/**
 * UG2 Portal Design System
 * Unified styles for accessibility, consistency, and mobile responsiveness
 * Version: 1.0.0
 */

/* ============================================
   CSS Custom Properties (Design Tokens)
   ============================================ */
:root {
  /* Colors - Primary */
  --color-primary: #0052CC;
  --color-primary-dark: #0043A3;
  --color-primary-light: #0065FF;

  /* Colors - Secondary (Green theme for students) */
  --color-secondary: #36B37E;
  --color-secondary-dark: #00875A;
  --color-secondary-light: #57D9A3;

  /* Colors - Semantic */
  --color-success: #36B37E;
  --color-success-bg: #E3FCEF;
  --color-success-border: #ABF5D1;

  --color-error: #DE350B;
  --color-error-bg: #FFEBE6;
  --color-error-border: #FFBDAD;

  --color-warning: #FF991F;
  --color-warning-bg: #FFFAE6;
  --color-warning-border: #FFE380;

  --color-info: #0052CC;
  --color-info-bg: #DEEBFF;
  --color-info-border: #B3D4FF;

  /* Colors - Neutral */
  --color-text-primary: #172B4D;
  --color-text-secondary: #5E6C84;
  --color-text-muted: #6B778C;
  --color-text-disabled: #A5ADBA;

  --color-bg-primary: #FFFFFF;
  --color-bg-secondary: #FAFBFC;
  --color-bg-tertiary: #F4F5F7;

  --color-border: #DFE1E6;
  --color-border-light: #EBECF0;
  --color-border-dark: #C1C7D0;

  /* Spacing */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;

  /* Typography */
  --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', sans-serif;
  --font-size-xs: 12px;
  --font-size-sm: 14px;
  --font-size-md: 16px;
  --font-size-lg: 18px;
  --font-size-xl: 20px;
  --font-size-2xl: 24px;
  --font-size-3xl: 28px;

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

  --line-height-tight: 1.25;
  --line-height-normal: 1.5;
  --line-height-relaxed: 1.75;

  /* Border Radius */
  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 8px;
  --radius-xl: 12px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 8px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 8px 16px rgba(0, 0, 0, 0.15);
  --shadow-xl: 0 12px 24px rgba(0, 0, 0, 0.2);

  /* Focus ring for accessibility */
  --focus-ring: 0 0 0 3px rgba(0, 82, 204, 0.4);
  --focus-ring-success: 0 0 0 3px rgba(54, 179, 126, 0.4);
  --focus-ring-error: 0 0 0 3px rgba(222, 53, 11, 0.4);

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-normal: 200ms ease;
  --transition-slow: 300ms ease;

  /* Touch targets - WCAG 2.5.5 minimum 44px, recommended 48px */
  --touch-target-min: 48px;
  --touch-target-comfortable: 56px;

  /* Z-index layers */
  --z-dropdown: 100;
  --z-sticky: 200;
  --z-modal-backdrop: 900;
  --z-modal: 1000;
  --z-toast: 1100;
}

/* ============================================
   Accessibility Enhancements
   ============================================ */

/* Skip to main content link */
.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  background: var(--color-primary);
  color: white;
  padding: var(--space-sm) var(--space-md);
  z-index: 10000;
  text-decoration: none;
  font-weight: var(--font-weight-medium);
  border-radius: 0 0 var(--radius-md) 0;
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: 0;
  outline: none;
}

/* Focus visible - enhanced keyboard navigation */
*:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* Remove outline for mouse users */
*:focus:not(:focus-visible) {
  outline: none;
}

/* Screen reader only text */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* Visible on focus for skip links */
.sr-only-focusable:focus,
.sr-only-focusable:active {
  position: static;
  width: auto;
  height: auto;
  padding: inherit;
  margin: inherit;
  overflow: visible;
  clip: auto;
  white-space: normal;
}

/* Reduced motion preference */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* High contrast mode support */
@media (prefers-contrast: high) {
  :root {
    --color-border: #000000;
    --color-text-secondary: #000000;
    --color-text-muted: #333333;
  }

  .btn {
    border: 2px solid currentColor;
  }
}

/* ============================================
   Form Elements - Accessible & Touch-friendly
   ============================================ */

/* Base input styles with proper touch targets */
.form-input,
input[type="email"],
input[type="text"],
input[type="password"],
input[type="tel"],
input[type="number"],
input[type="search"],
input[type="url"],
textarea,
select {
  min-height: var(--touch-target-min);
  padding: var(--space-sm) var(--space-md);
  font-size: var(--font-size-md);
  font-family: var(--font-family);
  line-height: var(--line-height-normal);
  color: var(--color-text-primary);
  background-color: var(--color-bg-secondary);
  border: 2px solid var(--color-border);
  border-radius: var(--radius-md);
  transition: border-color var(--transition-fast),
              box-shadow var(--transition-fast),
              background-color var(--transition-fast);
  -webkit-appearance: none;
  appearance: none;
}

