flag = 1;
        source.update({ url: 'https://{s}.basemaps.cartocdn.com/dark_all/{z}/{x}/{y}.png' }, false);
      } else {
        flag = 0;
        source.update({ url: 'https://{s}.basemaps.cartocdn.com/light_all/{z}/{x}/{y}.png' }, false);
      }
    });

    const clip = await fetch('./data/china.geojson').then(res => res.json());

    const layer = new mapboxWind.Layer('temp', source, {
      wireframe: false,
      widthSegments: 1,
      heightSegments: 1,
      styleSpec: {
        'fill-color':