6#. The attack on the king was decisive. Mate in 4.
chessGM