:root {
  --bg-primary: #fafafa;
  --bg-secondary: #ffffff;
  --bg-tertiary: #f0f0f0;
  --text-primary: #0a0a0a;
  --text-secondary: #4a4a4a;
  --text-muted: #8a8a8a;
  --border-color: #e0e0e0;
  --accent: #0a0a0a;
  --accent-light: #2a2a2a;
  --sample-color: rgba(10, 10, 10, 0.6);
  --theoretical-color: #0a0a0a;
}

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

body {
  font-family: 'IBM Plex Sans', -apple-system, BlinkMacSystemFont, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  min-height: 100vh;
}

.app-container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 24px;
}

header {
  margin-bottom: 32px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--border-color);
}

header h1 {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 1.75rem;
  font-weight: 600;
  letter-spacing: -0.5px;
  margin-bottom: 8px;
}

header p {
  color: var(--text-secondary);
  font-size: 0.95rem;
}

.main-grid {
  display: grid;
  grid-template-columns: 360px 1fr;
  gap: 24px;
}

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

.sidebar {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.panel {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  overflow: hidden;
}

.panel-header {
  padding: 14px 18px;
  border-bottom: 1px solid var(--border-color);
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.8rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-secondary);
}

.collapsible-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
  user-select: none;
  transition: background 0.15s ease;
  padding: 19px;
}

.collapsible-header:hover {
  background: var(--bg-tertiary);
}

.collapse-icon {
  font-size: 0.7rem;
  transition: transform 0.2s ease;
  display: inline-block;
}

.collapsible-header.collapsed .collapse-icon {
  transform: rotate(-90deg);
}

.panel-content.collapsed {
  display: none;
}

.panel-content {
  padding: 18px;
}

/* Distribution Selector */
.distribution-categories {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.category-group {
  margin-bottom: 8px;
}

.category-group:last-child {
  margin-bottom: 0;
}

.category-label {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-muted);
  margin-bottom: 8px;
  font-weight: 500;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 6px;
  user-select: none;
  transition: color 0.15s ease;
}

.category-label:hover {
  color: var(--text-secondary);
}

.category-toggle {
  font-size: 0.6rem;
  transition: transform 0.2s ease;
  display: inline-block;
}

.category-label.collapsed .category-toggle {
  transform: rotate(-90deg);
}

.distribution-list {
  display: flex;
  flex-direction: column;
  gap: 4px;
  max-height: 500px;
  overflow: hidden;
  transition: max-height 0.3s ease, opacity 0.2s ease;
}

.distribution-list.collapsed {
  max-height: 0;
  opacity: 0;
  margin: 0;
}

.distribution-btn {
  background: none;
  border: 1px solid transparent;
  padding: 10px 14px;
  text-align: left;
  cursor: pointer;
  border-radius: 6px;
  font-family: 'IBM Plex Sans', sans-serif;
  font-size: 0.9rem;
  color: var(--text-primary);
  transition: all 0.15s ease;
}

.distribution-btn:hover {
  background: var(--bg-tertiary);
}

.distribution-btn.active {
  background: var(--accent);
  color: white;
  border-color: var(--accent);
}

/* Parameters */
.param-group {
  margin-bottom: 18px;
}

.param-group:last-child {
  margin-bottom: 0;
}

.param-label {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
}

.param-name {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.param-value {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.85rem;
  font-weight: 500;
  background: var(--bg-tertiary);
  padding: 2px 8px;
  border-radius: 4px;
}

input[type="range"] {
  width: 100%;
  height: 6px;
  -webkit-appearance: none;
  appearance: none;
  background: var(--bg-tertiary);
  border-radius: 3px;
  outline: none;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 16px;
  height: 16px;
  background: var(--accent);
  border-radius: 50%;
  cursor: pointer;
  transition: transform 0.1s ease;
}

input[type="range"]::-webkit-slider-thumb:hover {
  transform: scale(1.15);
}

input[type="range"]::-moz-range-thumb {
  width: 16px;
  height: 16px;
  background: var(--accent);
  border-radius: 50%;
  cursor: pointer;
  border: none;
}

/* Sampling Controls */
.sample-controls {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.sample-size-selector {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}

.sample-size-btn {
  flex: 1;
  min-width: 60px;
  padding: 8px 12px;
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.8rem;
  cursor: pointer;
  transition: all 0.15s ease;
}

