/* ========================================
   Mathvidya - Main Stylesheet
   Modern, Clean, Student-Friendly Design
   ======================================== */

/* ========== CSS Variables (Design System) ========== */
:root {
  /* Primary Colors */
  --color-primary: #6366F1;
  --color-primary-dark: #4F46E5;
  --color-primary-light: #818CF8;

  --color-secondary: #EC4899;
  --color-secondary-dark: #DB2777;
  --color-secondary-light: #F472B6;

  /* Accent Colors */
  --color-accent: #10B981;
  --color-warning: #F59E0B;
  --color-error: #EF4444;
  --color-info: #3B82F6;

  /* Neutral Colors */
  --color-dark: #1F2937;
  --color-gray-800: #1F2937;
  --color-gray-700: #374151;
  --color-gray-600: #4B5563;
  --color-gray-500: #6B7280;
  --color-gray-400: #9CA3AF;
  --color-gray-300: #D1D5DB;
  --color-gray-200: #E5E7EB;
  --color-gray-100: #F3F4F6;
  --color-gray-50: #F9FAFB;
  --color-white: #FFFFFF;

  /* Gradients */
  --gradient-primary: linear-gradient(135deg, #6366F1 0%, #8B5CF6 50%, #EC4899 100%);
  --gradient-success: linear-gradient(135deg, #10B981 0%, #14B8A6 100%);
  --gradient-card: linear-gradient(135deg, rgba(99, 102, 241, 0.1) 0%, rgba(236, 72, 153, 0.1) 100%);

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  --shadow-glow: 0 0 20px rgba(99, 102, 241, 0.3);

  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  --spacing-3xl: 4rem;

  /* Border Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  /* Typography */
  --font-heading: 'Poppins', sans-serif;
  --font-body: 'Inter', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  /* Font Sizes */
  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;
  --text-3xl: 1.875rem;
  --text-4xl: 2.25rem;
  --text-5xl: 3rem;
  --text-6xl: 3.75rem;

  /* Transitions */
  --transition-fast: 150ms ease-in-out;
  --transition-base: 300ms ease-in-out;
  --transition-slow: 500ms ease-in-out;

  /* Z-index layers */
  --z-base: 0;
  --z-dropdown: 1000;
  --z-sticky: 1020;
  --z-fixed: 1030;
  --z-modal: 1040;
  --z-popover: 1050;
  --z-tooltip: 1060;
}

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

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

body {
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--color-gray-800);
  background-color: var(--color-gray-50);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ========== Typography ========== */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 600;
  line-height: 1.2;
  color: var(--color-gray-900);
  margin-bottom: var(--spacing-md);
}

h1 { font-size: var(--text-5xl); }
h2 { font-size: var(--text-4xl); }
h3 { font-size: var(--text-3xl); }
h4 { font-size: var(--text-2xl); }
h5 { font-size: var(--text-xl); }
h6 { font-size: var(--text-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);
}

/* ========== Buttons ========== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  padding: 0.75rem 1.5rem;
  font-family: var(--font-heading);
  font-size: var(--text-base);
  font-weight: 600;
  line-height: 1;
  text-align: center;
  text-decoration: none;
  white-space: nowrap;
  border: none;
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all var(--transition-base);
  box-shadow: var(--shadow-sm);
}

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

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

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

/* Button Variants */
.btn-primary {
  background: var(--gradient-primary);
  color: var(--color-white);
}

.btn-primary:hover {
  box-shadow: var(--shadow-xl), var(--shadow-glow);
}

.btn-secondary {
  background-color: var(--color-gray-200);
  color: var(--color-gray-800);
}

.btn-secondary:hover {
  background-color: var(--color-gray-300);
}

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

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

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

.btn-ghost {
  background-color: transparent;
  color: var(--color-primary);
  box-shadow: none;
}

.btn-ghost:hover {
  background-color: var(--color-gray-100);
}

/* Button Sizes */
.btn-sm {
  padding: 0.5rem 1rem;
  font-size: var(--text-sm);
}

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

.btn-icon {
  padding: 0.75rem;
  aspect-ratio: 1;
}

/* ========== Cards ========== */
.card {
  background-color: var(--color-white);
  border-radius: var(--radius-xl);
  padding: var(--spacing-xl);
  box-shadow: var(--shadow-md);
  transition: all var(--transition-base);
}

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

.card-interactive {
  cursor: pointer;
}

.card-interactive:hover {
  box-shadow: var(--shadow-xl), 0 0 0 2px var(--color-primary-light);
}

.card-gradient {
  background: var(--gradient-card);
  backdrop-filter: blur(10px);
}

