/* ===================================
   Check-The-Sum - Modern CSS Framework
   =================================== */

:root {
  /* Color Palette - Light Mode */
  --primary: #2563eb;
  --primary-dark: #1e40af;
  --primary-light: #3b82f6;
  --secondary: #7c3aed;
  --accent: #06b6d4;

  --success: #10b981;
  --warning: #f59e0b;
  --danger: #ef4444;
  --info: #3b82f6;

  /* Neutrals */
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-tertiary: #f1f5f9;
  --bg-elevated: #ffffff;

  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-tertiary: #94a3b8;

  --border-color: #e2e8f0;
  --border-light: #f1f5f9;

  /* Shadows */
  --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);
  --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);

  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;

  /* Border Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;

  /* Transitions */
  --transition-fast: 150ms ease-in-out;
  --transition-base: 200ms ease-in-out;
  --transition-slow: 300ms ease-in-out;
}

[data-theme="dark"] {
  --primary: #3b82f6;
  --primary-dark: #2563eb;
  --primary-light: #60a5fa;

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

  --text-primary: #f1f5f9;
  --text-secondary: #cbd5e1;
  --text-tertiary: #64748b;

  --border-color: #334155;
  --border-light: #1e293b;

  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.3);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.4), 0 2px 4px -2px rgb(0 0 0 / 0.4);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.5), 0 4px 6px -4px rgb(0 0 0 / 0.5);
  --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.6), 0 8px 10px -6px rgb(0 0 0 / 0.6);
}

/* ===================================
   Base Styles
   =================================== */

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

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  line-height: 1.6;
  transition: background-color var(--transition-base), color var(--transition-base);
}

/* ===================================
   Typography
   =================================== */

h1, h2, h3, h4, h5, h6 {
  font-weight: 700;
  line-height: 1.2;
  color: var(--text-primary);
}

h1 { font-size: 2.5rem; margin-bottom: var(--spacing-lg); }
h2 { font-size: 2rem; margin-bottom: var(--spacing-md); }
h3 { font-size: 1.5rem; margin-bottom: var(--spacing-md); }
h4 { font-size: 1.25rem; margin-bottom: var(--spacing-sm); }
h5 { font-size: 1.125rem; margin-bottom: var(--spacing-sm); }
h6 { font-size: 1rem; margin-bottom: var(--spacing-sm); }

p {
  margin-bottom: var(--spacing-md);
  color: var(--text-secondary);
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--primary-dark);
  text-decoration: underline;
}

/* ===================================
   Layout Components
   =================================== */

.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

.container-narrow {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

.grid {
  display: grid;
  gap: var(--spacing-lg);
}

.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }

@media (max-width: 1024px) {
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 640px) {
  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }
}

/* ===================================
   Header & Navigation
   =================================== */

.header {
  background-color: var(--bg-elevated);
  border-bottom: 1px solid var(--border-color);
  box-shadow: var(--shadow-sm);
  position: sticky;
  top: 0;
  z-index: 1000;
  transition: all var(--transition-base);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--spacing-md) 0;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
  text-decoration: none;
}

.nav-brand:hover {
  text-decoration: none;
  color: var(--primary);
}

.nav-logo {
  width: 40px;
  height: 40px;
}

.nav-menu {
  display: flex;
  gap: var(--spacing-md);
  list-style: none;
  align-items: center;
}

.nav-link {
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--radius-md);
  color: var(--text-secondary);
  font-weight: 500;
  transition: all var(--transition-fast);
}

.nav-link:hover {
  background-color: var(--bg-tertiary);
  color: var(--text-primary);
  text-decoration: none;
}

.nav-link.active {
  background-color: var(--primary);
  color: white;
}

/* Mobile Navigation */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 1.5rem;
  color: var(--text-primary);
  cursor: pointer;
}