.sample-size-btn:hover {
  border-color: var(--accent);
}

.sample-size-btn.active {
  background: var(--accent);
  color: white;
  border-color: var(--accent);
}

.action-btn {
  width: 100%;
  padding: 12px 16px;
  background: var(--accent);
  color: white;
  border: none;
  border-radius: 6px;
  font-family: 'IBM Plex Sans', sans-serif;
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.15s ease;
}

.action-btn:hover {
  background: var(--accent-light);
}

.action-btn.secondary {
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
}

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

.btn-row {
  display: flex;
  gap: 8px;
}

.btn-row .action-btn {
  flex: 1;
}

/* Main Content */
.main-content {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.chart-container {
  position: relative;
  height: 400px;
  padding: 20px;
}

@media (max-width: 768px) {
  .chart-container {
    height: 300px;
  }
}

/* Statistics Grid */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 12px;
}

.stat-item {
  background: var(--bg-tertiary);
  padding: 14px 16px;
  border-radius: 6px;
}

.stat-label {
  font-size: 0.7rem;
  letter-spacing: 0.5px;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.stat-value {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 1.1rem;
  font-weight: 500;
}

/* Statistics Formulas Section */
.stats-formulas {
  margin-top: 20px;
  padding-top: 16px;
  border-top: 1px solid var(--border-color);
}

.formulas-header {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.75rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-secondary);
  margin-bottom: 12px;
}

.formulas-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.formula-item {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.8rem;
  color: var(--text-secondary);
  display: flex;
  align-items: baseline;
  gap: 8px;
}

.formula-label {
  color: var(--text-primary);
  font-weight: 500;
  min-width: 120px;
}

.formula-value {
  color: var(--text-secondary);
  background: var(--bg-tertiary);
  padding: 3px 8px;
  border-radius: 3px;
}

/* Distribution Info */
.info-content {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.info-section h4 {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.info-section p {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.formula {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.85rem;
  background: var(--bg-tertiary);
  padding: 12px 16px;
  border-radius: 6px;
  overflow-x: auto;
}

.formula-symbols {
  margin-top: 12px;
  padding: 12px 16px;
  background: var(--bg-secondary);
  border-left: 3px solid var(--border-color);
  border-radius: 4px;
}

.symbol-item {
  font-size: 0.8rem;
  color: var(--text-secondary);
  margin-bottom: 6px;
  line-height: 1.5;
}

.symbol-item:last-child {
  margin-bottom: 0;
}

.symbol-item .symbol {
  font-family: 'IBM Plex Mono', monospace;
  font-weight: 600;
  color: var(--text-primary);
  background: var(--bg-tertiary);
  padding: 2px 6px;
  border-radius: 3px;
  margin-right: 4px;
}

.use-cases {
  list-style: none;
}

.use-cases li {
  font-size: 0.85rem;
  color: var(--text-secondary);
  padding: 4px 0;
  padding-left: 16px;
  position: relative;
}

.use-cases li::before {
  content: '→';
  position: absolute;
  left: 0;
  color: var(--text-muted);
}

/* Sample Statistics */
.sample-stats {
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--border-color);
}

.sample-stats-title {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.sample-stats-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 8px;
}

.sample-stat {
  display: flex;
  justify-content: space-between;
  font-size: 0.8rem;
}

.sample-stat-label {
  color: var(--text-muted);
}

.sample-stat-value {
  font-family: 'IBM Plex Mono', monospace;
  font-weight: 500;
}

/* Legend */
.chart-legend {
  display: flex;
  gap: 20px;
  justify-content: center;
  margin-top: 12px;
  margin-bottom: 10px;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.8rem;
  color: var(--text-secondary);
}

.legend-color {
  width: 24px;
  height: 3px;
  border-radius: 2px;
}

.legend-color.theoretical {
  background: var(--theoretical-color);
}

.legend-color.samples {
  background: var(--sample-color);
  height: 12px;
  width: 12px;
  border-radius: 2px;
}

/* Scrollbar */
::-webkit-scrollbar {
  width: 6px;
  height: 6px;
}

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

::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--text-muted);
}

/* Animation */
@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.panel {
  animation: fadeIn 0.3s ease-out;
}

/* CSV Upload Styles */
.csv-upload-controls {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.csv-import-panel {
  overflow: visible;
}

