/* =====================
   CSS Variables
   ===================== */
:root {
  --primary: #0F172A;
  --primary-foreground: #FFFFFF;
  --primary-light: rgba(15, 23, 42, 0.1);
  --secondary: #F1F5F9;
  --secondary-foreground: #0F172A;
  --accent: #F97316;
  --accent-foreground: #FFFFFF;
  --background: #F8FAFC;
  --surface: #FFFFFF;
  --border: #E2E8F0;
  --text-main: #1E293B;
  --text-muted: #64748B;
  --success: #10B981;
  --success-light: rgba(16, 185, 129, 0.1);
  --error: #EF4444;
  --error-light: rgba(239, 68, 68, 0.1);
  --warning: #F59E0B;
  --warning-light: rgba(245, 158, 11, 0.1);
  
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
  
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  
  --font-heading: 'Manrope', sans-serif;
  --font-body: 'Inter', sans-serif;
}

/* =====================
   Reset & Base
   ===================== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-body);
  background-color: var(--background);
  color: var(--text-main);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: color 0.2s ease;
}

a:hover {
  color: var(--accent);
}

/* =====================
   Typography
   ===================== */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.3;
  color: var(--text-main);
}

h1 { font-size: 2.5rem; }
h2 { font-size: 1.5rem; }
h3 { font-size: 1.25rem; }

p {
  color: var(--text-muted);
}

/* =====================
   Layout
   ===================== */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
  width: 100%;
}

.main {
  flex: 1;
  padding: 2rem 0;
}

/* =====================
   Header
   ===================== */
.header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 1rem 0;
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-content {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1rem;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-heading);
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--primary);
}

.logo i {
  font-size: 1.75rem;
  color: var(--accent);
}

.logo:hover {
  color: var(--primary);
}

.tagline {
  font-size: 0.875rem;
  color: var(--text-muted);
}

.back-link {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.875rem;
  color: var(--text-muted);
}

.back-link:hover {
  color: var(--accent);
}

/* =====================
   Hero
   ===================== */
.hero {
  text-align: center;
  padding: 3rem 0;
  margin-bottom: 2rem;
}

.hero h1 {
  margin-bottom: 1rem;
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: 1.125rem;
  max-width: 600px;
  margin: 0 auto;
}

/* =====================
   Cards
   ===================== */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 2rem;
  box-shadow: var(--shadow-sm);
  margin-bottom: 1.5rem;
}

.card h2 {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border);
}

.card h2 i {
  color: var(--accent);
}

/* =====================
   Forms
   ===================== */
.form-group {
  margin-bottom: 1rem;
}

.form-group label {
  display: block;
  font-weight: 500;
  margin-bottom: 0.5rem;
  color: var(--text-main);
}

.form-group input,
.form-group select {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  font-family: inherit;
  font-size: 0.95rem;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
  background: var(--surface);
}

.form-group input:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-light);
}

.form-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 1rem;
  align-items: end;
}

/* File Upload */
.file-upload-area {
  border: 2px dashed var(--border);
  border-radius: var(--radius-lg);
  padding: 2rem;
  text-align: center;
  cursor: pointer;
  transition: border-color 0.2s ease, background 0.2s ease;
  position: relative;
}

.file-upload-area:hover {
  border-color: var(--accent);
  background: var(--primary-light);
}

.file-upload-area.drag-over {
  border-color: var(--accent);
  background: var(--primary-light);
}

.file-upload-area i {
  font-size: 3rem;
  color: var(--accent);
  margin-bottom: 1rem;
}

.file-upload-area p {
  margin-bottom: 0.5rem;
  color: var(--text-main);
}

.file-upload-area .file-types {
  font-size: 0.75rem;
  color: var(--text-muted);
}

.file-upload-area input[type="file"] {
  position: absolute;
  inset: 0;
  opacity: 0;
  cursor: pointer;
}

.selected-file {
  margin-top: 0.75rem;
  font-size: 0.875rem;
  color: var(--success);
  font-weight: 500;
}