@media (max-width: 768px) {
  .nav-toggle {
    display: block;
  }

  .nav-menu {
    position: fixed;
    top: 70px;
    left: 0;
    right: 0;
    flex-direction: column;
    background-color: var(--bg-elevated);
    border-bottom: 1px solid var(--border-color);
    padding: var(--spacing-md);
    transform: translateY(-150%);
    transition: transform var(--transition-base);
    box-shadow: var(--shadow-lg);
  }

  .nav-menu.active {
    transform: translateY(0);
  }
}

/* ===================================
   Cards
   =================================== */

.card {
  background-color: var(--bg-elevated);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  box-shadow: var(--shadow-sm);
  transition: all var(--transition-base);
}

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

.card-header {
  margin-bottom: var(--spacing-md);
  padding-bottom: var(--spacing-md);
  border-bottom: 1px solid var(--border-color);
}

.card-title {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: var(--spacing-xs);
}

.card-description {
  color: var(--text-secondary);
  font-size: 0.875rem;
}

.card-body {
  margin-bottom: var(--spacing-md);
}

.card-footer {
  margin-top: var(--spacing-md);
  padding-top: var(--spacing-md);
  border-top: 1px solid var(--border-color);
  display: flex;
  gap: var(--spacing-sm);
  align-items: center;
  justify-content: space-between;
}

/* ===================================
   Buttons
   =================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-sm) var(--spacing-lg);
  font-size: 0.875rem;
  font-weight: 500;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  transition: all var(--transition-fast);
  text-decoration: none;
  white-space: nowrap;
}

.btn:hover {
  text-decoration: none;
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

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

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

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

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

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

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

.btn-sm {
  padding: var(--spacing-xs) var(--spacing-md);
  font-size: 0.8rem;
}

.btn-lg {
  padding: var(--spacing-md) var(--spacing-xl);
  font-size: 1rem;
}

.btn-icon {
  padding: var(--spacing-sm);
  width: 36px;
  height: 36px;
}

/* ===================================
   Forms
   =================================== */

.form-group {
  margin-bottom: var(--spacing-md);
}

.form-label {
  display: block;
  margin-bottom: var(--spacing-xs);
  font-weight: 500;
  color: var(--text-primary);
  font-size: 0.875rem;
}

.form-input,
.form-select,
.form-textarea {
  width: 100%;
  padding: var(--spacing-sm) var(--spacing-md);
  font-size: 0.875rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  transition: all var(--transition-fast);
}

.form-input:focus,
.form-select:focus,
.form-textarea:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-textarea {
  resize: vertical;
  min-height: 100px;
}

/* ===================================
   Stats & Metrics
   =================================== */

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
}

.stat-card {
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
  color: white;
  padding: var(--spacing-lg);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  transition: all var(--transition-base);
}

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

.stat-card.success {
  background: linear-gradient(135deg, var(--success) 0%, #059669 100%);
}

.stat-card.warning {
  background: linear-gradient(135deg, var(--warning) 0%, #d97706 100%);
}

.stat-card.danger {
  background: linear-gradient(135deg, var(--danger) 0%, #dc2626 100%);
}

.stat-card.info {
  background: linear-gradient(135deg, var(--info) 0%, var(--primary-dark) 100%);
}

.stat-label {
  font-size: 0.875rem;
  opacity: 0.9;
  margin-bottom: var(--spacing-xs);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.stat-value {
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: var(--spacing-xs);
}

.stat-change {
  font-size: 0.875rem;
  opacity: 0.9;
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
}

/* ===================================
   Badges
   =================================== */

.badge {
  display: inline-flex;
  align-items: center;
  padding: var(--spacing-xs) var(--spacing-sm);
  font-size: 0.75rem;
  font-weight: 600;
  border-radius: var(--radius-sm);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.badge-primary { background-color: #dbeafe; color: #1e40af; }
.badge-success { background-color: #d1fae5; color: #065f46; }
.badge-warning { background-color: #fef3c7; color: #92400e; }
.badge-danger { background-color: #fee2e2; color: #991b1b; }
.badge-info { background-color: #e0e7ff; color: #3730a3; }

