/* ============================================================
   MATH QUIZ APP - MAIN STYLESHEET
   ============================================================
   Global variables, theme, typography, and shared components
   ============================================================ */

/* ------------------------------------------------------------
   1. CSS CUSTOM PROPERTIES (VARIABLES)
   ------------------------------------------------------------ */
:root {
  /* --- Primary Colors --- */
  --color-primary: #0b5ed7;
  --color-primary-light: #c5dcff;
  --color-primary-dark: #0a4fa8;
  
  /* --- Secondary Colors --- */
  --color-secondary: #6c757d;
  --color-secondary-light: #adb5bd;
  
  /* --- Success / Correct --- */
  --color-success: #2e7d32;
  --color-success-bg: #e6f4ea;
  --color-success-border: #4caf50;
  
  /* --- Danger / Wrong --- */
  --color-danger: #c62828;
  --color-danger-bg: #fde8e8;
  --color-danger-border: #ef5350;
  
  /* --- Warning --- */
  --color-warning: #856404;
  --color-warning-bg: #fff3cd;
  --color-warning-border: #ffc107;
  
  /* --- Info --- */
  --color-info: #0d6efd;
  --color-info-bg: #e8f0fe;
  
  /* --- Neutral --- */
  --color-white: #ffffff;
  --color-gray-50: #f8f9fa;
  --color-gray-100: #f0f4f8;
  --color-gray-200: #e9ecef;
  --color-gray-300: #dee2e6;
  --color-gray-400: #ced4da;
  --color-gray-500: #adb5bd;
  --color-gray-600: #6c757d;
  --color-gray-700: #495057;
  --color-gray-800: #343a40;
  --color-gray-900: #212529;
  --color-black: #000000;
  
  /* --- Background --- */
  --bg-main: #f0f4f8;
  --bg-card: #ffffff;
  --bg-sidebar: #0b5ed7;
  --bg-modal-overlay: rgba(0, 0, 0, 0.5);
  
  /* --- Typography --- */
  --font-primary: 'Roboto Slab', Georgia, 'Times New Roman', serif;
  --font-mono: 'Courier New', Courier, monospace;
  --font-size-xs: 0.7rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;
  --font-size-4xl: 2.25rem;
  
  /* --- 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: 0.25rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-2xl: 1.5rem;
  --radius-full: 9999px;
  
  /* --- Shadows --- */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.07);
  --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1);
  --shadow-xl: 0 20px 25px rgba(0, 0, 0, 0.15);
  
  /* --- Transitions --- */
  --transition-fast: 0.15s ease;
  --transition-base: 0.3s ease;
  --transition-slow: 0.5s ease;
  
  /* --- Layout --- */
  --sidebar-width: 260px;
  --header-height: 60px;
}

/* ------------------------------------------------------------
   2. CSS RESET & BASE STYLES
   ------------------------------------------------------------ */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  height: 100%;
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-primary);
  font-size: var(--font-size-base);
  line-height: 1.6;
  color: var(--color-gray-800);
  background-color: var(--bg-main);
  min-height: 100%;
  overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6 {
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: var(--spacing-sm);
}

h1 { font-size: var(--font-size-3xl); }
h2 { font-size: var(--font-size-2xl); }
h3 { font-size: var(--font-size-xl); }
h4 { font-size: var(--font-size-lg); }

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

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

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

img {
  max-width: 100%;
  height: auto;
}

/* ------------------------------------------------------------
   3. UTILITY CLASSES
   ------------------------------------------------------------ */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.text-primary { color: var(--color-primary); }
.text-success { color: var(--color-success); }
.text-danger { color: var(--color-danger); }
.text-warning { color: var(--color-warning); }
.text-muted { color: var(--color-gray-500); }

.bg-primary { background-color: var(--color-primary); }
.bg-success { background-color: var(--color-success-bg); }
.bg-danger { background-color: var(--color-danger-bg); }
.bg-warning { background-color: var(--color-warning-bg); }
.bg-light { background-color: var(--color-gray-50); }

.font-bold { font-weight: 700; }
.font-semibold { font-weight: 600; }
.font-medium { font-weight: 500; }
.font-normal { font-weight: 400; }

.text-xs { font-size: var(--font-size-xs); }
.text-sm { font-size: var(--font-size-sm); }
.text-base { font-size: var(--font-size-base); }
.text-lg { font-size: var(--font-size-lg); }
.text-xl { font-size: var(--font-size-xl); }
.text-2xl { font-size: var(--font-size-2xl); }
.text-3xl { font-size: var(--font-size-3xl); }

.uppercase { text-transform: uppercase; }
.capitalize { text-transform: capitalize; }