/* =====================
   Buttons
   ===================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 500;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  transition: all 0.2s ease;
}

.btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

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

.btn-primary:hover:not(:disabled) {
  background: #1e293b;
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

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

.btn-secondary:hover:not(:disabled) {
  background: #e2e8f0;
}

.btn-accent {
  background: var(--accent);
  color: var(--accent-foreground);
}

.btn-accent:hover:not(:disabled) {
  background: #ea580c;
  transform: translateY(-1px);
}

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

.btn-danger:hover:not(:disabled) {
  background: #dc2626;
}

/* =====================
   Upload Status
   ===================== */
.upload-status {
  margin-top: 1rem;
  padding: 1rem;
  border-radius: var(--radius-md);
  display: none;
}

.upload-status.show {
  display: block;
}

.upload-status.success {
  background: var(--success-light);
  color: var(--success);
  border: 1px solid var(--success);
}

.upload-status.error {
  background: var(--error-light);
  color: var(--error);
  border: 1px solid var(--error);
}

.upload-status.loading {
  background: var(--warning-light);
  color: var(--warning);
  border: 1px solid var(--warning);
}

/* =====================
   Section Header
   ===================== */
.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.5rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border);
}

.section-header h2 {
  margin: 0;
  padding: 0;
  border: none;
}

/* =====================
   Datasets List
   ===================== */
.datasets-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1rem;
}

.dataset-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  transition: box-shadow 0.2s ease, transform 0.2s ease;
  cursor: pointer;
}

.dataset-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
  border-color: var(--accent);
}

.dataset-card h3 {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
  font-size: 1rem;
}

.dataset-card h3 i {
  color: var(--accent);
}

.dataset-card .meta {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  font-size: 0.8rem;
  color: var(--text-muted);
}

.dataset-card .meta span {
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.dataset-card .meta i {
  font-size: 0.9rem;
}

/* Empty State */
.empty-state {
  text-align: center;
  padding: 3rem;
  color: var(--text-muted);
}

.empty-state i {
  font-size: 4rem;
  margin-bottom: 1rem;
  opacity: 0.3;
}

/* =====================
   Loading
   ===================== */
.loading {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  padding: 2rem;
  color: var(--text-muted);
}

.loading i {
  animation: spin 1s linear infinite;
}

@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

/* =====================
   Dataset Page
   ===================== */
.dataset-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1rem;
}

.dataset-header h1 {
  font-size: 1.75rem;
  margin-bottom: 0.5rem;
}

.dataset-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 1.5rem;
  font-size: 0.875rem;
  color: var(--text-muted);
}

.dataset-meta span {
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.dataset-actions {
  display: flex;
  gap: 0.5rem;
}

/* =====================
   Tabs
   ===================== */
.tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
  padding: 0.5rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
}

.tab-btn {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1rem;
  font-family: inherit;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-muted);
  background: transparent;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all 0.2s ease;
}

.tab-btn:hover {
  color: var(--text-main);
  background: var(--secondary);
}

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

.tab-btn i {
  font-size: 1rem;
}

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
}

/* =====================
   Tables
   ===================== */
.table-wrapper {
  overflow-x: auto;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.875rem;
}

thead {
  background: var(--secondary);
  position: sticky;
  top: 0;
}

th {
  text-align: left;
  padding: 0.875rem 1rem;
  font-weight: 600;
  color: var(--text-main);
  border-bottom: 1px solid var(--border);
  white-space: nowrap;
}

td {
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border);
  color: var(--text-muted);
}

tr:last-child td {
  border-bottom: none;
}

tbody tr:hover {
  background: var(--secondary);
}

/* =====================
   Statistics
   ===================== */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1rem;
}

.stat-card {
  background: var(--secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 1.25rem;
}

.stat-card h4 {
  font-size: 0.9rem;
  color: var(--text-main);
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.stat-card h4 .dtype {
  font-size: 0.7rem;
  font-weight: 400;
  color: var(--accent);
  background: var(--surface);
  padding: 0.15rem 0.5rem;
  border-radius: var(--radius-sm);
}

