/* ============================================
   Premium Design System - A11y Patterns
   ============================================ */

/* Font Face Declarations */
@font-face {
  font-family: 'GeistPixel';
  src: url('fonts/GeistPixel-Square.woff2') format('woff2'),
       url('fonts/GeistPixel-Square.ttf') format('truetype'),
       url('fonts/GeistPixel-Square.otf') format('opentype');
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}

/* CSS Variables */
:root {
  color-scheme: light;

  /* === Colors === */
  /* Backgrounds */
  --color-background: #fafafa;
  --color-surface: #ffffff;
  --color-surface-elevated: #ffffff;
  --color-surface-subtle: #f5f5f5;

  /* Text */
  --color-text: #1a1a1a;
  --color-text-secondary: #525252;
  --color-text-tertiary: #737373;
  --color-text-inverse: #fafafa;

  /* Borders */
  --color-border: #e5e5e5;
  --color-border-subtle: #f0f0f0;
  --color-border-strong: #d4d4d4;

  /* Accent - Premium Emerald */
  --color-accent: #059669;
  --color-accent-hover: #047857;
  --color-accent-subtle: #d1fae5;
  --color-accent-text: #064e3b;

  /* Status Colors */
  --color-success: #059669;
  --color-success-subtle: #d1fae5;
  --color-warning: #d97706;
  --color-warning-subtle: #fef3c7;
  --color-error: #dc2626;
  --color-error-subtle: #fee2e2;

  /* WCAG Level Colors */
  --wcag-a-bg: #dbeafe;
  --wcag-a-text: #1e40af;
  --wcag-aa-bg: #d1fae5;
  --wcag-aa-text: #065f46;
  --wcag-aaa-bg: #fef3c7;
  --wcag-aaa-text: #92400e;

  /* === Typography === */
  --font-family: 'GeistPixel', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-family-mono: 'GeistPixel', 'SF Mono', 'Fira Code', 'Fira Mono', 'Roboto 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: 2rem;
  --text-4xl: 2.5rem;

  /* Font Weights */
  --font-normal: 400;
  --font-medium: 500;
  --font-semibold: 600;
  --font-bold: 700;

  /* Line Heights */
  --leading-tight: 1.25;
  --leading-normal: 1.6;
  --leading-relaxed: 1.75;

  /* Letter Spacing */
  --tracking-tight: -0.02em;
  --tracking-normal: 0;
  --tracking-wide: 0.025em;

  /* === Spacing === */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;

  /* === Border Radius === */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-xl: 20px;
  --radius-full: 9999px;

  /* === Shadows === */
  --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.04);
  --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.04), 0 1px 2px rgba(0, 0, 0, 0.02);
  --shadow-md: 0 4px 8px rgba(0, 0, 0, 0.04), 0 2px 4px rgba(0, 0, 0, 0.02);
  --shadow-lg: 0 12px 24px rgba(0, 0, 0, 0.06), 0 4px 8px rgba(0, 0, 0, 0.04);
  --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.08), 0 8px 16px rgba(0, 0, 0, 0.04);

  /* === Transitions === */
  --transition-fast: 150ms ease-out;
  --transition-base: 200ms ease-out;
  --transition-slow: 300ms ease-out;
  --transition-spring: 400ms cubic-bezier(0.175, 0.885, 0.32, 1.275);

  /* === Z-Index === */
  --z-dropdown: 100;
  --z-sticky: 200;
  --z-fixed: 300;
  --z-modal: 400;
  --z-popover: 500;
  --z-tooltip: 600;

  /* === Layout === */
  --container-max: 1512px;
  --header-height: 72px;
}

/* ============================================
   Dark Mode
   ============================================ */
@media (prefers-color-scheme: dark) {
  :root {
    color-scheme: dark;

    /* Backgrounds */
    --color-background: #0a0a0a;
    --color-surface: #141414;
    --color-surface-elevated: #1a1a1a;
    --color-surface-subtle: #0f0f0f;