.hidden { display: none !important; }
.block { display: block; }
.inline-block { display: inline-block; }
.flex { display: flex; }
.inline-flex { display: inline-flex; }
.grid { display: grid; }

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

.w-full { width: 100%; }
.h-full { height: 100%; }

.relative { position: relative; }
.absolute { position: absolute; }
.fixed { position: fixed; }
.sticky { position: sticky; }

.overflow-auto { overflow: auto; }
.overflow-hidden { overflow: hidden; }

.rounded-sm { border-radius: var(--radius-sm); }
.rounded-md { border-radius: var(--radius-md); }
.rounded-lg { border-radius: var(--radius-lg); }
.rounded-xl { border-radius: var(--radius-xl); }
.rounded-2xl { border-radius: var(--radius-2xl); }
.rounded-full { border-radius: var(--radius-full); }

.shadow-sm { box-shadow: var(--shadow-sm); }
.shadow-md { box-shadow: var(--shadow-md); }
.shadow-lg { box-shadow: var(--shadow-lg); }
.shadow-xl { box-shadow: var(--shadow-xl); }

.transition { transition: all var(--transition-base); }

/* ------------------------------------------------------------
   4. BUTTON STYLES
   ------------------------------------------------------------ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  padding: 0.75rem 1.5rem;
  font-size: var(--font-size-base);
  font-weight: 600;
  font-family: var(--font-primary);
  border: none;
  border-radius: var(--radius-xl);
  cursor: pointer;
  transition: all var(--transition-fast);
  text-decoration: none;
  line-height: 1.5;
}

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

.btn:active {
  transform: translateY(0);
}

.btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  transform: none;
}

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

.btn-primary:hover {
  background-color: #a8c8ff;
  box-shadow: 0 4px 12px rgba(11, 94, 215, 0.2);
}

.btn-success {
  background-color: var(--color-success-bg);
  color: var(--color-success);
  border: 1px solid var(--color-success-border);
}

.btn-success:hover {
  background-color: #c8e6c9;
}

.btn-danger {
  background-color: var(--color-danger-bg);
  color: var(--color-danger);
  border: 1px solid var(--color-danger-border);
}

.btn-danger:hover {
  background-color: #ffcdd2;
}

.btn-outline {
  background-color: transparent;
  color: var(--color-gray-700);
  border: 2px solid var(--color-gray-200);
}

.btn-outline:hover {
  background-color: var(--color-gray-50);
  border-color: var(--color-gray-300);
}

.btn-lg {
  padding: 1rem 2rem;
  font-size: var(--font-size-lg);
}

.btn-sm {
  padding: 0.5rem 1rem;
  font-size: var(--font-size-sm);
}

.btn-block {
  width: 100%;
}

/* ------------------------------------------------------------
   5. FORM STYLES
   ------------------------------------------------------------ */
.form-group {
  margin-bottom: var(--spacing-lg);
}

.form-label {
  display: block;
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-gray-700);
  margin-bottom: var(--spacing-sm);
}

.form-control {
  width: 100%;
  padding: 0.75rem 1rem;
  font-size: var(--font-size-base);
  font-family: var(--font-primary);
  color: var(--color-gray-800);
  background-color: var(--color-white);
  border: 2px solid var(--color-gray-200);
  border-radius: var(--radius-xl);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.form-control:focus {
  outline: none;
  border-color: var(--color-primary-light);
  box-shadow: 0 0 0 3px rgba(11, 94, 215, 0.1);
}

.form-control:disabled {
  background-color: var(--color-gray-100);
  opacity: 0.7;
  cursor: not-allowed;
}

.form-control::placeholder {
  color: var(--color-gray-400);
}

select.form-control {
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%236c757d' viewBox='0 0 16 16'%3E%3Cpath d='M8 11L3 6h10l-5 5z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 1rem center;
  padding-right: 2.5rem;
}

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

.form-check {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.form-check-input {
  width: 1.2rem;
  height: 1.2rem;
  accent-color: var(--color-primary);
}

.form-error {
  color: var(--color-danger);
  font-size: var(--font-size-xs);
  margin-top: var(--spacing-xs);
}

.form-hint {
  color: var(--color-gray-500);
  font-size: var(--font-size-xs);
  margin-top: var(--spacing-xs);
}

/* ------------------------------------------------------------
   6. CARD COMPONENT
   ------------------------------------------------------------ */
.card {
  background-color: var(--bg-card);
  border-radius: var(--radius-2xl);
  box-shadow: var(--shadow-lg);
  padding: 0.5rem;
}

