body {
  font-family: Arial;
  background: #f4f4f4;
  padding: 20px;
}

.toolbar {
  margin-bottom: 15px;
}

ul.tree,
ul.tree ul {
  list-style: none;
  margin: 0;
  padding-left: 20px;
  position: relative;
}

ul.tree ul::before {
  content: '';
  position: absolute;
  top: 0;
  left: 10px;
  border-left: 2px solid #ccc;
  height: 100%;
}

ul.tree li {
  margin: 5px 0;
  padding-left: 20px;
  position: relative;
}

ul.tree li::before {
  content: '';
  position: absolute;
  top: 12px;
  left: 0;
  width: 10px;
  border-top: 2px solid #ccc;
}

.node {
  display: inline-block;
  background: white;
  padding: 5px;
  border-radius: 5px;
  border: 1px solid #ddd;
}

.node button {
  margin-left: 5px;
  font-size: 11px;
}

.toggle {
  cursor: pointer;
  font-weight: bold;
  margin-right: 5px;
  color: blue;
}