createCanvas(400, 400);

}

​

function draw() {

  background(220);

noStroke()

 //background circle

  circle(mouseX,mouseY,200,200)

  let r= map(mouseX,0,width,0,250)

  let g= map(mouseY,0,height,0,250)

  fill(mouseX, mouseY, 0)

  //middle circle

  circle(200,200,200)

 fill (r, g, 0) 

    save("shadow.jpg");

}