* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: #f5f5f5;
  color: #333;
  min-height: 100vh;
}

.app-container {
  max-width: 960px;
  margin: 0 auto;
  padding: 1rem;
}

.header {
  text-align: center;
  margin-bottom: 1.5rem;
}

.header h1 {
  font-size: 1.8rem;
  margin-bottom: 0.3rem;
}

.header p {
  color: #666;
  font-size: 0.95rem;
}

.main-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
}

@media (max-width: 700px) {
  .main-content { grid-template-columns: 1fr; }
}

.left-panel, .right-panel {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

h3 {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: #888;
  margin-bottom: 0.75rem;
}

/* Traffic light */
.light-section {
  display: flex;
  justify-content: center;
}

.traffic-light {
  background: #222;
  border-radius: 16px;
  padding: 16px 20px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  box-shadow: 0 4px 20px rgba(0,0,0,0.3);
}

.light {
  width: 80px;
  height: 80px;
  border-radius: 50%;
  transition: box-shadow 0.3s, opacity 0.3s;
  opacity: 0.2;
}

.light.red { background: #d32f2f; }
.light.yellow { background: #f9a825; }
.light.green { background: #388e3c; }

.light.active.red {
  opacity: 1;
  box-shadow: 0 0 30px #d32f2f, 0 0 60px rgba(211,47,47,0.4);
}

.light.active.yellow {
  opacity: 1;
  box-shadow: 0 0 30px #f9a825, 0 0 60px rgba(249,168,37,0.4);
}

.light.active.green {
  opacity: 1;
  box-shadow: 0 0 30px #388e3c, 0 0 60px rgba(56,142,60,0.4);
}

/* Controls */
.controls-section {
  background: white;
  border-radius: 8px;
  padding: 1rem;
}

.transitions-container {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
  flex-wrap: wrap;
}

.trans-btn {
  flex: 1;
  padding: 0.5rem 0.75rem;
  border: 1px solid #ddd;
  border-radius: 6px;
  background: white;
  cursor: pointer;
  font-size: 0.85rem;
  transition: all 0.15s;
  min-width: 70px;
  text-align: center;
}

.trans-btn:hover:not(:disabled) {
  border-color: #1976d2;
  background: #e3f2fd;
}

.trans-btn:disabled {
  opacity: 0.35;
  cursor: not-allowed;
}

.trans-btn.enabled {
  border-color: #1976d2;
  color: #1976d2;
  font-weight: 600;
}

.control-buttons {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 0.5rem;
}

.btn {
  padding: 0.5rem 1rem;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.85rem;
  font-weight: 500;
  transition: background 0.15s;
}

.btn-primary { background: #1976d2; color: white; }
.btn-primary:hover { background: #1565c0; }
.btn-secondary { background: #e0e0e0; color: #333; }
.btn-secondary:hover { background: #d0d0d0; }

.auto-label {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.85rem;
  color: #666;
  margin-top: 0.25rem;
}

.auto-label input[type="range"] {
  flex: 1;
  max-width: 120px;
}

#speed-label {
  min-width: 2.5em;
  text-align: right;
}

/* Event log */
.log-section {
  background: white;
  border-radius: 8px;
  padding: 1rem;
}

.event-log {
  font-family: 'SF Mono', 'Menlo', monospace;
  font-size: 0.8rem;
  max-height: 200px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.log-entry {
  padding: 0.25rem 0.5rem;
  border-radius: 4px;
  background: #f9f9f9;
}

.log-entry.info { color: #888; }
.log-entry.go { color: #388e3c; border-left: 3px solid #388e3c; }
.log-entry.slow { color: #f9a825; border-left: 3px solid #f9a825; }
.log-entry.stop { color: #d32f2f; border-left: 3px solid #d32f2f; }

/* State diagram */
.state-section {
  background: white;
  border-radius: 8px;
  padding: 1rem;
}

.state-diagram {
  display: flex;
  justify-content: center;
}

#petri-svg {
  width: 100%;
  max-width: 300px;
}

/* Explainer */
.explainer-section {
  background: white;
  border-radius: 8px;
  padding: 1rem;
}

.explainer-content {
  font-size: 0.9rem;
  line-height: 1.6;
  color: #555;
}

.explainer-content p { margin-bottom: 0.75rem; }
.explainer-content ul { margin: 0.5rem 0 0.75rem 1.5rem; }
.explainer-content li { margin-bottom: 0.3rem; }