body {
  color:#ffffff;
  font-size:18px;
  padding:5px 25px;
  background:#000000;
}

.inner {
  margin-left:35px;
}

details > summary {
  cursor:pointer;
  list-style-type:none;
}

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

details > summary::before {
  margin-right:5px;
  vertical-align:middle;
  image-rendering:pixelated;
  content:url("assets/folder.png");
}

details[open] > summary::before {
  image-rendering:pixelated;
  content:url("assets/folder_open.png");
}