Modern Defense: Semi-Averbakh Variation, Polish Variation
ECO A04
Move order
1. Nf3 c5 2. c4 g6 3. d4 Bg7 4. e4 Qb6
Ideas
ECO A covers irregular and flank openings—systems that skip the main e4/d4 fight early. White develops a knight and keeps flexible transpositions into d4 or c4 setups. This entry tracks a longer branch in the opening tree. Use the diagram and SAN list to recognize the tabiya, then try the line against Maia to explore typical plans in practice.