[data-theme="dark"] .badge-primary { background-color: #1e3a8a; color: #dbeafe; }
[data-theme="dark"] .badge-success { background-color: #064e3b; color: #d1fae5; }
[data-theme="dark"] .badge-warning { background-color: #78350f; color: #fef3c7; }
[data-theme="dark"] .badge-danger { background-color: #7f1d1d; color: #fee2e2; }
[data-theme="dark"] .badge-info { background-color: #312e81; color: #e0e7ff; }

/* ===================================
   Tables
   =================================== */

.table-container {
  overflow-x: auto;
  background-color: var(--bg-elevated);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-sm);
}

.table {
  width: 100%;
  border-collapse: collapse;
}

.table th,
.table td {
  padding: var(--spacing-md);
  text-align: left;
  border-bottom: 1px solid var(--border-color);
}

.table th {
  background-color: var(--bg-tertiary);
  font-weight: 600;
  font-size: 0.875rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-secondary);
}

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

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

/* ===================================
   Search & Filters
   =================================== */

.search-container {
  background-color: var(--bg-elevated);
  padding: var(--spacing-xl);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-md);
  margin-bottom: var(--spacing-xl);
}

.search-bar {
  position: relative;
  margin-bottom: var(--spacing-md);
}

.search-bar input {
  padding-left: 2.5rem;
}

.search-icon {
  position: absolute;
  left: var(--spacing-md);
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-tertiary);
  pointer-events: none;
}

.filter-group {
  display: flex;
  gap: var(--spacing-md);
  flex-wrap: wrap;
  align-items: center;
}

/* ===================================
   Charts
   =================================== */

.chart-container {
  background-color: var(--bg-elevated);
  padding: var(--spacing-lg);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-sm);
  margin-bottom: var(--spacing-lg);
}

.chart-header {
  margin-bottom: var(--spacing-lg);
}

.chart-title {
  font-size: 1.125rem;
  font-weight: 600;
  margin-bottom: var(--spacing-xs);
}

.chart-description {
  font-size: 0.875rem;
  color: var(--text-secondary);
}

/* ===================================
   Dark Mode Toggle
   =================================== */

.theme-toggle {
  position: relative;
  width: 60px;
  height: 30px;
  background-color: var(--bg-tertiary);
  border-radius: 15px;
  border: 2px solid var(--border-color);
  cursor: pointer;
  transition: all var(--transition-base);
}

.theme-toggle::before {
  content: '🌙';
  position: absolute;
  top: 2px;
  left: 2px;
  width: 22px;
  height: 22px;
  background-color: var(--bg-elevated);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.75rem;
  transition: all var(--transition-base);
  box-shadow: var(--shadow-sm);
}

[data-theme="dark"] .theme-toggle::before {
  content: '☀️';
  transform: translateX(30px);
}

[data-theme="dark"] .theme-toggle {
  background-color: var(--primary);
}

/* ===================================
   Alerts & Notifications
   =================================== */

.alert {
  padding: var(--spacing-md);
  border-radius: var(--radius-md);
  margin-bottom: var(--spacing-md);
  border-left: 4px solid;
  display: flex;
  align-items: start;
  gap: var(--spacing-md);
}

.alert-info {
  background-color: #dbeafe;
  border-color: var(--info);
  color: #1e40af;
}

.alert-success {
  background-color: #d1fae5;
  border-color: var(--success);
  color: #065f46;
}

.alert-warning {
  background-color: #fef3c7;
  border-color: var(--warning);
  color: #92400e;
}

.alert-danger {
  background-color: #fee2e2;
  border-color: var(--danger);
  color: #991b1b;
}