.form-input:hover,
input[type="email"]:hover,
input[type="text"]:hover,
input[type="password"]:hover {
  border-color: var(--color-border-dark);
}

.form-input:focus,
input[type="email"]:focus,
input[type="text"]:focus,
input[type="password"]:focus {
  outline: none;
  border-color: var(--color-primary);
  background-color: var(--color-bg-primary);
  box-shadow: var(--focus-ring);
}

/* Input states */
.form-input.is-valid,
input.success {
  border-color: var(--color-success);
  background-color: var(--color-success-bg);
}

.form-input.is-invalid,
input.error {
  border-color: var(--color-error);
  background-color: var(--color-error-bg);
}

.form-input:disabled,
input:disabled {
  background-color: var(--color-bg-tertiary);
  color: var(--color-text-disabled);
  cursor: not-allowed;
  opacity: 0.7;
}

/* Form labels */
.form-label,
label {
  display: block;
  margin-bottom: var(--space-sm);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-primary);
}

.form-label.required::after,
label.required::after {
  content: " *";
  color: var(--color-error);
}

/* Form help text */
.form-help {
  display: block;
  margin-top: var(--space-xs);
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
}

/* Form error message */
.form-error {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
  margin-top: var(--space-xs);
  font-size: var(--font-size-sm);
  color: var(--color-error);
}

.form-error::before {
  content: "";
  display: inline-block;
  width: 16px;
  height: 16px;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 20 20' fill='%23DE350B'%3E%3Cpath fill-rule='evenodd' d='M18 10a8 8 0 11-16 0 8 8 0 0116 0zm-7 4a1 1 0 11-2 0 1 1 0 012 0zm-1-9a1 1 0 00-1 1v4a1 1 0 102 0V6a1 1 0 00-1-1z' clip-rule='evenodd'/%3E%3C/svg%3E");
  background-size: contain;
  flex-shrink: 0;
}

/* OTP Input - Fixed touch targets */
.otp-input-group {
  display: flex;
  gap: var(--space-sm);
  justify-content: center;
  margin-bottom: var(--space-lg);
}

.otp-input {
  width: var(--touch-target-min);
  height: var(--touch-target-min);
  min-width: var(--touch-target-min);
  min-height: var(--touch-target-min);
  text-align: center;
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-semibold);
  border: 2px solid var(--color-border);
  border-radius: var(--radius-md);
  background-color: var(--color-bg-secondary);
  transition: all var(--transition-fast);
  -webkit-appearance: none;
  -moz-appearance: textfield;
}

.otp-input::-webkit-outer-spin-button,
.otp-input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

.otp-input:focus {
  outline: none;
  border-color: var(--color-primary);
  background-color: var(--color-bg-primary);
  box-shadow: var(--focus-ring);
}

.otp-input.filled {
  border-color: var(--color-success);
  background-color: var(--color-success-bg);
}

.otp-input.error {
  border-color: var(--color-error);
  background-color: var(--color-error-bg);
  animation: shake 0.5s ease-in-out;
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  20%, 60% { transform: translateX(-5px); }
  40%, 80% { transform: translateX(5px); }
}

/* ============================================
   Buttons - Accessible & Touch-friendly
   ============================================ */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  min-height: var(--touch-target-min);
  padding: var(--space-sm) var(--space-lg);
  font-family: var(--font-family);
  font-size: var(--font-size-md);
  font-weight: var(--font-weight-medium);
  line-height: var(--line-height-tight);
  text-decoration: none;
  color: white;
  background-color: var(--color-primary);
  border: 2px solid transparent;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  -webkit-appearance: none;
  appearance: none;
  user-select: none;
}

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

.btn:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

.btn:active:not(:disabled) {
  transform: translateY(0);
}

.btn:disabled,
.btn[aria-disabled="true"] {
  background-color: var(--color-text-disabled);
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
  opacity: 0.7;
}

/* Button variants */
.btn-secondary {
  background-color: var(--color-bg-tertiary);
  color: var(--color-text-primary);
  border-color: var(--color-border);
}

.btn-secondary:hover:not(:disabled) {
  background-color: var(--color-bg-secondary);
  border-color: var(--color-border-dark);
}

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

.btn-outline:hover:not(:disabled) {
  background-color: var(--color-primary);
  color: white;
}

