body {
  background-color: #ffffff;
  font: 1rem/1.4 -apple-system, BlinkMacSystemFont,
    Segoe UI, Roboto, Oxygen,
    Ubuntu, Cantarell, Fira Sans,
    Droid Sans, Helvetica Neue, sans-serif;
}

header {
  position: relative;
  z-index: 2;
  left: 0px;
  text-align: left;
  /*max-width: 420px;*/
  padding: 0.5em;
  background-color: rgba(255, 255, 255, 0.90);
  margin-bottom: 0.5em;
  border-radius: 2px;
}

details summary {
  font-size: 1.0em;
  font-weight: bold;
}

details[open] summary {
  font-size: 1.4em;
  font-weight: bold;
}

header h1 {
  margin-top: 0px;
}

.back {
  float: right;
  text-decoration: none;
}

.back:hover {
  text-decoration: underline;
}

.back::before {
  display: inline-block;
  content: attr(data-index) '<';
  font-weight: bold;
  white-space: nowrap;
  margin-right: 0.2em;
  margin-left: 0.2em;
}

/* ---------- Useful Button styling ---------- */

.ui_buttons {
  width: min-content;
  position: relative;
  background-color: #2699ab;
  border-radius: 1em;
  font-size: 16px;
  color: white;
  margin: 1em 1em 1em 1em;
  padding: 0.8em 1.8em;
  cursor:pointer;
  user-select:none;
  text-align: center;
  text-decoration: none;
  cursor: pointer;
  transition-duration: 0.4s;
  -webkit-transition-duration: 0.4s; /* Safari */
}

.ui_buttons:hover {
  transition-duration: 0.1s;
  background-color: #228999;
}

.ui_buttons:after {
  content: "";
  display: block;
  position: absolute;
  border-radius: 4em;
  left: 0;
  top:0;
  width: 100%;
  height: 100%;
  opacity: 0;
  transition: all 0.5s;
  box-shadow: 0 0 10px 40px white;
}

.ui_buttons:active:after {
  box-shadow: 0 0 0 0 white;
  position: absolute;
  border-radius: 4em;
  left: 0;
  top:0;
  opacity: 1;
  transition: 0s;
}

.ui_buttons:active {
  top: 1px;
}