/**
* Draw filled circle of radius r, centred on (x, y).
*
* @param x the x-coordinate of the centre of the circle
* @param y the y-coordinate of the centre of the circle
* @param r the radius of the circle
* @throws RuntimeException if the radius of the circle is negative
*/
public static void filledCircle(double x, double y, double r) {
offscreen.fill(ShapeAssist.circle(x, y, r));
draw();
}