    /* Text */
    --color-text: #fafafa;
    --color-text-secondary: #a3a3a3;
    --color-text-tertiary: #737373;
    --color-text-inverse: #1a1a1a;

    /* Borders */
    --color-border: #262626;
    --color-border-subtle: #1f1f1f;
    --color-border-strong: #404040;

    /* Accent - Premium Emerald (Dark Mode) */
    --color-accent: #10b981;
    --color-accent-hover: #34d399;
    --color-accent-subtle: #064e3b;
    --color-accent-text: #d1fae5;

    /* Status Colors (Dark Mode) */
    --color-success: #10b981;
    --color-success-subtle: #064e3b;
    --color-warning: #f59e0b;
    --color-warning-subtle: #78350f;
    --color-error: #ef4444;
    --color-error-subtle: #7f1d1d;

    /* WCAG Level Colors (Dark Mode) */
    --wcag-a-bg: #1e3a5f;
    --wcag-a-text: #93c5fd;
    --wcag-aa-bg: #064e3b;
    --wcag-aa-text: #6ee7b7;
    --wcag-aaa-bg: #78350f;
    --wcag-aaa-text: #fcd34d;

    /* Shadows (Dark Mode) */
    --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.3), 0 1px 2px rgba(0, 0, 0, 0.2);
    --shadow-md: 0 4px 8px rgba(0, 0, 0, 0.3), 0 2px 4px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 12px 24px rgba(0, 0, 0, 0.4), 0 4px 8px rgba(0, 0, 0, 0.3);
    --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.5), 0 8px 16px rgba(0, 0, 0, 0.3);
  }
}

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

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

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

/* ============================================
   Container
   ============================================ */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-6);
}

@media (max-width: 768px) {
  .container {
    padding: 0 var(--space-4);
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 var(--space-3);
  }
}

/* ============================================
   Site Header
   ============================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  background-color: rgba(250, 250, 250, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  padding: var(--space-5) 0;
  transition: background-color var(--transition-base), border-color var(--transition-base);
}

@media (max-width: 640px) {
  .site-header {
    padding: var(--space-4) 0;
  }
}

@media (prefers-color-scheme: dark) {
  .site-header {
    background-color: rgba(10, 10, 10, 0.85);
  }
}

.site-header .container {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

@media (max-width: 640px) {
  .site-header .container {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-4);
  }
}

.site-title {
  font-size: var(--text-2xl);
  font-weight: var(--font-bold);
  letter-spacing: var(--tracking-tight);
  line-height: var(--leading-tight);
  display: flex;
  align-items: center;
  gap: var(--space-3);
  color: var(--color-text);
  text-decoration: none;
}

@media (max-width: 640px) {
  .site-title {
    font-size: var(--text-xl);
  }
}

.site-title__icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  background-color: var(--color-accent-subtle);
  border-radius: var(--radius-md);
  color: var(--color-accent);
  transition: transform var(--transition-spring);
}

@media (max-width: 640px) {
  .site-title__icon {
    width: 36px;
    height: 36px;
  }
}

.site-title:hover .site-title__icon {
  transform: scale(1.05);
}

.site-tagline {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  line-height: var(--leading-normal);
}

@media (max-width: 640px) {
  .site-tagline {
    text-align: right;
    font-size: var(--text-xs);
  }
}

/* Material Symbols */
.material-symbols-outlined {
  font-size: inherit;
  line-height: 1;
  vertical-align: middle;
  user-select: none;
}

/* ============================================
   Filters Section
   ============================================ */
.filters {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  padding: var(--space-6);
  margin-top: var(--space-10);
  margin-bottom: var(--space-8);
  box-shadow: var(--shadow-sm);
  transition: border-color var(--transition-base);
}

@media (max-width: 640px) {
  .filters {
    padding: var(--space-4);
    margin-top: var(--space-6);
    margin-bottom: var(--space-6);
  }
}

.filters:hover {
  border-color: var(--color-border-strong);
}

.filters__header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-5);
  flex-wrap: wrap;
  gap: var(--space-3);
}

@media (max-width: 640px) {
  .filters__header {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--space-4);
  }
}

