KBlackBox is a superb :-) graphical logical game, inspired by emacs' blackbox. Copying policy is GPL. Major part of this help file is based on the original emacs's help.
KBlackBox is a game of hide and seek played on an grid of boxes. Your opponent (Random number generator, in this case) has hidden several balls within this box. By shooting rays into the box and observing where they emerge it is possible to deduce the positions of the hidden balls. The fewer rays you use to find the balls, the lower your score.