1. c1-e3

White created two possibilities to recycle pieces. Black cannot counter them both with one move. If Black plays 1. … d8-d6;x or d1-d6;x, then White will reply with 2. a3-d3 and capture f1. If Black plays any other move but 1. … b6-d6, white will play 2. d1-d6;x and, on top of that, force Black to remove his row on the d1-d8 line. So, Black will normally choose for 1. … b6-d6, leaving White no other option than 2. c1-g3;x or i1-g3;x. Black has the possibility the level the score through 2. … d2;x.