code: function animate(timestamp) {
        if (timestamp === undefined) {
          timestamp = 0;
        }
        let dt = (timestamp - lasttime)/1000;
        lasttime = timestamp;
  
        window.stats.tick();
  
        if (tick) {
          tick(dt);
        }
  
        window.reqID = requestAnimationFrame(animate);
      }
docs: update