Semi-Slav Defense

Black combines ...c6 and ...e6 for a solid but flexible setup that often turns very sharp.

It is reached after 8 moves: 1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. Nc3 e6.

White is to move and has 35 legal moves. Over the next four moves — two for each side — the game can branch into 1,359,257 different games. Those games reach 433,707 different positions: most positions can be reached in more than one way, 3.1 on average.

The Lichess opening list names 18 further lines after this position, such as Queen's Gambit Declined (5. Bg5 Nbd7 6. e3) and Anti-Moscow Gambit (5. Bg5 h6 6. Bh4).

The same moves can be played in 288 different legal orders that all reach this position. For example 1. c4 d5 2. d4 c6 3. Nf3 Nf6 4. Nc3 e6, which starts as the English Opening.