Complex sentence: A reflexmate is a chess problem in which white, moving first, must force black to deliver checkmate within a specified number of moves against his will-with the added condition that if either player can give checkmate, they must.
Split into simpler sentences: A reflexmate is a chess problem in which white, moving first, must force black to deliver checkmate within a specified number of moves against his will. Moreover, there is added condition that if either player can give checkmate, they must.