summary {
  font-weight:bold;
  cursor: pointer;
  list-style-image: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/85188/arrow-right.svg);
}
summary::-webkit-details-marker {
  background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/85188/arrow-right.svg) no-repeat center/6px;
  color: transparent;
}
details {
  margin: 14px;
  padding: 10px;
}
details[open] {
  background: #eee;
}