1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. b1c3  3... d7d5  4. g1f3  4... c7c6  5. e2e3  5... b8d7  6. f1d3  6... d5c4  7. d3c4  7... b7b5  8. c4e2 [%c_effect e2;square;e2;type;Interesting;persistent;true] I wouldn't call this move a \"sideline\", but it's much less popular than 8.Bd3. 8... a7a6 Black has many ways to play and I leave the subtleties of move orders to the Semi-Slav experts. Some possibilities: 9. e1g1  9... c6c5 