createCanvas(150, 100, WEBGL);

    smooth();

}

​

function draw() {

    background(200);

    fill(250);

    beginShape();

    var t = millis() * 0.001;

    for(var a=0, i=0; a<TWO_PI; a+=TWO_PI/18, i=(i+1)%2) {  

        var r = 20 + 30 * i;

      vertex(r * cos(a+t), r * sin(a+t));

    }

    endShape(CLOSE);

}