function setup(){

    createCanvas(400, 400);

​

}

function draw(){

    background(0,0,0);

    push();

      translate(width/2,height/2);

      fill(0,100,0);

      ellipse(0,0,50,50);

      rotate(angle);

      push();

        // move the origin to the pivot point

        translate(150, 20); 

        // then rotate the grid around the pivot point by a

        // number of degrees equal to the frame count of the sketch

        rotate(angle);

        fill(256,0,0);

        rect(0, 0, 100, 100);

​

    // and draw the square at the origin

}