.csv-import-panel .panel-content {
  overflow: visible;
}

.file-upload-label {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 14px 16px;
  background: var(--bg-tertiary);
  border: 2px dashed var(--border-color);
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.file-upload-label:hover {
  border-color: var(--accent);
  background: var(--bg-secondary);
}

.file-upload-icon {
  font-size: 1.1rem;
}

.file-upload-text {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.csv-filename {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.8rem;
  color: var(--text-secondary);
  word-break: break-all;
}

.csv-column-select {
  margin-top: 4px;
}

/* Custom Select Dropdown for CSV Column */
.csv-column-select .custom-select {
  position: relative;
  width: 100%;
}

.csv-column-select .select-trigger {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border-color);
  border-radius: 6px;
  font-size: 0.9rem;
  font-family: 'IBM Plex Sans', sans-serif;
  background: var(--bg-secondary);
  cursor: pointer;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  display: flex;
  justify-content: space-between;
  align-items: center;
  user-select: none;
}

.csv-column-select .select-trigger:hover {
  border-color: var(--accent);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
  transform: translateY(-1px);
}

.csv-column-select .select-trigger.open {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(124, 77, 255, 0.1);
}

.csv-column-select .select-trigger.open .select-arrow {
  transform: rotate(180deg);
}

.csv-column-select .select-value {
  font-weight: 500;
  color: var(--text-primary);
}

.csv-column-select .select-arrow {
  color: var(--text-secondary);
  transition: transform 0.3s ease;
  flex-shrink: 0;
}

.csv-column-select .select-dropdown {
  position: absolute;
  top: calc(100% + 4px);
  left: 0;
  right: 0;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.12);
  z-index: 1000;
  opacity: 0;
  visibility: hidden;
  transform: translateY(-10px);
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  overflow-y: auto;
  max-height: 200px;
}

.csv-column-select .select-dropdown.open {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.csv-column-select .select-option {
  padding: 10px 12px;
  cursor: pointer;
  transition: all 0.2s ease;
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-primary);
  font-family: 'IBM Plex Sans', sans-serif;
}

.csv-column-select .select-option:hover {
  background: var(--bg-tertiary);
  transform: translateX(4px);
}

.csv-column-select .select-option.active {
  background: var(--accent);
  color: #fff;
}

.csv-column-select .select-option.active:hover {
  background: var(--accent-light);
  color: #fff;
  transform: translateX(0);
}

.csv-column-select .option-icon {
  font-size: 1rem;
  opacity: 0.7;
  width: 20px;
  text-align: center;
}

.csv-column-select .select-option.active .option-icon {
  opacity: 1;
}

.csv-fit-result {
  margin-top: 8px;
  padding-top: 12px;
  border-top: 1px solid var(--border-color);
}

.fit-result-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
}

.fit-reset-btn {
  width: 24px;
  height: 24px;
  padding: 0;
  background: transparent;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  font-size: 1.2rem;
  line-height: 1;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.15s ease;
  display: flex;
  align-items: center;
  justify-content: center;
}

.fit-reset-btn:hover {
  background: var(--bg-tertiary);
  border-color: var(--accent);
  color: var(--accent);
}

.fit-result-content {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.fit-item {
  padding: 10px 12px;
  background: var(--bg-tertiary);
  border: 1px solid transparent;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.fit-item:hover {
  border-color: var(--border-color);
}

.fit-item.active {
  border-color: var(--accent);
  background: var(--bg-secondary);
}

.fit-item.best-fit {
  background: var(--bg-secondary);
}

.fit-header {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 4px;
}

.fit-rank {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.7rem;
  padding: 2px 6px;
  background: var(--bg-tertiary);
  border-radius: 4px;
  color: var(--text-muted);
}

.fit-rank.best {
  background: var(--accent);
  color: white;
}

.fit-name {
  font-weight: 500;
  font-size: 0.9rem;
}

.fit-params {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-bottom: 2px;
}

.fit-score {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.75rem;
  color: var(--text-muted);
}

.csv-mode-msg {
  font-size: 0.9rem;
  color: var(--text-muted);
  font-style: italic;
}

/* Loading Overlay */
.loading-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(250, 250, 250, 0.9);
  display: none;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 16px;
  z-index: 1000;
}

.loading-overlay.active {
  display: flex;
}

.loading-spinner {
  width: 40px;
  height: 40px;
  border: 3px solid var(--border-color);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

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

.loading-text {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 0.85rem;
  color: var(--text-secondary);
}