.collapsible {
  border-radius: 10px;
  border: double;
  text-align: center;
  outline: none;
}

.active, .collapsible:hover {
  background-color: #ccc;
}

.content {
  padding: 0 18px;
  display: none;
  overflow: hidden;
  background-color: #f1f1f1;
}