.filters__title {
  font-size: var(--text-lg);
  font-weight: var(--font-semibold);
  letter-spacing: var(--tracking-tight);
  color: var(--color-text);
}

.filters__group {
  display: flex;
  gap: var(--space-4);
  flex-wrap: wrap;
}

@media (max-width: 640px) {
  .filters__group {
    gap: var(--space-3);
    width: 100%;
  }
}

.filter-label {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  flex: 1;
  min-width: 200px;
}

@media (max-width: 640px) {
  .filter-label {
    min-width: 100%;
  }
}

.filter-label__text {
  font-size: var(--text-xs);
  font-weight: var(--font-semibold);
  text-transform: uppercase;
  letter-spacing: var(--tracking-wide);
  color: var(--color-text-tertiary);
}

.filter-select {
  appearance: none;
  -webkit-appearance: none;
  width: 100%;
  padding: var(--space-3) var(--space-4);
  padding-right: var(--space-10);
  font-family: var(--font-family);
  font-size: var(--text-sm);
  font-weight: var(--font-medium);
  color: var(--color-text);
  background-color: var(--color-surface);
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='%23737373' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right var(--space-3) center;
  background-size: 16px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.filter-select:hover {
  border-color: var(--color-border-strong);
}

.filter-select:focus {
  outline: none;
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px var(--color-accent-subtle);
}

.filters__results {
  margin-top: var(--space-4);
  padding-top: var(--space-4);
  border-top: 1px solid var(--color-border-subtle);
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
}

/* ============================================
   Patterns Grid
   ============================================ */
.patterns-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-4);
  margin-bottom: var(--space-12);
}

@media (min-width: 640px) {
  .patterns-grid {
    gap: var(--space-5);
  }
}

/* Tablet: 2 columns */
@media (min-width: 640px) {
  .patterns-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* Desktop: 3 columns */
@media (min-width: 1024px) {
  .patterns-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-6);
  }
}

/* Larger screens: 4 columns */
@media (min-width: 1440px) {
  .patterns-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

/* ============================================
   Pattern Card
   ============================================ */
.pattern-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  transition: transform var(--transition-base), box-shadow var(--transition-base), border-color var(--transition-base);
  position: relative;
  overflow: hidden;
}

@media (max-width: 640px) {
  .pattern-card {
    padding: var(--space-4);
  }
}

.pattern-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--color-accent), var(--color-accent-hover));
  opacity: 0;
  transition: opacity var(--transition-base);
}

.pattern-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--color-border-strong);
}

.pattern-card:hover::before {
  opacity: 1;
}

.pattern-card__header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: var(--space-4);
  gap: var(--space-3);
}

.pattern-card__category {
  font-size: var(--text-xs);
  font-weight: var(--font-semibold);
  text-transform: uppercase;
  letter-spacing: var(--tracking-wide);
  color: var(--color-text-tertiary);
  padding: var(--space-1) var(--space-3);
  background-color: var(--color-surface-subtle);
  border-radius: var(--radius-full);
}

.pattern-card__wcag {
  font-size: var(--text-xs);
  font-weight: var(--font-semibold);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
}

.pattern-card__wcag--A {
  background-color: var(--wcag-a-bg);
  color: var(--wcag-a-text);
}

.pattern-card__wcag--AA {
  background-color: var(--wcag-aa-bg);
  color: var(--wcag-aa-text);
}

.pattern-card__wcag--AAA {
  background-color: var(--wcag-aaa-bg);
  color: var(--wcag-aaa-text);
}

.pattern-card__title {
  font-size: var(--text-xl);
  font-weight: var(--font-semibold);
  letter-spacing: var(--tracking-tight);
  line-height: var(--leading-tight);
  margin-bottom: var(--space-3);
  color: var(--color-text);
}

.pattern-card__description {
  font-size: var(--text-sm);
  line-height: var(--leading-relaxed);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-6);
  flex-grow: 1;
}

.pattern-card__footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: var(--space-4);
  border-top: 1px solid var(--color-border-subtle);
  gap: var(--space-4);
}

