I was bored one day, staring at a window, and I started imagining a continuous series of diagonals, going across the panes of the window. It reminded me of the path a pool ball would make, if you shot it from one corner at a 45° angle.

• I always start the path in the upper left corner, and travel at a 45° diagonal across the grid.
• If the path hits an edge of the outer rectangle, it bounces off at a 45° angle and continues its travel.
• The path continues in this way until it hits a corner of the outer rectangle (where a corner pocket would be on a pool table).

Here are the paths generated by some of the windows in my house: