The difference is subtle, but there’s still a perceptible type of “corner” where the square meets the circle. So if you round a sharp 90 degree angle with a cir

The difference is subtle, but there’s still a perceptible type of “corner” where the square meets the circle. So if you round a sharp 90 degree angle with a circle, you end up with two very subtle corners on either side of the circle, where the circle touches the flat edges. A larger radius doesn’t fix this, it’s inherent to the connection between a square and a circle. One way to think about it is in terms of the derivative of the path (which is what “Gn” means). A straight edge has a constant straight derivative, parallel to the path. A circle has a constant derivative perpendicular to the path. When you connect the two, there is a discontinuity in the derivative, the rate of change of the path jerks suddenly from circle to straight edge. And you can see it visually, even though it’s pretty subtle. With a smoother curve, the derivative is also smooth, and then there’s no abruptness in the curvature where the two edges meet.