Colle System: Siroccopteryx Variation
ECO A40
Move order
1. d4 g6 2. Nf3 Bg7 3. e3 c5 4. Bd3 cxd4 5. Nxd4 Qa5+
Ideas
ECO A covers irregular and flank openings—systems that skip the main e4/d4 fight early. White builds a pawn center and keeps the position more closed than after 1. e4. 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.