​

let extraCanvas;

​

function setup() {

  createCanvas(400, 400);

​

  extraCanvas = createGraphics(400, 400);

  extraCanvas.clear();

​

}

​

function draw() {

  background(0); //是为了maincanvas

​

  //extraCanvas

  y = random(400);

  z = random(400);

  extraCanvas.fill(255, 0, 0);

  extraCanvas.ellipse(y, z, 5, 5);

  image(extraCanvas, 0, 0);

​

  //main canvas

​

  fill(255, 200, 0);

  let x;

  x = random(20, 50);

  ellipse(200, 200, x);

}

​