body {
  font-family: 'Roboto', Arial, sans-serif;
  background: linear-gradient(120deg, #f0f4f8 0%, #e0e7ef 100%);
  margin: 0;
  min-height: 100vh;
  color: #222;
}

header {
  text-align: center;
  padding: 2rem 1rem 1rem 1rem;
  background: none;
}

header h1 {
  margin: 0;
  font-size: 2.5rem;
  font-weight: 700;
  letter-spacing: 1px;
}

.subtitle {
  color: #555;
  font-size: 1.1rem;
  margin-top: 0.5rem;
}

main {
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 60vh;
  margin-top: 1rem;
}

.card {
  background: #fff;
  border-radius: 18px;
  box-shadow: 0 4px 24px rgba(0,0,0,0.08);
  padding: 2rem 2.5rem 2.5rem 2.5rem;
  min-width: 340px;
  max-width: 900px;
  width: 100%;
  margin-bottom: 2rem;
  position: relative;
  transition: box-shadow 0.2s;
}

.card:hover {
  box-shadow: 0 8px 32px rgba(0,0,0,0.13);
}

.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  align-items: center;
  margin-bottom: 1.5rem;
}

button {
  background: #4f8cff;
  color: #fff;
  border: none;
  border-radius: 6px;
  padding: 0.6rem 1.2rem;
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.2s, box-shadow 0.2s;
  box-shadow: 0 2px 8px rgba(79,140,255,0.08);
}

button:hover {
  background: #2563eb;
  box-shadow: 0 4px 16px rgba(79,140,255,0.13);
}

.toggle-label {
  margin-left: 1rem;
  font-size: 1rem;
  color: #333;
}

.tree-container {
  min-height: 400px;
  margin-top: 1.5rem;
}

#tooltip {
  background: rgba(40, 40, 60, 0.95);
  color: #fff;
  padding: 0.5rem 1rem;
  border-radius: 8px;
  pointer-events: none;
  font-size: 1rem;
  box-shadow: 0 2px 8px rgba(0,0,0,0.18);
  z-index: 10;
  transition: opacity 0.2s;
}

footer {
  text-align: center;
  padding: 1.5rem 0 1rem 0;
  color: #888;
  font-size: 1rem;
  background: none;
}

@media (max-width: 600px) {
  .card {
    padding: 1rem 0.5rem;
    min-width: unset;
  }
  .controls {
    flex-direction: column;
    gap: 0.7rem;
    align-items: stretch;
  }
  .tree-container {
    min-height: 250px;
  }
  header h1 {
    font-size: 1.5rem;
  }
}