/* ===================================
   Event Registration System - Main CSS
   Design System & Shared Styles
   =================================== */

/* Import Google Fonts */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&display=swap');

/* ===================================
   CSS Custom Properties (Design Tokens)
   =================================== */
:root {
  /* Colors - Vibrant Palette */
  --color-primary: hsl(250, 85%, 60%);
  --color-primary-dark: hsl(250, 85%, 50%);
  --color-primary-light: hsl(250, 85%, 70%);
  --color-primary-alpha: hsla(250, 85%, 60%, 0.1);
  
  --color-secondary: hsl(180, 70%, 50%);
  --color-secondary-dark: hsl(180, 70%, 40%);
  --color-secondary-light: hsl(180, 70%, 60%);
  
  --color-success: hsl(142, 76%, 45%);
  --color-success-light: hsl(142, 76%, 95%);
  --color-warning: hsl(38, 92%, 50%);
  --color-warning-light: hsl(38, 92%, 95%);
  --color-error: hsl(0, 84%, 60%);
  --color-error-light: hsl(0, 84%, 95%);
  --color-info: hsl(217, 91%, 60%);
  --color-info-light: hsl(217, 91%, 95%);
  
  /* Neutrals */
  --color-bg: hsl(0, 0%, 100%);
  --color-bg-secondary: hsl(240, 20%, 98%);
  --color-bg-tertiary: hsl(240, 15%, 95%);
  --color-surface: hsl(0, 0%, 100%);
  --color-surface-elevated: hsl(0, 0%, 100%);
  
  --color-text: hsl(240, 15%, 15%);
  --color-text-secondary: hsl(240, 10%, 45%);
  --color-text-tertiary: hsl(240, 8%, 65%);
  --color-text-inverse: hsl(0, 0%, 100%);
  
  --color-border: hsl(240, 15%, 90%);
  --color-border-light: hsl(240, 10%, 95%);
  --color-border-focus: var(--color-primary);
  
  /* 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-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
  
  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;
  
  /* Border Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;
  
  /* Typography */
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-size-xs: 0.75rem;
  --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;
  
  --font-weight-light: 300;
  --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;
  
  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
  
  /* Z-index */
  --z-dropdown: 1000;
  --z-sticky: 1020;
  --z-fixed: 1030;
  --z-modal-backdrop: 1040;
  --z-modal: 1050;
  --z-popover: 1060;
  --z-tooltip: 1070;
}

/* Dark Mode Support */
@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: hsl(240, 15%, 10%);
    --color-bg-secondary: hsl(240, 15%, 12%);
    --color-bg-tertiary: hsl(240, 15%, 15%);
    --color-surface: hsl(240, 15%, 13%);
    --color-surface-elevated: hsl(240, 15%, 16%);
    
    --color-text: hsl(0, 0%, 95%);
    --color-text-secondary: hsl(240, 5%, 70%);
    --color-text-tertiary: hsl(240, 5%, 55%);
    
    --color-border: hsl(240, 10%, 25%);
    --color-border-light: hsl(240, 10%, 20%);
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -1px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5), 0 4px 6px -2px rgba(0, 0, 0, 0.3);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.6), 0 10px 10px -5px rgba(0, 0, 0, 0.4);
  }
}

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

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-normal);
  line-height: var(--line-height-normal);
  color: var(--color-text);
  background-color: var(--color-bg);
  min-height: 100vh;
}

/* ===================================
   Typography
   =================================== */
h1, h2, h3, h4, h5, h6 {
  font-weight: var(--font-weight-bold);
  line-height: var(--line-height-tight);
  margin-bottom: var(--space-md);
  color: var(--color-text);
}

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

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

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

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

/* ===================================
   Layout Components
   =================================== */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.container-sm {
  max-width: 640px;
}

.container-md {
  max-width: 768px;
}

.container-lg {
  max-width: 1024px;
}

.section {
  padding: var(--space-3xl) 0;
}

.grid {
  display: grid;
  gap: var(--space-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: 768px) {
  .grid-2, .grid-3, .grid-4 {
    grid-template-columns: 1fr;
  }
}

.flex {
  display: flex;
  gap: var(--space-md);
}

.flex-center {
  display: flex;
  align-items: center;
  justify-content: center;
}

.flex-between {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.flex-column {
  flex-direction: column;
}

/* ===================================
   Card Component
   =================================== */
.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  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(--space-lg);
  padding-bottom: var(--space-lg);
  border-bottom: 1px solid var(--color-border-light);
}

.card-title {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--space-xs);
}

.card-subtitle {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
}

.card-body {
  margin-bottom: var(--space-lg);
}

.card-footer {
  margin-top: var(--space-lg);
  padding-top: var(--space-lg);
  border-top: 1px solid var(--color-border-light);
}

/* ===================================
   Button Component
   =================================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: 0.625rem 1.25rem;
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-medium);
  line-height: 1.5;
  text-align: center;
  text-decoration: none;
  white-space: nowrap;
  border: 1px solid transparent;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  user-select: none;
}

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

.btn-primary {
  color: var(--color-text-inverse);
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
  box-shadow: 0 4px 12px var(--color-primary-alpha);
}

