Use full screen. Adjust the location of the square to see the effect of anti-aliasing (I suspect) on a pen size of 1. Since the lines are vertical and horizontal (not curved or diagonal), it could be something else. Maybe just the pen size alone. Watch the width of the lines change. Ideas anyone?
Antialiasing: A technique used to add greater realism to a digital image by smoothing jagged edges on curved lines and diagonals.
