In a recent Youtube video, the black player reaches the following position
[White "NN"]
[Black "Chess Simp"]
[FEN "r2r4/ppp2p1k/2n4P/4p3/P3n3/B1P1P2P/P1qPK2P/R6R b - - 0 1"]
1... Rxd2+ 2.Kf3 Rf2+ (2.Kf1 Rxh2 3.Rxh2 Qxh2 {And mate to follow on the second rank.}) (2.Ke1 Rf2 {White cannot stop checkmate on d2.}) 3.Kg4 Qd2 {The queen joins the attack via e3 or d8}
Now, obviously black is completely winning and under normal circumstances has mate in 4. However, due to the constraints of a self-imposed challenge, black is only allowed to move pieces and pawns to dark squares. Nevertheless, the overwhelming material advantage should lead to checkmate soon. I've put what I think are the best continuations for black, but I'm having trouble finding a forced checkmate in the Kf3 line. Any help?