-Front ends may wish to use this as a cue to proactively offer the
-option of starting a new game. Therefore, back ends should consider
-returning \cw{TRUE} in situations where the game is \e{lost} as well
-as won, if losing makes it unlikely that the player would play on.
+The return value should be +1 if the game has been successfully
+solved. If the game has been lost in a situation where further play is
+unlikely, the return value should be -1. If neither is true (so play
+is still ongoing), return zero.
+
+Front ends may wish to use a non-zero status as a cue to proactively
+offer the option of starting a new game. Therefore, back ends should
+not return -1 if the game has been \e{technically} lost but undoing
+and continuing is still a realistic possibility.