The magician shows spectators a glass board where there are placed colour light bulbs and switches. The board is transparent so the spectators can see all connections among the light bulbs and switches. All switches are marked by colour badges. Switches are marked with the same colours as light bulbs which are connected to them at the beginning of the performance. That means that the switch with the green badge lights the green bulb, the red marked switch lights the red bulb and so on. If a spectator interchanges light bulbs or badges, switches should switch on light bulbs of different colours. But not magician! He can anytime set any switches, to light the bulb, which is the same colour as its badge. Even in the case when a switch is marked by several badges. The switch that is not marked by a badge, does not light a bulb. The magician can finish crazy activity of electric circuits (when switches switch on light bulbes which are not connected to them) anytime.