details {
  margin: 0 auto ;
   background: #c9e1f6;
  margin-bottom: .5rem;
  box-shadow: 0 .1rem 1rem -.5rem rgba(0,0,0,.4);
  border-radius: 5px;
  overflow: hidden;
}

summary {
  padding: 5px !important;
  display: block;
  background: #004494;
  position: relative;
  cursor: pointer;
  user-select: none;
  color: #fff;
  height: auto;
}

summary:before {
content: '';
  border-width: 1rem;
  border-style: solid;
  border-color: transparent transparent transparent #fff;
  margin-top: .3rem;
  transform: rotate(0);
  transform-origin: .2rem 50%;
  transition: .25s transform ease;
  float: right;
}

/* THE MAGIC */
details[open] > summary:before {
  transform: rotate(90deg);
}


details summary::-webkit-details-marker {
  display:none;
}

details > ul {
  margin-bottom: 0;
  background: #c9e1f6;
}