Colle System: Rhamphorhynchus Variation is a chess opening with the ECO code A04, part of the Colle System family. It goes 1. Nf3 c5 2. e3 g6 3. d4 Bg7 4. dxc5 Qa5+. White opens with 1. Nf3 (the Zukertort/Réti knight move) and Black answers 1... c5. After 8 moves it is White to move. After the last move White is a pawn ahead in material. The lesson on the board explains every move of the line and lets you play it yourself; it is free.
The moves
1. Nf3 – White plays the knight to f3
1... c5 – Black plays the pawn to c5
2. e3 – White plays the pawn to e3
2... g6 – Black plays the pawn to g6
3. d4 – White plays the pawn to d4
3... Bg7 – Black plays the bishop to g7
4. dxc5 – White captures on c5 with the d-pawn
4... Qa5+ – Black plays the queen to a5, giving check
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