/* ========== Form Elements ========== */
.form-group {
  margin-bottom: var(--spacing-lg);
}

.form-label {
  display: block;
  margin-bottom: var(--spacing-sm);
  font-weight: 500;
  color: var(--color-gray-700);
}

.form-input,
.form-select,
.form-textarea {
  width: 100%;
  padding: 0.75rem 1rem;
  font-family: var(--font-body);
  font-size: var(--text-base);
  color: var(--color-gray-800);
  background-color: var(--color-white);
  border: 2px solid var(--color-gray-300);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.form-input:focus,
.form-select:focus,
.form-textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.form-input.error {
  border-color: var(--color-error);
}

.form-error {
  display: block;
  margin-top: var(--spacing-xs);
  font-size: var(--text-sm);
  color: var(--color-error);
}

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

/* Checkbox & Radio */
.form-checkbox,
.form-radio {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  cursor: pointer;
}

.form-checkbox input,
.form-radio input {
  width: 1.25rem;
  height: 1.25rem;
  cursor: pointer;
}

/* ========== Badges & Tags ========== */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 0.25rem 0.75rem;
  font-size: var(--text-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  border-radius: var(--radius-full);
}

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

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

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

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

.badge-gray {
  background-color: var(--color-gray-200);
  color: var(--color-gray-800);
}

/* ========== Alerts ========== */
.alert {
  padding: var(--spacing-md);
  border-radius: var(--radius-md);
  margin-bottom: var(--spacing-md);
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.alert-success {
  background-color: #D1FAE5;
  color: #065F46;
  border: 1px solid #10B981;
}

.alert-error {
  background-color: #FEE2E2;
  color: #991B1B;
  border: 1px solid #EF4444;
}

.alert-warning {
  background-color: #FEF3C7;
  color: #92400E;
  border: 1px solid #F59E0B;
}

.alert-info {
  background-color: #DBEAFE;
  color: #1E40AF;
  border: 1px solid #3B82F6;
}

/* ========== Loading States ========== */
.spinner {
  width: 2rem;
  height: 2rem;
  border: 3px solid var(--color-gray-200);
  border-top-color: var(--color-primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

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

.skeleton {
  background: linear-gradient(
    90deg,
    var(--color-gray-200) 25%,
    var(--color-gray-300) 50%,
    var(--color-gray-200) 75%
  );
  background-size: 200% 100%;
  animation: skeleton-loading 1.5s ease-in-out infinite;
  border-radius: var(--radius-md);
}

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

/* ========== Utility Classes ========== */

/* Spacing */
.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); }

.pt-3 { padding-top: var(--spacing-md); }
.pb-3 { padding-bottom: var(--spacing-md); }
.py-3 { padding-top: var(--spacing-md); padding-bottom: var(--spacing-md); }
.px-3 { padding-left: var(--spacing-md); padding-right: var(--spacing-md); }

/* Text */
.text-center { text-align: center; }
.text-right { text-align: right; }
.text-left { text-align: left; }

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

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

.text-primary { color: var(--color-primary); }
.text-secondary { color: var(--color-secondary); }
.text-success { color: var(--color-accent); }
.text-error { color: var(--color-error); }
.text-gray { color: var(--color-gray-600); }

/* Display */
.flex { display: flex; }
.inline-flex { display: inline-flex; }
.grid { display: grid; }
.hidden { display: none; }

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

/* Positioning */
.relative { position: relative; }
.absolute { position: absolute; }
.fixed { position: fixed; }

/* Misc */
.w-full { width: 100%; }
.h-full { height: 100%; }
.rounded { border-radius: var(--radius-md); }
.rounded-lg { border-radius: var(--radius-lg); }
.rounded-full { border-radius: var(--radius-full); }
.shadow { box-shadow: var(--shadow-md); }
.shadow-lg { box-shadow: var(--shadow-lg); }

/* ========== Animations ========== */
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

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

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

@keyframes scaleIn {
  from {
    opacity: 0;
    transform: scale(0.9);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

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

.animate-slideUp {
  animation: slideUp var(--transition-base);
}

.animate-slideDown {
  animation: slideDown var(--transition-base);
}

.animate-scaleIn {
  animation: scaleIn var(--transition-base);
}

/* ========== Responsive Breakpoints ========== */
@media (max-width: 768px) {
  :root {
    --text-5xl: 2.5rem;
    --text-4xl: 2rem;
    --text-3xl: 1.75rem;
  }

  .btn {
    padding: 0.625rem 1.25rem;
    font-size: var(--text-sm);
  }

  .card {
    padding: var(--spacing-lg);
  }
}

/* ========== Print Styles ========== */
@media print {
  .no-print {
    display: none !important;
  }
}