As long as we're talking about hard games, let's pick a level from what may be the hardest game of all time. Jack Shepherd, our community manager, writes, "Why was this level so awesome? It perfectly encapsulated my favorite thing about the classic platform games of my youth — forcing you to memorize intricate sequences of moves until you had the whole thing down so perfect you could play it with your eyes closed. This level moved so fast, that was the only way to do it. Getting it done was just as rewarding as figuring it out was frustrating, which is to say, infinitely."
Also, special mention for the music here.