Try thinking of a lethal bridge game where all the floors are made of molten rock. To leap from one glass to another, one must first choose which glass to jump from. Depending on the use, the glass may be either genuine or tempered. You'll have to work this out for yourself and see what your luck is. To stay alive in the game, you must memorize the pane you will be leaping. If you land on a random piece of glass, you can tell if it is actual glass or glass.