/* ===== CSS Variables ===== */
:root {
  --primary-color: #3b82f6;
  --secondary-color: #8b5cf6;
  --accent-color: #06b6d4;
  --success-color: #10b981;
  --warning-color: #f59e0b;
  --danger-color: #ef4444;

  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-tertiary: #334155;
  --bg-card: #1e293b;

  --text-primary: #f1f5f9;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;

  --border-color: #475569;
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5);

  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
}

/* ===== Base Styles ===== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  overflow-x: hidden;
}

.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 20px;
}

/* ===== Header ===== */
.header {
  background: linear-gradient(135deg, #1e3a5f 0%, #0f172a 100%);
  padding: 2rem 0;
  border-bottom: 1px solid var(--border-color);
  box-shadow: var(--shadow-md);
}

.title {
  font-size: 2.5rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 0.5rem;
}

.subtitle {
  color: var(--text-secondary);
  font-size: 1.1rem;
}

/* ===== Navigation Tabs ===== */
.nav-tabs {
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--shadow-sm);
}

.nav-tabs .container {
  display: flex;
  gap: 0.5rem;
  overflow-x: auto;
  padding: 1rem 20px;
  scrollbar-width: thin;
  scrollbar-color: var(--border-color) var(--bg-secondary);
}

.tab-btn {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 500;
  transition: all 0.2s ease;
  white-space: nowrap;
  position: relative;
}

.tab-btn:hover {
  background: var(--bg-tertiary);
  color: var(--text-primary);
}

.tab-btn.active {
  background: var(--primary-color);
  color: white;
}

.tab-btn.active::after {
  content: '';
  position: absolute;
  bottom: -17px;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--primary-color);
  border-radius: 3px 3px 0 0;
}

/* ===== Main Content ===== */
.main-content {
  padding: 2rem 0;
  min-height: calc(100vh - 200px);
}

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
  animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ===== Overview Grid ===== */
.overview-grid {
  display: grid;
  gap: 2rem;
}

.theory-panel {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  padding: 2rem;
  box-shadow: var(--shadow-md);
}

.theory-panel h2 {
  color: var(--primary-color);
  margin-bottom: 1.5rem;
  font-size: 1.8rem;
}

.formula-card {
  background: var(--bg-tertiary);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  border-left: 4px solid var(--accent-color);
}

.formula-card h3 {
  color: var(--accent-color);
  margin-bottom: 1rem;
  font-size: 1.2rem;
}

.formula-text {
  font-style: italic;
  color: var(--text-secondary);
  line-height: 1.8;
}

.formula-math {
  font-family: 'Times New Roman', serif;
  font-size: 1.3rem;
  color: var(--text-primary);
  text-align: center;
  padding: 1rem;
  background: var(--bg-secondary);
  border-radius: var(--radius-sm);
  margin: 1rem 0;
}

.formula-desc {
  color: var(--text-muted);
  font-size: 0.95rem;
}

/* ===== Comparison Table ===== */
.comparison-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 1rem;
  font-size: 0.9rem;
}

.comparison-table th,
.comparison-table td {
  padding: 0.75rem 0.5rem;
  text-align: left;
  border-bottom: 1px solid var(--border-color);
}

.comparison-table th {
  background: var(--bg-tertiary);
  color: var(--accent-color);
  font-weight: 600;
  position: sticky;
  top: 0;
}

.comparison-table tbody tr:hover {
  background: var(--bg-tertiary);
}

.comparison-table .row-theory {
  background: rgba(139, 92, 246, 0.1);
}

.comparison-table .row-bridge {
  background: rgba(59, 130, 246, 0.15);
}

.comparison-table .row-practical {
  background: rgba(16, 185, 129, 0.15);
}

/* ===== Twiddle Factor Visualization ===== */
.twiddle-visualization {
  width: 100%;
  height: 200px;
  background: var(--bg-secondary);
  border-radius: var(--radius-md);
  margin: 1rem 0;
}

.twiddle-properties {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.property {
  background: var(--bg-secondary);
  padding: 0.75rem;
  border-radius: var(--radius-sm);
  text-align: center;
}

.property .formula {
  display: block;
  font-family: 'Times New Roman', serif;
  font-size: 1.1rem;
  color: var(--accent-color);
  margin-bottom: 0.25rem;
}

/* ===== Two Panel Layout ===== */
.two-panel-layout {
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 2rem;
  align-items: start;
}

@media (max-width: 1024px) {
  .two-panel-layout {
    grid-template-columns: 1fr;
  }
}

.control-panel,
.visualization-panel {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow-md);
}

.control-panel h2,
.visualization-panel h3 {
  color: var(--primary-color);
  margin-bottom: 0.75rem;
}

.panel-desc {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 1.5rem;
}

/* ===== Controls ===== */
.control-group {
  margin-bottom: 1.25rem;
}

.control-group label {
  display: block;
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 0.5rem;
  font-weight: 500;
}

.control-select,
.control-slider {
  width: 100%;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 0.6rem;
  color: var(--text-primary);
  font-size: 0.95rem;
}

.control-select:focus {
  outline: none;
  border-color: var(--primary-color);
}

.control-slider {
  -webkit-appearance: none;
  height: 6px;
  padding: 0;
}

.control-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 18px;
  height: 18px;
  background: var(--primary-color);
  border-radius: 50%;
  cursor: pointer;
}

.control-slider::-moz-range-thumb {
  width: 18px;
  height: 18px;
  background: var(--primary-color);
  border-radius: 50%;
  cursor: pointer;
  border: none;
}