.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--spacing-lg);
  padding-bottom: var(--spacing-md);
  border-bottom: 1px solid var(--color-gray-200);
}

.card-body {
  margin-bottom: 0.5rem;
}

.card-footer {
  padding-top: var(--spacing-md);
  border-top: 1px solid var(--color-gray-200);
}

/* ------------------------------------------------------------
   7. MODAL COMPONENT
   ------------------------------------------------------------ */
.modal-overlay {
  position: fixed;
  inset: 0;
  background-color: var(--bg-modal-overlay);
  backdrop-filter: blur(4px);
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--spacing-md);
}

.modal-content {
  background-color: var(--bg-card);
  border-radius: var(--radius-2xl);
  box-shadow: var(--shadow-xl);
  width: 100%;
  max-width: 500px;
  max-height: 90vh;
  overflow-y: auto;
  animation: modalSlideIn var(--transition-base);
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--spacing-lg) var(--spacing-xl);
  background-color: var(--color-primary);
  color: var(--color-white);
  border-radius: var(--radius-2xl) var(--radius-2xl) 0 0;
}

.modal-header h3 {
  margin: 0;
  font-size: var(--font-size-lg);
}

.modal-close {
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: rgba(255, 255, 255, 0.2);
  color: var(--color-white);
  border: none;
  border-radius: var(--radius-full);
  cursor: pointer;
  font-size: var(--font-size-lg);
  transition: background-color var(--transition-fast);
}

.modal-close:hover {
  background-color: rgba(255, 255, 255, 0.3);
}

.modal-body {
  padding: var(--spacing-xl);
}

.modal-footer {
  display: flex;
  gap: var(--spacing-md);
  padding: var(--spacing-lg) var(--spacing-xl);
  border-top: 1px solid var(--color-gray-200);
}

/* ------------------------------------------------------------
   8. TABLE COMPONENT
   ------------------------------------------------------------ */
.table-responsive {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

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

table th {
  padding: 0.75rem 0.5rem;
  text-align: left;
  font-size: var(--font-size-xs);
  font-weight: 600;
  color: var(--color-gray-500);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  border-bottom: 2px solid var(--color-gray-200);
  white-space: nowrap;
}

table td {
  padding: 0.75rem 0.5rem;
  font-size: var(--font-size-sm);
  color: var(--color-gray-700);
  border-bottom: 1px solid var(--color-gray-100);
}

table tbody tr:hover {
  background-color: var(--color-gray-50);
}

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

/* ------------------------------------------------------------
   9. BADGE COMPONENT
   ------------------------------------------------------------ */
.badge {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  font-size: var(--font-size-xs);
  font-weight: 700;
  border-radius: var(--radius-full);
  letter-spacing: 0.5px;
}

.badge-primary {
  background-color: var(--color-info-bg);
  color: var(--color-primary);
}

.badge-success {
  background-color: var(--color-success-bg);
  color: var(--color-success);
}

.badge-danger {
  background-color: var(--color-danger-bg);
  color: var(--color-danger);
}

.badge-warning {
  background-color: var(--color-warning-bg);
  color: var(--color-warning);
}

.badge-secondary {
  background-color: var(--color-gray-200);
  color: var(--color-gray-600);
}

/* ------------------------------------------------------------
   10. SWITCH/TOGGLE COMPONENT
   ------------------------------------------------------------ */
.switch-track {
  width: 48px;
  height: 26px;
  border-radius: 13px;
  cursor: pointer;
  transition: background var(--transition-base);
  position: relative;
  display: inline-block;
}

.switch-track.on {
  background-color: var(--color-primary);
}

.switch-track.off {
  background-color: #ccc;
}

.switch-thumb {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background-color: var(--color-white);
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
  transition: transform var(--transition-base);
  position: absolute;
  top: 2px;
}

.switch-track.on .switch-thumb {
  transform: translateX(22px);
}

.switch-track.off .switch-thumb {
  transform: translateX(2px);
}

/* ------------------------------------------------------------
   11. PROGRESS BAR
   ------------------------------------------------------------ */
.progress {
  width: 100%;
  height: 8px;
  background-color: var(--color-gray-200);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.progress-bar {
  height: 100%;
  background-color: var(--color-primary);
  border-radius: var(--radius-full);
  transition: width 0.4s ease;
}

.progress-bar-success {
  background-color: var(--color-success);
}

.progress-bar-danger {
  background-color: var(--color-danger);
}

/* ------------------------------------------------------------
   12. ALERT COMPONENT
   ------------------------------------------------------------ */
.alert {
  padding: 1rem 1.25rem;
  border-radius: var(--radius-xl);
  font-size: var(--font-size-sm);
  margin-bottom: var(--spacing-md);
}

