In the struggle for a place under the sun

Win a place under the sun in the selected business area (if it is to win) is pretty easy. Even more difficult, as evidenced by the practice, keep the gains. Every day come new challengers with new ideas. In principle, it makes a pretty perky move. That, at least, not to lose its positions. And it is better to strengthen.
The owners of the Viennese cafe «Diglas» went unconventional way and decided to capture the imagination of their customers are not culinary delights or exclusive service (and, in fact, what's the surprise). They went, so to speak, on the reverse side of the process. And set in a toilet stall of his institution "secret door". That is, from the outside, while the door is not locked, it remains transparent. The idea, in principle, is good. No need to gently pull the handle, fearing catch forgetful visitor for the most interesting process. However, when the visitor closes inside the booth, on the glass, made of silver halide is energized, its molecules begin to absorb more light, and as a result it becomes translucent. Here's a trick.
In principle, cool and fresh (for lack of other options for raising). It is hoped that power outages in the cafe will not happen. And then, you know, whether noble confusion can happen.