Detailed description
5 by 5 grid. Bottom left vertex labelled Y and top right vertex labelled W. A point 3 units right and 2 units up from Y is labelled X. There is a line from the top left of the grid to the bottom right passing through X. The section of the grid with opposite vertices Y and X is coloured red and the section of the grid with opposite vertices X and W is also coloured red.
