Dark square strategy
Correspondence games--games in which you have a day or more to make a move--are great learning experiences because they allow you to try out new ideas that you might be hesitant to experiment with in a more demanding time control. In the following game, I tried out a Sicilian line in which black seeks to achieve dark square domination. Notice in the following game how difficult it is for white to make progress due to black's control of the central dark squares. After move 14, black has two pawns and 3 pieces bearing down in e4 and a pawn and a piece attacking f4. Black has achieved equality and has an easier position to play. White logically played f4 to liberate his position, but misplayed the break and then allowed his queen to be trapped, after which there was no hope. Most players on my level probably don't understand color complex strategy, which makes it that much more effective.