In 1961, V. R. Parton invented this game, or, to be more precise, these games. In the first game, according to Parton, the black king disappeared because he was fed up always being mated in problems. In both variants, only one king is on the board; the other player must mate within a certain number of moves or lose.
The game is played on a chessboard with almost the normal opening setup: only the black king is now replaced by a second black queen.
White and black should agree on a certain number of moves. When black mates white within that number of moves, he wins the game, otherwise he loses. Draws are not possible.
One can use different mechanics to choose the number of moves. When having some experience with the game, there might be a number acceptable for both players. Otherwise, one can play two games with the same number, changing colors between the games. Another option is to start with a `betting sequence': one player mentions a number, which is his bet how many moves he would need to mate when he would have black. The other player can accept the bet, in which case he plays with white and the player making the bet must mate in the number of moves he has betted, or the other player can make a bet which is a smaller number. In the latter case, the first player has the same choices: accept the bet, or bet again a smaller number. Alternatively, players can write down secretly a number; the player with the smallest number plays with black and must mate in the number he wrote; a coin is tossed when the numbers are equal.
In this Unirexal chessgame, black has twenty knights. The number of moves is prescribed in this game: black must mate in 50 moves. The precise opening setup is as follows:
Black wins the game if he mates white on or before his 50th move, otherwise he loses the game. (Of course, one can also use a betting phase like described above, instead of the 50 moves rule.)