Number of possible players:
KBlackBox is a nice logical game, inspired by the emacs blackbox game. A major part of this help file is based on the original emacs help.
KBlackBox is a game of hide and seek played on a grid of boxes. The computer has hidden several balls within this box. By shooting beams into the box and observing where they emerge it is possible to deduce the positions of the hidden balls.
The fewer beams you use and the quicker you are to find the balls, the better (the lower) your score.