/* ===== Buttons ===== */
.btn-primary,
.btn-secondary {
  padding: 0.75rem 1.5rem;
  border: none;
  border-radius: var(--radius-md);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  width: 100%;
  margin-bottom: 0.5rem;
}

.btn-primary {
  background: var(--primary-color);
  color: white;
}

.btn-primary:hover {
  background: #2563eb;
  transform: translateY(-1px);
}

.btn-secondary {
  background: var(--bg-tertiary);
  color: var(--text-primary);
}

.btn-secondary:hover {
  background: var(--border-color);
}

/* ===== Formula Display ===== */
.formula-display {
  background: var(--bg-tertiary);
  border-radius: var(--radius-md);
  padding: 1rem;
  margin-top: 1.5rem;
}

.formula-display h4 {
  color: var(--accent-color);
  margin-bottom: 0.75rem;
  font-size: 1rem;
}

/* ===== Chart Containers ===== */
.visualization-panel {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.chart-container {
  background: var(--bg-secondary);
  border-radius: var(--radius-md);
  padding: 1rem;
}

.chart-container.large {
  min-height: 400px;
}

.chart-container h3 {
  color: var(--text-secondary);
  font-size: 1rem;
  margin-bottom: 0.75rem;
}

.chart-container canvas {
  width: 100%;
  height: 250px;
  display: block;
}

.chart-container.large canvas {
  height: 350px;
}

/* ===== Coefficient Display ===== */
.coefficient-display {
  max-height: 150px;
  overflow-y: auto;
  background: var(--bg-secondary);
  border-radius: var(--radius-sm);
  padding: 0.75rem;
  font-family: monospace;
  font-size: 0.85rem;
  color: var(--accent-color);
}

/* ===== Bit Reversal Table ===== */
.bit-reversal-info {
  margin-top: 1.5rem;
  background: var(--bg-tertiary);
  border-radius: var(--radius-md);
  padding: 1rem;
}

.bit-reversal-info h4 {
  color: var(--accent-color);
  margin-bottom: 0.75rem;
}

.bit-reversal-table {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(100px, 1fr));
  gap: 0.5rem;
}

.bit-reversal-item {
  background: var(--bg-secondary);
  padding: 0.5rem;
  border-radius: var(--radius-sm);
  text-align: center;
  font-family: monospace;
  font-size: 0.9rem;
}

/* ===== Stage Indicator & Operation Log ===== */
.stage-info {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}

.stage-indicator {
  background: var(--bg-tertiary);
  border-radius: var(--radius-md);
  padding: 1rem;
}

.operation-log {
  background: var(--bg-tertiary);
  border-radius: var(--radius-md);
  padding: 1rem;
  max-height: 200px;
  overflow-y: auto;
  font-family: monospace;
  font-size: 0.85rem;
}

/* ===== Complexity Table ===== */
.complexity-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.85rem;
}

.complexity-table th,
.complexity-table td {
  padding: 0.5rem;
  text-align: center;
  border-bottom: 1px solid var(--border-color);
}

.complexity-table th {
  background: var(--bg-secondary);
  color: var(--accent-color);
}

/* ===== Twiddle Display ===== */
.twiddle-display {
  background: var(--bg-secondary);
  border-radius: var(--radius-sm);
  padding: 0.75rem;
  margin-top: 0.75rem;
  text-align: center;
  font-family: monospace;
  color: var(--accent-color);
}

/* ===== Audio Info ===== */
.audio-info {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
}

.info-item {
  background: var(--bg-tertiary);
  border-radius: var(--radius-md);
  padding: 1rem;
  text-align: center;
}

.info-item span:first-child {
  display: block;
  color: var(--text-muted);
  font-size: 0.85rem;
  margin-bottom: 0.25rem;
}

.info-item span:last-child {
  color: var(--accent-color);
  font-size: 1.2rem;
  font-weight: 600;
  font-family: monospace;
}

/* ===== Applications Grid ===== */
.applications-grid {
  padding: 1rem;
}

.applications-grid h2 {
  color: var(--primary-color);
  margin-bottom: 2rem;
  font-size: 1.8rem;
  text-align: center;
}

.application-cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.5rem;
}

.app-card {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow-md);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
  border-top: 3px solid var(--primary-color);
}

.app-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.app-icon {
  font-size: 2.5rem;
  margin-bottom: 1rem;
}

.app-card h3 {
  color: var(--text-primary);
  margin-bottom: 0.75rem;
  font-size: 1.1rem;
}

.app-card p {
  color: var(--text-secondary);
  font-size: 0.9rem;
  line-height: 1.6;
  margin-bottom: 1rem;
}

.app-importance {
  color: var(--success-color);
  font-weight: 600;
  font-size: 0.9rem;
}

/* ===== File Input ===== */
.file-input-group {
  margin-top: 1rem;
}

.file-input-group input {
  width: 100%;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 0.75rem;
  color: var(--text-primary);
}

/* ===== Footer ===== */
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 2rem 0;
  margin-top: 3rem;
  text-align: center;
}

.footer p {
  color: var(--text-muted);
  font-style: italic;
}

/* ===== Scrollbar ===== */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-secondary);
}

::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--primary-color);
}

/* ===== Canvas Responsive ===== */
canvas {
  max-width: 100%;
  height: auto;
}

/* ===== Animations ===== */
@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

.pulse {
  animation: pulse 2s infinite;
}

/* ===== Loading State ===== */
.loading {
  display: inline-block;
  width: 20px;
  height: 20px;
  border: 2px solid var(--border-color);
  border-top-color: var(--primary-color);
  border-radius: 50%;
  animation: spin 1s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}