:root {
  --theme: #85c033;
  --active: #d80c18;
}
img[data-src]{opacity: 0;}
img[done]{opacity: 1;transition: opacity .01s;}
 
html {
  font-size: calc(75vw / 1920 * 100);
}
@media (min-width: 1921px) {
  html {
    font-size: 100px;
  }
}
/* 适配pad: 900~500 */
@media (max-width: 900px) {
  html {
    font-size: calc(900px / 1920 * 100);
  }
}

/* 移动端 */
@media (max-width: 500px) {
  html {
    font-size: calc(100vw / 750 * 100);
  }
}