The theme is HG gives checkmate or stalemate, selfmate, helpmate, doublestalemate, helpselfmate, semireflexmate etc. -- or simply plays a move, as in a proof game, A-to-B-chess, a retro, a study, a chessmathematical composition... …with the ONLY condition being that HG must be prominent in the solution.
Mainplan: -1.b4-b5 ~ -2.b5-b6 & 1.Bc7# but -1…b5xXc4!
A foreplan doubling the HG theme is needed:
Solution: -1.H5xPG6 ~ -2.H4xPG5 ~ -3.b4-b5 ~ (now -3… b5xXc4 is illegal) -4.b5-b6 & 1.Bc7#
Try: -1.H4xPG5? but -1…H6xRG5!
