* { 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: auto 1fr;
  gap: 1.5rem;
}

@media (max-width: 780px) {
  .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;
}

/* Board */
.board-section {
  background: #1a1a2e;
  border-radius: 12px;
  padding: 0.75rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  box-shadow: 0 4px 20px rgba(0,0,0,0.3);
}

#board {
  display: block;
  border-radius: 8px;
}

.board-status {
  color: #8888aa;
  font-size: 0.85rem;
  margin-top: 0.5rem;
  font-family: 'SF Mono', 'Menlo', monospace;
}

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

.control-buttons {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
  flex-wrap: wrap;
}

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

.btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.btn-primary { background: #1976d2; color: white; }
.btn-primary:hover:not(:disabled) { background: #1565c0; }
.btn-secondary { background: #e0e0e0; color: #333; }
.btn-secondary:hover:not(:disabled) { background: #d0d0d0; }

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

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

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

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

.dist-chart {
  display: flex;
  align-items: flex-end;
  gap: 4px;
  height: 140px;
  padding-bottom: 2.5rem;
  position: relative;
}

.dist-column {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-end;
  height: 100%;
  position: relative;
}

.dist-observed {
  width: 70%;
  background: linear-gradient(180deg, #ffd700, #e6b800);
  border-radius: 3px 3px 0 0;
  transition: height 0.4s ease;
  min-height: 0;
  position: relative;
  z-index: 2;
}

.dist-expected {
  width: 90%;
  background: rgba(25, 118, 210, 0.15);
  border: 1px dashed rgba(25, 118, 210, 0.4);
  border-radius: 3px 3px 0 0;
  position: absolute;
  bottom: 2.5rem;
  transition: height 0.4s ease;
}

.dist-label {
  font-size: 0.7rem;
  color: #999;
  position: absolute;
  bottom: 0.8rem;
  white-space: nowrap;
}

.dist-count {
  font-size: 0.85rem;
  font-weight: 600;
  color: #333;
  position: absolute;
  bottom: 0;
}

.dist-legend {
  display: flex;
  gap: 1.5rem;
  margin-top: 0.5rem;
  font-size: 0.8rem;
  color: #666;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.legend-swatch {
  display: inline-block;
  width: 12px;
  height: 12px;
  border-radius: 2px;
}

.legend-swatch.observed {
  background: linear-gradient(180deg, #ffd700, #e6b800);
}

.legend-swatch.expected {
  background: rgba(25, 118, 210, 0.15);
  border: 1px dashed rgba(25, 118, 210, 0.4);
}

/* Pascal's Triangle */
.pascal-section {
  background: white;
  border-radius: 8px;
  padding: 1rem;
}

.pascal-triangle {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  margin-bottom: 0.75rem;
}

.pascal-row {
  display: flex;
  gap: 4px;
}

.pascal-row span {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 28px;
  height: 26px;
  padding: 0 4px;
  background: #f0f0f0;
  border-radius: 4px;
  font-size: 0.78rem;
  font-weight: 500;
  color: #555;
}

.pascal-row.highlight span {
  background: linear-gradient(180deg, #fff3e0, #ffe0b2);
  color: #e65100;
  font-weight: 700;
  border: 1px solid #ffcc80;
}

.pascal-note {
  font-size: 0.82rem;
  color: #888;
  text-align: center;
  line-height: 1.5;
}

/* 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; }