@media (max-width: 760px) {
  .site-header .theme-toggle {
    box-sizing: border-box;
    display: flex;
    width: 40px;
    min-width: 40px;
    height: 40px;
    padding: 0;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    line-height: 1;
    text-align: center;
  }

  .site-header .theme-toggle b {
    display: block;
    margin: 0;
    font-size: 17px;
    line-height: 1;
    transform: none;
    vertical-align: 0;
  }
}