Well, well, dear Mr. martyhr! Thank you for your deep attention for our tour.
Really, if you press the minus button until the numbers become negative, the picture will be reverse. But if pressed the plus button the normal view will be restored.
It is not difficult to restrict this function, but I know children who like play by this way.
There are more than two thousands pictures of world treasures in full excursion. So I'm hope that you'll have a good time during their investigation.