Hi, This website is fantastic, really helpful. The only query I have is with one of the quiz questions in level one. The question is: How long is a line from 1,4 to 4,4? The options are: - Can't easily tell from those coordinates, - 4 units, - 3 units. I would have said 3 units but the answer is apparently 4 units? I've tried plotting those two coordinates and keep getting 3. Is this an error or can someone explain how you get 4 units please? Thank you :)