body {
  font-family: sans-serif;
  background: #f9f9f9;
  padding: 2rem;
  color: #333;
}

.controls {
  margin-bottom: 1.5rem;
}

label {
  margin-right: 1rem;
}

.tree {
  margin-top: 2rem;
}

.node {
  border: 1px solid #ccc;
  padding: 0.5rem 1rem;
  margin: 0.5rem;
  background-color: #fff;
  border-radius: 0.5rem;
  box-shadow: 2px 2px 4px rgba(0,0,0,0.1);
  position: relative;
}

.children {
  display: flex;
  justify-content: space-around;
  margin-top: 1rem;
}

.line {
  position: absolute;
  height: 20px;
  width: 2px;
  background: #ccc;
  top: -20px;
  left: 50%;
}