int x = 0;
int y = 0;
int r = 50;
int h = 500;
int w = 500;
void setup()
{
background(122,122,122);
size(h,w); 
x = w/2;
y = h/2;
}

void draw()
{
background(122,122,122);
ellipse(x,y,r,r);
}

void keyPressed() {
    if (keyCode == LEFT) r = r +10;
      
    if (keyCode == RIGHT) r = r - 10;
     
}