The system for opening andor closing an inlet valve andor an outlet valve of a liquid container, particularly for water toilets, water tanks or the like, comprises an inlet tube with an inlet valve in the upper portion of the container and an outlet tube with an outlet valve in the bottom portion of the container, both valves being provided with a valve body. A first region of the retainer element is rotatably secured to the backrest and a second region of the retainer element is rotatably secured to a slide that is mounted so as to be displaceable in a rail of the flap element and that can be fixed relative to the rail by a securing element. In a projector headlamp of the invention, a vertical section passing through the center of a projection lens includes a convex front surface and a flat rear surface. The game may also involve non-alternating moves.