.btn-primary:hover {
  background: linear-gradient(135deg, var(--color-primary-dark) 0%, var(--color-primary) 100%);
  box-shadow: 0 6px 16px var(--color-primary-alpha);
  transform: translateY(-1px);
}

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

.btn-secondary:hover {
  background: var(--color-bg-tertiary);
  border-color: var(--color-border);
}

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

.btn-success:hover {
  background: hsl(142, 76%, 40%);
  transform: translateY(-1px);
}

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

.btn-danger:hover {
  background: hsl(0, 84%, 55%);
  transform: translateY(-1px);
}

.btn-ghost {
  color: var(--color-text);
  background: transparent;
  border-color: transparent;
}

.btn-ghost:hover {
  background: var(--color-bg-secondary);
}

.btn-sm {
  padding: 0.375rem 0.875rem;
  font-size: var(--font-size-sm);
}

.btn-lg {
  padding: 0.875rem 1.75rem;
  font-size: var(--font-size-lg);
}

.btn-block {
  display: flex;
  width: 100%;
}

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

.form-label {
  display: block;
  margin-bottom: var(--space-sm);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text);
}

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

.form-input,
.form-select,
.form-textarea {
  display: block;
  width: 100%;
  padding: 0.625rem 0.875rem;
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: 1.5;
  color: var(--color-text);
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  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-border-focus);
  box-shadow: 0 0 0 3px var(--color-primary-alpha);
}

.form-input::placeholder {
  color: var(--color-text-tertiary);
}

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

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

.form-help {
  display: block;
  margin-top: var(--space-sm);
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
}

.form-checkbox,
.form-radio {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  margin-bottom: var(--space-sm);
}

.form-checkbox input,
.form-radio input {
  width: 1.125rem;
  height: 1.125rem;
  cursor: pointer;
}

/* ===================================
   Alert Component
   =================================== */
.alert {
  padding: var(--space-md) var(--space-lg);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-lg);
  border-left: 4px solid;
}

.alert-success {
  background: var(--color-success-light);
  border-color: var(--color-success);
  color: hsl(142, 76%, 25%);
}

.alert-error {
  background: var(--color-error-light);
  border-color: var(--color-error);
  color: hsl(0, 84%, 35%);
}

.alert-warning {
  background: var(--color-warning-light);
  border-color: var(--color-warning);
  color: hsl(38, 92%, 25%);
}

.alert-info {
  background: var(--color-info-light);
  border-color: var(--color-info);
  color: hsl(217, 91%, 30%);
}

/* ===================================
   Modal Component
   =================================== */
.modal-backdrop {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.5);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: var(--z-modal-backdrop);
  animation: fadeIn var(--transition-base);
}

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

.modal-header {
  padding: var(--space-xl);
  border-bottom: 1px solid var(--color-border-light);
}

.modal-title {
  font-size: var(--font-size-2xl);
  font-weight: var(--font-weight-semibold);
}

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

.modal-footer {
  padding: var(--space-xl);
  border-top: 1px solid var(--color-border-light);
  display: flex;
  gap: var(--space-md);
  justify-content: flex-end;
}

/* ===================================
   Badge Component
   =================================== */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 0.25rem 0.625rem;
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-medium);
  line-height: 1;
  border-radius: var(--radius-full);
}

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

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

.badge-warning {
  background: var(--color-warning-light);
  color: hsl(38, 92%, 35%);
}

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

/* ===================================
   Loading States
   =================================== */
.spinner {
  display: inline-block;
  width: 1.5rem;
  height: 1.5rem;
  border: 3px solid var(--color-border);
  border-top-color: var(--color-primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

.skeleton {
  background: linear-gradient(
    90deg,
    var(--color-bg-secondary) 0%,
    var(--color-bg-tertiary) 50%,
    var(--color-bg-secondary) 100%
  );
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: var(--radius-md);
}

.skeleton-text {
  height: 1rem;
  margin-bottom: var(--space-sm);
}

.skeleton-title {
  height: 2rem;
  width: 60%;
  margin-bottom: var(--space-md);
}

/* ===================================
   Utility Classes
   =================================== */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

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

.font-light { font-weight: var(--font-weight-light); }
.font-normal { font-weight: var(--font-weight-normal); }
.font-medium { font-weight: var(--font-weight-medium); }
.font-semibold { font-weight: var(--font-weight-semibold); }
.font-bold { font-weight: var(--font-weight-bold); }

.mt-0 { margin-top: 0; }
.mt-sm { margin-top: var(--space-sm); }
.mt-md { margin-top: var(--space-md); }
.mt-lg { margin-top: var(--space-lg); }
.mt-xl { margin-top: var(--space-xl); }

.mb-0 { margin-bottom: 0; }
.mb-sm { margin-bottom: var(--space-sm); }
.mb-md { margin-bottom: var(--space-md); }
.mb-lg { margin-bottom: var(--space-lg); }
.mb-xl { margin-bottom: var(--space-xl); }

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

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

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

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

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

/* ===================================
   Responsive Utilities
   =================================== */
@media (max-width: 640px) {
  .hide-mobile { display: none; }
}

@media (min-width: 641px) {
  .show-mobile { display: none; }
}