Tomf made a puzzle called Mouse Maze. The basic concept is that it solves mazes with a ridiculously inefficient algorithm, and you have to find input to maximise the inefficiency. It's quite easy to make a maze that takes a few hundred steps, but after that it gets difficult.
For a long time, this very elegant maze was the second highest scoring, at 1135 moves. As it was saved to the folder of shared mazes, lots of people ran it and got the same score, but there was one single person with a higher score of 1223, with an unknown maze. Then recently someone came up with this maze, giving 1364 moves, and saved it, so it was possible for anybody to reach the top of the score table.
When Tomf told me someone had found and shared a better maze I was a little disappointed - I'd liked the mystery of the top solution being unknown. I have now fixed this; see the high score table.