// initialise to position of largest circle
circleXPosition = 0 ;
circleYPosition = 0 ;
// set the colour
g.setColor(Color.green) ;
for (diameter = 200 ; diameter > 0 ; diameter -= 20)
{
// draw the circle for this iteration
g.drawOval(circleXPosition,circleYPosition,diameter,diameter) ;
// update the circle position ready for next time
circleXPosition = circleXPosition + 10 ;
circleYPosition = circleYPosition + 10 ;
}