text: const {Scene, Path, Sprite, Gradient} = spritejs;
  const container = document.getElementById('stage');
  const scene = new Scene({
    container,
    width: 1200,
    height: 600,
  });
  const layer = scene.layer();
  
  const birdsJsonUrl = 'https://s5.ssl.qhres2.com/static/5f6911b7b91c88da.json';
  const birdsRes = 'https://p.ssl.qhimg.com/d/inn/c886d09f/birds.png';
  
  (async function () {
    await scene.preload([birdsRes, birdsJsonUrl]);
    const d = 'M480,437l-29-26.4c-103-93.4-171-155-171-230.6c0-61.6,48.4-110,110-110c34.8,0,68.2,16.2,90,41.8C501.8,86.2,535.2,70,570,70c61.6,0,110,48.4,110,110c0,75.6-68,137.2-171,230.8L480,437Z';
  
    const gradient = new Gradient({
      vector: [280, 470, 680, 70],
      colors: [{
        offset: 0,
        color: 'rgba(255,0,0,1)',
      }, {
        offset: 0.5,
        color: 'rgba(255,0,0,0)',
      }, {
        offset: 1,
        color: 'rgba(255,0,0,0)',
      }],
    });
  
    const path = new Path({
      d,
      lineWidth: 26,
      fillColor: 'red',
      strokeColor: gradient,
      // lineJoin: 'bevel',
    });
  
    layer.append(path);
    window.path = path;
  
    const bird = new Sprite('bird1.png');
    bird.attr({
      anchor: [0.5, 0.5],
      size: [65, 45],
      offsetPath: d,
      zIndex: 200,
    });
  
    layer.append(bird);
  
    bird.animate([
      {offsetDistance: 0},
      {offsetDistance: 1},
    ], {
      duration: 6000,
      iterations: Infinity,
    });
  
    let i = 0;
    setInterval(() => {
      bird.attributes.texture = `bird${i++ % 3 + 1}.png`;
    }, 100);
  
    const startTime = Date.now();
    const T = 6000;
    requestAnimationFrame(function next() {
      const p = Math.PI * 2 * (Date.now() - startTime) / T;
      const colors = [
        {offset: 0, color: 'rgba(255,0,0,1)'},
        {offset: 0.5 + 0.5 * Math.abs(Math.sin(p)), color: 'rgba(255,0,0,0)'},
        {offset: 1, color: 'rgba(255,0,0,0)'},
      ];
  
      const gradients = new Gradient({
        vector: [280, 470, 680, 70],
        colors,
      });
      path.attr({strokeColor: gradients});
  
      requestAnimationFrame(next);
    });
  }());