[data-theme="dark"] .alert-info { background-color: #1e3a8a; color: #dbeafe; }
[data-theme="dark"] .alert-success { background-color: #064e3b; color: #d1fae5; }
[data-theme="dark"] .alert-warning { background-color: #78350f; color: #fef3c7; }
[data-theme="dark"] .alert-danger { background-color: #7f1d1d; color: #fee2e2; }

/* ===================================
   Loading States
   =================================== */

.spinner {
  width: 40px;
  height: 40px;
  border: 4px solid var(--border-color);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 1s linear infinite;
}

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

.skeleton {
  background: linear-gradient(90deg, var(--bg-tertiary) 25%, var(--border-color) 50%, var(--bg-tertiary) 75%);
  background-size: 200% 100%;
  animation: loading 1.5s ease-in-out infinite;
  border-radius: var(--radius-md);
}

@keyframes loading {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

/* ===================================
   Utilities
   =================================== */

.mt-1 { margin-top: var(--spacing-xs); }
.mt-2 { margin-top: var(--spacing-sm); }
.mt-3 { margin-top: var(--spacing-md); }
.mt-4 { margin-top: var(--spacing-lg); }
.mt-5 { margin-top: var(--spacing-xl); }

.mb-1 { margin-bottom: var(--spacing-xs); }
.mb-2 { margin-bottom: var(--spacing-sm); }
.mb-3 { margin-bottom: var(--spacing-md); }
.mb-4 { margin-bottom: var(--spacing-lg); }
.mb-5 { margin-bottom: var(--spacing-xl); }

.text-center { text-align: center; }
.text-right { text-align: right; }
.text-left { text-align: left; }

.text-primary { color: var(--primary); }
.text-secondary { color: var(--text-secondary); }
.text-success { color: var(--success); }
.text-warning { color: var(--warning); }
.text-danger { color: var(--danger); }

.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.justify-center { justify-content: center; }
.gap-1 { gap: var(--spacing-xs); }
.gap-2 { gap: var(--spacing-sm); }
.gap-3 { gap: var(--spacing-md); }
.gap-4 { gap: var(--spacing-lg); }

.hidden { display: none; }
.block { display: block; }

/* ===================================
   Hero Section
   =================================== */

.hero {
  background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
  color: white;
  padding: var(--spacing-md) var(--spacing-lg);
  text-align: center;
  margin: var(--spacing-lg) 0;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
}

.hero h1 {
  color: white;
  font-size: 1.5rem;
  margin-bottom: var(--spacing-xs);
}

.hero p {
  color: rgba(255, 255, 255, 0.9);
  font-size: 0.9rem;
  max-width: 700px;
  margin: 0 auto var(--spacing-xs);
}

/* ===================================
   Footer
   =================================== */

.footer {
  background-color: var(--bg-elevated);
  border-top: 1px solid var(--border-color);
  padding: var(--spacing-xl) 0;
  margin-top: var(--spacing-2xl);
}

.footer-content {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-xl);
}

.footer-section h3 {
  margin-bottom: var(--spacing-md);
  font-size: 1rem;
}

.footer-links {
  list-style: none;
}

.footer-links li {
  margin-bottom: var(--spacing-sm);
}

.footer-links a {
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}

.footer-links a:hover {
  color: var(--primary);
  text-decoration: none;
}

.footer-bottom {
  text-align: center;
  margin-top: var(--spacing-xl);
  padding-top: var(--spacing-lg);
  border-top: 1px solid var(--border-color);
  color: var(--text-tertiary);
  font-size: 0.875rem;
}

/* ===================================
   Responsive Design
   =================================== */

@media (max-width: 768px) {
  html { font-size: 14px; }

  h1 { font-size: 2rem; }
  h2 { font-size: 1.75rem; }
  h3 { font-size: 1.5rem; }

  .hero h1 { font-size: 2rem; }
  .hero p { font-size: 1rem; }

  .stat-value { font-size: 2rem; }

  .container, .container-narrow {
    padding: 0 var(--spacing-md);
  }
}