While this is true, the author actually uses simple arcs on the path for the rounded corners (most Bezier interfaces are implemented in a path that also support

While this is true, the author actually uses simple arcs on the path for the rounded corners (most Bezier interfaces are implemented in a path that also supports simple lines and arcs). In fact, there's only 1 Bezier in the path from the article, the wavy line in the very last image. See the addCurveToPoint and addQuadCurveToPoint methods for drawing cubic and quadratic Bezier curves