ECO E10. A chess opening with 3 known variations.
Every line in this family begins 1. d4 Nf6 2. c4 e6 3. Nf3 c5 4. d5 b5, then branches. Each variation below has its own page with the full move order, the position it reaches, and a Stockfish evaluation.
All 5 lines can be practised free in the browser: pick a variation, walk it move by move in Learn mode, then drill it from memory until you can play it without prompting.
The Blumenfeld Countergambit begins 1. d4 Nf6 2. c4 e6 3. Nf3 c5 4. d5 b5. From there it branches into 5 named variations, each with its own move order and typical plans.
The Blumenfeld Countergambit is catalogued under ECO code E10. Individual variations list their own specific code on their page.
Open any variation on Chess Ramp and use Learn mode to walk the line one move at a time, then Drill mode to replay it from memory. Practice runs in your browser with no account required.