:root {
  --bg: #f0f4f8;
  --panel: #ffffff;
  --text: #1d2939;
  --muted: #475467;
  --accent: #0f766e;
  --accent-strong: #0b5b55;
  --line: #cbd5e1;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  color: var(--text);
  background: radial-gradient(circle at 15% 10%, #d8f3dc 0%, var(--bg) 48%, #e2e8f0 100%);
}

.app {
  max-width: 1200px;
  margin: 0 auto;
  padding: 1rem;
}

header {
  background: linear-gradient(90deg, #134e4a, #0f766e);
  color: #fff;
  border-radius: 12px;
  padding: 1rem 1.25rem;
  margin-bottom: 1rem;
}

header h1 {
  margin: 0;
  font-size: 1.4rem;
}

header p {
  margin: 0.4rem 0 0;
  color: #d1fae5;
}

.controls {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 0.8rem;
  display: grid;
  gap: 0.8rem;
}

.control-group {
  display: grid;
  gap: 0.4rem;
}

.control-group.inline {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
}

.control-group span {
  font-weight: 600;
  color: var(--muted);
}

input,
select,
button {
  border: 1px solid #94a3b8;
  border-radius: 8px;
  padding: 0.45rem 0.6rem;
  font-size: 0.95rem;
}

button {
  border: 0;
  background: var(--accent);
  color: #fff;
  cursor: pointer;
  transition: background 140ms ease;
}

button:hover {
  background: var(--accent-strong);
}

.status-row {
  margin: 0.9rem 0;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 0.7rem 0.9rem;
}

.status-row p {
  margin: 0.3rem 0;
}

#complexity {
  color: #334155;
}

.canvas-wrap {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 12px;
  min-height: 520px;
  overflow: auto;
}

#treeSvg {
  width: 100%;
  height: 520px;
  display: block;
}

svg text {
  user-select: none;
  pointer-events: none;
}

.hidden {
  display: none !important;
}

@media (max-width: 760px) {
  .app {
    padding: 0.7rem;
  }

  #treeSvg {
    height: 460px;
  }
}