[%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.
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 