/* 整站变灰滤镜 */
html.gray-mode {
  filter: grayscale(100%);
  -webkit-filter: grayscale(100%); /* 兼容浏览器 */
  -moz-filter: grayscale(100%);
  -ms-filter: grayscale(100%);
  filter: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg'><filter id='grayscale'><feColorMatrix type='matrix' values='0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0 0 0 1 0'/></filter></svg>#grayscale");
  filter: progid:DXImageTransform.Microsoft.BasicImage(grayscale=1);
  transition: filter 0.5s ease; /* 平滑过渡效果 */
}