Black Box is a ray tracing puzzle game. One player places four or five marbles into a hidden grid. The other player fires light beams into the "black box". The light is deflected, reflected, or absorbed as it passes near or hits the marbles. By observing the reaction of the light beams as they hit, reflect, or deflect, the location of the hidden marbles can eventually be determined. The two players take turns, first hiding then seeking the marbles. The winner is the player who accurately finds the marbles using the least number of light beams.