.alert-success {
  background-color: var(--color-success-bg);
  color: var(--color-success);
  border: 2px solid var(--color-success-border);
}

.alert-danger {
  background-color: var(--color-danger-bg);
  color: var(--color-danger);
  border: 2px solid var(--color-danger-border);
}

.alert-warning {
  background-color: var(--color-warning-bg);
  color: var(--color-warning);
  border: 2px solid var(--color-warning-border);
}

.alert-info {
  background-color: var(--color-info-bg);
  color: var(--color-info);
}

/* ------------------------------------------------------------
   13. AVATAR COMPONENT
   ------------------------------------------------------------ */
.avatar {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-full);
  object-fit: cover;
  border: 2px solid var(--color-white);
  box-shadow: var(--shadow-sm);
}

.avatar-sm {
  width: 36px;
  height: 36px;
}

.avatar-lg {
  width: 80px;
  height: 80px;
}

/* ------------------------------------------------------------
   14. LOADING SPINNER
   ------------------------------------------------------------ */
.spinner {
  display: inline-block;
  width: 24px;
  height: 24px;
  border: 3px solid var(--color-gray-200);
  border-top-color: var(--color-primary);
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}

.spinner-lg {
  width: 40px;
  height: 40px;
  border-width: 4px;
}

/* ------------------------------------------------------------
   15. EMPTY STATE
   ------------------------------------------------------------ */
.empty-state {
  text-align: center;
  padding: var(--spacing-2xl) var(--spacing-md);
}

.empty-state-icon {
  font-size: 3rem;
  color: var(--color-gray-300);
  margin-bottom: var(--spacing-md);
}

.empty-state-text {
  color: var(--color-gray-400);
  font-size: var(--font-size-sm);
}

/* ------------------------------------------------------------
   16. PAGINATION
   ------------------------------------------------------------ */
.pagination {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-md) 0;
}

.pagination-btn {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--color-gray-200);
  border-radius: var(--radius-md);
  background-color: var(--color-white);
  color: var(--color-gray-700);
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-primary);
}

.pagination-btn:hover {
  background-color: var(--color-gray-50);
  border-color: var(--color-primary);
  color: var(--color-primary);
}

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

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

/* ------------------------------------------------------------
   17. ANIMATIONS
   ------------------------------------------------------------ */
@keyframes fadeIn {
  from {
    opacity: 0;
    transform: scale(0.95);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes slideInRight {
  from {
    opacity: 0;
    transform: translateX(20px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

@keyframes pulse {
  0%, 100% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.05);
  }
}

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

@keyframes modalSlideIn {
  from {
    opacity: 0;
    transform: translateY(-10%) scale(0.95);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

.animate-in {
  animation: fadeIn var(--transition-base) ease forwards;
}

.animate-fade-in-up {
  animation: fadeInUp var(--transition-base) ease forwards;
}

.pulse {
  animation: pulse 0.6s ease;
}

/* ------------------------------------------------------------
   18. FRACTION DISPLAY STYLES (UNCHANGED FROM ORIGINAL)
   ------------------------------------------------------------ */
.fraction {
  display: inline-flex;
  flex-direction: column;
  vertical-align: middle;
  text-align: center;
  margin: 0 0.2em;
  line-height: 1;
}

.fraction > .numerator {
  display: block;
  border-bottom: 2px solid currentColor;
  padding: 0 0.3em 0.05em;
  line-height: 1.3;
}

.fraction > .denominator {
  display: block;
  padding: 0.05em 0.3em 0;
  line-height: 1.3;
}

.mixed-number {
  white-space: nowrap;
  display: inline-flex;
  align-items: center;
  gap: 0.1em;
}

.whole-number {
  line-height: 1;
}

/* ------------------------------------------------------------
   19. RESPONSIVE UTILITIES
   ------------------------------------------------------------ */
@media (max-width: 768px) {
  :root {
    --font-size-3xl: 1.5rem;
    --font-size-2xl: 1.25rem;
  }
  
  .card {
    padding: var(--spacing-md);
  }
  
  .modal-content {
    max-width: 95vw;
  }
  
  .hide-mobile {
    display: none !important;
  }
}

@media (min-width: 769px) {
  .hide-desktop {
    display: none !important;
  }
}

/* ------------------------------------------------------------
   20. PRINT STYLES (FOR REPORT)
   ------------------------------------------------------------ */
@media print {
  .no-print {
    display: none !important;
  }
  
  body {
    background-color: white;
  }
  
  .card {
    box-shadow: none;
    border: 1px solid #ddd;
  }
}