The Impossible Letter is an enjoyable yet extremely difficult find the difference game. In this game, you are required to examine a collection of characters and identify the one that doesn't belong. For instance, if there are 4 letters arranged in a 2 by 2 grid and one letter stands out as being different from the rest, your job is to touch that particular letter to advance to the next level. It might seem quite simple at first glance, but just wait until you get to level 50 of this free online game.