Single line dual-free Proca retractor with logical play
Theme: Black is in retro-stalemate. The main plan enables two retractions for Black, one of which is a refutation whereas the other one allows White to fulfill the stipulation. Thus, White needs a foreplan to illegalize the refutation move while leaving again Black in retro-stalemate.
Mainplan: -1.Sg5-h7? -1…Rh7-g7 -2.Bg4-h5 and 1.Rxh7# but -1…Bh7-g8!
Solution: -1.Rc8-b8 Rb8-a8 -2.Kc2xRd2 Rd1-d2+ -3.Kb3-c2 Ra8-b8+ -4.Kc2xPb3 b4-b3+ -5.Kc1-c2 Rd2-d1+ -6.Rb8-c8 b5-b4 -7.Bg4-h5 b7-b5 [-7…b6-b5 -8.Bh5-g4 b7-b6 -9.Sg5-h7 Rh7-g7 -10.Bg4-h5 and 1.Rxh7#] -8.Kc2-c1 Rd1-d2+ -9.Kb1-c2 Rd2-d1+ -10.Bh5-g4 Rc2-d2 -11.Kc1-b1 Rd2-c2+ legal position, and now the main plan works: -12.Sg5-h7 Rh7-g7 (now -12…Bh7-g8 is illegal) -13.Bg4-h5 and 1.Rxh7#
