Queen's Gambit Declined (and Black vs 1.d4, 1.c4, 1.Nf3): Key Ideas

You play Black (ECO D30–D69, D00–D05, A40–A48, A04–A09, A10–A15, E01–E09). 40 lines in 7 chapters, 17 of them core. The course page sets out the plans, the key ideas on their boards, and every chapter.

Learn shows each move with an arrow and the reason for it, then asks for the line from memory; learned lines come back for review after 1, 3, 7, 14, 30, 60, and 120 days. Spar has the opponent choose a random reply at every branch, so each run is a different line. Learn the core lines first.