How to draw a circle with given X and Y coordinates as the middle spot of the circle?
The fillOval fits an oval inside a rectangle, with width=r, height = r you get a circle. If you want fillOval(x,y,r,r) to draw a circle with the center at (x,y) you will have to displace the rectangle by half its width and half its height. This will draw a circle with center at x,y