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

.btn-success:hover:not(:disabled) {
  background-color: var(--color-secondary-dark);
}

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

.btn-danger:hover:not(:disabled) {
  background-color: #BF2600;
}

/* Button sizes */
.btn-sm {
  min-height: 36px;
  padding: var(--space-xs) var(--space-md);
  font-size: var(--font-size-sm);
}

.btn-lg {
  min-height: var(--touch-target-comfortable);
  padding: var(--space-md) var(--space-xl);
  font-size: var(--font-size-lg);
}

/* Full width button */
.btn-block {
  width: 100%;
}

/* ============================================
   Links - Accessible
   ============================================ */

a {
  color: var(--color-primary);
  text-decoration: underline;
  text-underline-offset: 2px;
  transition: color var(--transition-fast);
}

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

a:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: 2px;
}

/* Touch-friendly link with adequate target size */
.link-touch {
  display: inline-flex;
  align-items: center;
  min-height: var(--touch-target-min);
  padding: var(--space-sm);
  margin: calc(-1 * var(--space-sm));
}

/* ============================================
   Messages & Alerts
   ============================================ */

.message,
.alert {
  display: flex;
  align-items: flex-start;
  gap: var(--space-sm);
  padding: var(--space-md);
  border-radius: var(--radius-md);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  line-height: var(--line-height-normal);
}

.message.error,
.alert-error {
  background-color: var(--color-error-bg);
  color: var(--color-error);
  border: 1px solid var(--color-error-border);
}

.message.success,
.alert-success {
  background-color: var(--color-success-bg);
  color: #006644;
  border: 1px solid var(--color-success-border);
}

.message.warning,
.alert-warning {
  background-color: var(--color-warning-bg);
  color: #974F0C;
  border: 1px solid var(--color-warning-border);
}

.message.info,
.alert-info {
  background-color: var(--color-info-bg);
  color: var(--color-primary);
  border: 1px solid var(--color-info-border);
}

/* Live region for screen readers */
[role="alert"],
[role="status"],
[aria-live] {
  /* Ensures screen readers announce changes */
}

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

.loading-spinner {
  display: inline-block;
  width: 20px;
  height: 20px;
  border: 2px solid rgba(255, 255, 255, 0.3);
  border-radius: 50%;
  border-top-color: currentColor;
  animation: spin 0.8s linear infinite;
}

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

.loading-spinner-dark {
  border-color: rgba(0, 0, 0, 0.1);
  border-top-color: var(--color-primary);
}

/* Skeleton loading */
.skeleton {
  background: linear-gradient(90deg,
    var(--color-bg-tertiary) 0%,
    var(--color-bg-secondary) 50%,
    var(--color-bg-tertiary) 100%
  );
  background-size: 200% 100%;
  animation: skeleton-pulse 1.5s ease-in-out infinite;
  border-radius: var(--radius-sm);
}

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

/* ============================================
   Mobile Responsiveness
   ============================================ */

@media (max-width: 480px) {
  :root {
    --space-lg: 20px;
    --space-xl: 28px;
    --space-2xl: 40px;
  }

  /* Ensure OTP inputs maintain touch target size on mobile */
  .otp-input {
    width: var(--touch-target-min);
    height: var(--touch-target-min);
    font-size: var(--font-size-md);
  }

  /* Stack buttons on mobile if needed */
  .btn-group-mobile-stack {
    flex-direction: column;
  }

  /* Larger touch targets for mobile */
  .btn {
    min-height: var(--touch-target-comfortable);
  }
}

/* Tablet adjustments */
@media (min-width: 481px) and (max-width: 768px) {
  .otp-input {
    width: 52px;
    height: 52px;
  }
}

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

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

/* Margin utilities */
.mt-0 { margin-top: 0; }
.mt-1 { margin-top: var(--space-xs); }
.mt-2 { margin-top: var(--space-sm); }
.mt-3 { margin-top: var(--space-md); }
.mt-4 { margin-top: var(--space-lg); }
.mb-0 { margin-bottom: 0; }
.mb-1 { margin-bottom: var(--space-xs); }
.mb-2 { margin-bottom: var(--space-sm); }
.mb-3 { margin-bottom: var(--space-md); }
.mb-4 { margin-bottom: var(--space-lg); }

/* Display utilities */
.d-none { display: none; }
.d-block { display: block; }
.d-flex { display: flex; }
.d-inline-flex { display: inline-flex; }

/* Flex utilities */
.flex-column { flex-direction: column; }
.align-center { align-items: center; }
.justify-center { justify-content: center; }
.gap-1 { gap: var(--space-xs); }
.gap-2 { gap: var(--space-sm); }
.gap-3 { gap: var(--space-md); }