.pattern-card__criterion {
  font-size: var(--text-xs);
  font-family: var(--font-family-mono);
  color: var(--color-text-tertiary);
  background-color: var(--color-surface-subtle);
  padding: var(--space-1) var(--space-2);
  border-radius: var(--radius-sm);
}

.pattern-card__link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  background-color: var(--color-accent);
  color: var(--color-text-inverse);
  text-decoration: none;
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: var(--font-semibold);
  transition: background-color var(--transition-fast), transform var(--transition-fast);
}

.pattern-card__link:hover {
  background-color: var(--color-accent-hover);
  transform: translateY(-1px);
}

.pattern-card__link:focus {
  outline: none;
  box-shadow: 0 0 0 3px var(--color-accent-subtle);
}

/* ============================================
   Empty State
   ============================================ */
.empty-state {
  grid-column: 1 / -1;
  text-align: center;
  padding: var(--space-16) var(--space-8);
  color: var(--color-text-secondary);
}

.empty-state__icon {
  margin-bottom: var(--space-4);
  color: var(--color-text-tertiary);
}

.empty-state__icon .material-symbols-outlined {
  font-size: 3rem;
}

.empty-state__title {
  font-size: var(--text-xl);
  font-weight: var(--font-semibold);
  margin-bottom: var(--space-2);
  color: var(--color-text);
}

.empty-state__description {
  font-size: var(--text-base);
  max-width: 400px;
  margin: 0 auto;
}

/* ============================================
   Site Footer
   ============================================ */
.site-footer {
  background-color: var(--color-surface);
  border-top: 1px solid var(--color-border);
  padding: var(--space-10) 0;
  margin-top: var(--space-16);
}

.site-footer__text {
  text-align: center;
  color: var(--color-text-secondary);
  font-size: var(--text-sm);
  margin-bottom: var(--space-3);
  line-height: var(--leading-relaxed);
}

.site-footer__text code,
.pattern-card__description code,
.key-rules__item code{
  font-family: var(--font-family-mono);
  font-size: var(--text-xs);
  background-color: var(--color-surface-subtle);
  padding: var(--space-1) var(--space-2);
  border-radius: var(--radius-sm);
  color: var(--color-accent);
}

.github-link {
  display: flex;
  justify-content: center;
  margin-top: var(--space-4);
}

.github-link a {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  background-color: var(--color-surface-subtle);
  color: var(--color-text);
  text-decoration: none;
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: var(--font-medium);
  transition: background-color var(--transition-fast), color var(--transition-fast);
}

.github-link a:hover {
  background-color: var(--color-border-subtle);
  color: var(--color-accent);
}

.github-link a:focus {
  outline: none;
  box-shadow: 0 0 0 3px var(--color-accent-subtle);
}

.github-logo {
  width: 20px;
  height: 20px;
  color: currentColor;
}

.github-logo svg {
  width: 100%;
  height: 100%;
}

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 639px) {
  .site-title {
    font-size: var(--text-xl);
  }

  .site-title__icon {
    width: 36px;
    height: 36px;
  }

  .site-tagline {
    text-align: left;
  }

  .filters {
    padding: var(--space-5);
  }

  .filters__group {
    flex-direction: column;
  }

  .filter-label {
    min-width: 100%;
  }

  .pattern-card__footer {
    flex-direction: column;
    align-items: stretch;
  }

  .pattern-card__link {
    justify-content: center;
  }
}

/* ============================================
   Loading Animation
   ============================================ */
@keyframes shimmer {
  0% {
    background-position: -200% 0;
  }
  100% {
    background-position: 200% 0;
  }
}

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

/* ============================================
   Focus Styles for Accessibility
   ============================================ */
:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

/* Skip link for keyboard users */
.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-6);
  padding: var(--space-3) var(--space-5);
  background-color: var(--color-accent);
  color: var(--color-text-inverse);
  text-decoration: none;
  border-radius: var(--radius-md);
  font-weight: var(--font-semibold);
  z-index: var(--z-tooltip);
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: var(--space-6);
}