css transition

#content #nav a:hover {
    color: black;
    background-color: #AD310B;
    /* Firefox */
    -moz-transition: all 1s ease-in;
    /* WebKit */
    -webkit-transition: all 1s ease-in;
    /* Opera */
    -o-transition: all 1s ease-in;
    /* Standard */
    transition: all 1s ease-in;
}

details[open] summary ~ * {
  animation: sweep .5s ease-in-out;
}

@keyframes sweep {
  0%    {opacity: 0; transform: translateX(-10px)}
  100%  {opacity: 1; transform: translateX(0)}
}