.stat-item {
  display: flex;
  justify-content: space-between;
  padding: 0.35rem 0;
  font-size: 0.8rem;
  border-bottom: 1px dashed var(--border);
}

.stat-item:last-child {
  border-bottom: none;
}

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

.stat-item .value {
  color: var(--text-main);
  font-weight: 500;
}

/* =====================
   Filter & Groupby Results
   ===================== */
.filter-results,
.groupby-results {
  margin-top: 1.5rem;
}

.result-info {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1rem;
  padding: 0.75rem 1rem;
  background: var(--success-light);
  border: 1px solid var(--success);
  border-radius: var(--radius-md);
  color: var(--success);
  font-size: 0.875rem;
}

.result-info i {
  font-size: 1.25rem;
}

/* =====================
   Correlation Matrix
   ===================== */
.correlation-table {
  overflow-x: auto;
}

.correlation-table table {
  font-size: 0.8rem;
}

.correlation-table th,
.correlation-table td {
  text-align: center;
  min-width: 80px;
}

.correlation-table td {
  font-weight: 500;
}

.corr-positive {
  background: rgba(16, 185, 129, var(--corr-intensity, 0.1));
}

.corr-negative {
  background: rgba(239, 68, 68, var(--corr-intensity, 0.1));
}

/* =====================
   Charts
   ===================== */
.chart-controls {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  align-items: end;
  margin-bottom: 1.5rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--border);
}

.chart-controls .form-group {
  margin-bottom: 0;
  min-width: 150px;
}

.chart-container {
  position: relative;
  height: 400px;
  background: var(--secondary);
  border-radius: var(--radius-md);
  padding: 1rem;
}

/* =====================
   Logs
   ===================== */
.logs-list {
  max-height: 300px;
  overflow-y: auto;
}

.log-item {
  display: flex;
  align-items: flex-start;
  gap: 1rem;
  padding: 0.75rem;
  border-bottom: 1px solid var(--border);
  font-size: 0.8rem;
}

.log-item:last-child {
  border-bottom: none;
}

.log-item .action {
  font-weight: 600;
  color: var(--primary);
  min-width: 80px;
}

.log-item .time {
  color: var(--text-muted);
  font-size: 0.75rem;
}

.log-item .details {
  color: var(--text-muted);
  flex: 1;
}

/* =====================
   Description
   ===================== */
.description {
  font-size: 0.875rem;
  color: var(--text-muted);
  margin-bottom: 1.5rem;
  padding: 1rem;
  background: var(--secondary);
  border-radius: var(--radius-md);
}

/* =====================
   Footer
   ===================== */
.footer {
  background: var(--primary);
  color: var(--primary-foreground);
  padding: 1.5rem 0;
  margin-top: auto;
}

.footer p {
  color: rgba(255, 255, 255, 0.7);
  font-size: 0.875rem;
  text-align: center;
}

/* =====================
   Responsive
   ===================== */
@media (max-width: 768px) {
  h1 { font-size: 1.75rem; }
  h2 { font-size: 1.25rem; }
  
  .hero {
    padding: 2rem 0;
  }
  
  .card {
    padding: 1.25rem;
  }
  
  .dataset-header {
    flex-direction: column;
  }
  
  .tabs {
    overflow-x: auto;
    flex-wrap: nowrap;
  }
  
  .tab-btn {
    white-space: nowrap;
    padding: 0.5rem 0.75rem;
    font-size: 0.8rem;
  }
  
  .form-row {
    grid-template-columns: 1fr;
  }
  
  .chart-container {
    height: 300px;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 1rem;
  }
  
  .logo {
    font-size: 1.25rem;
  }
  
  .tagline {
    display: none;
  }
  
  .datasets-grid {
    grid-template-columns: 1fr;
  }
  
  .stats-grid {
    grid-template-columns: 1fr;
  }
}