label.level1 {
  margin-left: 2em;
}

label.level2 {
  margin-left: 4em;
}

label.level3 {
  margin-left: 6em;
}

:checked + label {
  font-weight: bold;
}

.panel-heading span {
  margin-top: -17px;
  font-size: 15px;
}