/* Nuclear Collision Visualization — Dual-track UI */
:root {
  --bg-dark: #0d1117;
  --bg-panel: #161b22;
  --border: #30363d;
  --text: #e6edf3;
  --text-muted: #8b949e;
  --accent: #58a6ff;
  --accent-thermal: #f0883e;
  --expert: #3fb950;
  --beginner: #a371f7;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: 'Segoe UI', system-ui, sans-serif;
  background: var(--bg-dark);
  color: var(--text);
  min-height: 100vh;
}

header {
  padding: 1rem 1.5rem;
  border-bottom: 1px solid var(--border);
  background: var(--bg-panel);
}
header h1 {
  margin: 0 0 0.25rem 0;
  font-size: 1.35rem;
  font-weight: 600;
}
header .subtitle {
  color: var(--text-muted);
  font-size: 0.9rem;
}

.track-tabs {
  display: flex;
  gap: 0;
  padding: 0 1.5rem;
  border-bottom: 1px solid var(--border);
  background: var(--bg-panel);
}
.track-tabs button {
  padding: 0.6rem 1.2rem;
  border: none;
  background: transparent;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 0.95rem;
  border-bottom: 2px solid transparent;
}
.track-tabs button.active {
  color: var(--text);
  border-bottom-color: var(--accent);
}
.track-tabs button[data-track="beginner"].active { border-bottom-color: var(--beginner); }
.track-tabs button[data-track="expert"].active { border-bottom-color: var(--expert); }

main {
  padding: 1rem 1.5rem 2rem;
  max-width: 1200px;
  margin: 0 auto;
}

.explanation-panel {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem 1.25rem;
  margin-bottom: 1.25rem;
}
.explanation-panel h3 { margin-top: 0; font-size: 1.05rem; }
.explanation-panel p { margin: 0.5rem 0; line-height: 1.5; }
.explanation-panel .analogy { color: var(--beginner); font-style: italic; }
.explanation-panel .formula { font-family: ui-monospace, monospace; background: #0d1117; padding: 0.25rem 0.5rem; border-radius: 4px; }

.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 1.5rem;
  margin-bottom: 1.25rem;
  align-items: flex-start;
}
.control-group label {
  display: block;
  margin-bottom: 0.25rem;
  font-size: 0.9rem;
  color: var(--text-muted);
}
.control-group input[type="range"] {
  width: 180px;
  margin-right: 0.5rem;
  accent-color: var(--accent);
}
.control-group .value { font-family: ui-monospace, monospace; font-size: 0.9rem; }

.viz-container {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem;
  margin-bottom: 1rem;
}
.viz-container h3 { margin: 0 0 0.75rem 0; font-size: 1rem; }
#spectrum-chart { width: 100%; min-height: 320px; }
#expansion-viz { width: 100%; height: 200px; }

.takeaway-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}
.takeaway-table th, .takeaway-table td {
  border: 1px solid var(--border);
  padding: 0.5rem 0.75rem;
  text-align: left;
}
.takeaway-table th { background: var(--bg-dark); color: var(--text-muted); }
.takeaway-table .expert-col { color: var(--expert); }
.takeaway-table .beginner-col { color: var(--beginner); }

.validation-badge {
  display: inline-block;
  padding: 0.25rem 0.5rem;
  border-radius: 4px;
  font-size: 0.8rem;
  margin-top: 0.5rem;
}
.validation-badge.valid { background: rgba(63, 185, 80, 0.2); color: var(--expert); }
.validation-badge.invalid { background: rgba(248, 81, 73, 0.2); color: #f85149; }

.hidden { display: none !important; }

footer {
  padding: 1rem 1.5rem;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.85rem;
}