.collapsible {
  background-color: #777;
  color: white;
  cursor: pointer;
  padding: 18px;
  width: 50%;
  border: 2;
  text-align: left;
  outline: 1;
  font-size: 15px;
  align: centre;
}

.active, .collapsible:hover {
  background-color: #555;
}

.collapsible:after {
  content: '\002B';
  color: white;
  font-weight: bold;
  float: right;
  margin-left: 20px;
}

.active:after {
  content: "\2212";
}

.content {
  padding: 0 18px;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.2s ease-out;
  background-color: #f1f1f1;
}