This is an answers video, but it is good enough for purposes of discussion. You can find the full test as well as the "difficult" test here http://www.law-11.com/video-training.html This is a good intro to the flash lag effect. Flash lag is when "A moving object is perceived as spatially leading its real position at an instant defined by a time marker". I was shocked the first time I saw this video. I really had to train my brain to compensate for the flash lag effect.______________ In a perfect world, the "answers video" is mandatory viewing for all parents, coaches, and players. Even in an imperfect world, this should be mandatory viewing for all referees getting their Grade 8 intro to refereeing course. and then re-watched again at some point. I think this video is eye-opening to how difficult offside can be. And if you aren't watching the line, on the line; and are instead looking at the ball... forget about it.