/* ==========================================================================
   a11ybot -- Design Tokens
   ========================================================================== */

:root {
  /* Palette -- clean, professional, high contrast */
  --color-primary: #1a56db;       /* Strong blue -- trust, tech */
  --color-primary-dark: #1342a8;
  --color-primary-light: #e8effc;
  --color-accent: #059669;        /* Green -- success, good examples */
  --color-danger: #dc2626;        /* Red -- errors, bad examples */
  --color-text: #111827;          /* Near-black */
  --color-text-muted: #6b7280;
  --color-bg: #ffffff;
  --color-bg-alt: #f9fafb;
  --color-bg-dark: #111827;
  --color-border: #e5e7eb;

  /* Typography */
  --font-body: "Inter", "Segoe UI", system-ui, -apple-system, sans-serif;
  --font-heading: "Inter", "Segoe UI", system-ui, -apple-system, sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", ui-monospace, monospace;

  --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;

  /* 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;

  /* Layout */
  --max-width: 1200px;
  --sidebar-width: 260px;

  /* Effects */
  --radius: 0.5rem;
  --radius-sm: 0.25rem;
  --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 25px rgba(0, 0, 0, 0.1);
  --focus-ring: 0 0 0 3px rgba(26, 86, 219, 0.4);

  /* Transitions */
  --transition: 150ms ease;
}

/* ==========================================================================
   Reset
   ========================================================================== */

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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

body {
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

img, picture, video, canvas, svg {
  display: block;
  max-width: 100%;
}

input, button, textarea, select {
  font: inherit;
}

a {
  color: var(--color-primary);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 2px;
}

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

ul[role="list"],
ol[role="list"] {
  list-style: none;
}

/* ==========================================================================
   Focus styles -- accessibility first
   ========================================================================== */

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

/* ==========================================================================
   Skip link
   ========================================================================== */

.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-md);
  z-index: 1000;
  padding: var(--space-sm) var(--space-md);
  background: var(--color-primary);
  color: #fff;
  font-weight: 600;
  text-decoration: none;
  border-radius: var(--radius-sm);
}

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

/* ==========================================================================
   Header
   ========================================================================== */

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-md) var(--space-lg);
}

.site-logo {
  text-decoration: none;
  font-size: var(--text-xl);
  font-weight: 800;
  letter-spacing: -0.02em;
}

.logo-mark {
  color: var(--color-text);
}

.logo-accent {
  color: var(--color-primary);
}

.nav-list {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
}

.nav-list a {
  color: var(--color-text);
  text-decoration: none;
  font-size: var(--text-sm);
  font-weight: 500;
}

.nav-list a:hover {
  color: var(--color-primary);
}

.nav-list a[aria-current="page"] {
  color: var(--color-primary);
  font-weight: 600;
}

/* Mobile nav toggle */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-sm);
}

.nav-toggle-icon {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-text);
  position: relative;
}

.nav-toggle-icon::before,
.nav-toggle-icon::after {
  content: "";
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-text);
  position: absolute;
  left: 0;
}

.nav-toggle-icon::before { top: -7px; }
.nav-toggle-icon::after { top: 7px; }

/* ==========================================================================
   Buttons
   ========================================================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-sm) var(--space-lg);
  font-size: var(--text-sm);
  font-weight: 600;
  text-decoration: none;
  border-radius: var(--radius);
  border: 2px solid transparent;
  cursor: pointer;
  transition: all var(--transition);
}

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

.btn-primary:hover {
  background: var(--color-primary-dark);
  color: #fff;
}

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

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

.btn-sm {
  padding: var(--space-xs) var(--space-md);
  font-size: var(--text-xs);
}

.btn-lg {
  padding: var(--space-md) var(--space-xl);
  font-size: var(--text-base);
}

/* ==========================================================================
   Footer
   ========================================================================== */

.site-footer {
  background: var(--color-bg-dark);
  color: #e5e7eb;
  padding: var(--space-3xl) var(--space-lg) var(--space-lg);
}

.footer-inner {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: var(--space-2xl);
  max-width: var(--max-width);
  margin: 0 auto;
}

.footer-logo {
  font-size: var(--text-xl);
  font-weight: 800;
  letter-spacing: -0.02em;
}

.footer-logo .logo-mark { color: #fff; }
.footer-logo .logo-accent { color: #93bbfd; }

.footer-tagline {
  color: var(--color-text-muted);
  font-size: var(--text-sm);
  margin-top: var(--space-xs);
}

.footer-nav ul {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.footer-nav a {
  color: #e5e7eb;
  text-decoration: none;
  font-size: var(--text-sm);
}

.footer-nav a:hover {
  color: #fff;
}

.footer-contact {
  font-size: var(--text-sm);
}

.footer-contact a {
  color: #93bbfd;
}

.footer-legal {
  max-width: var(--max-width);
  margin: var(--space-2xl) auto 0;
  padding-top: var(--space-lg);
  border-top: 1px solid #374151;
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}

/* ==========================================================================
   Page content
   ========================================================================== */

.page-content {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-2xl) var(--space-lg);
}

/* ==========================================================================
   Hero
   ========================================================================== */

.hero {
  padding: var(--space-3xl) var(--space-lg);
  text-align: center;
}

.hero-inner {
  max-width: 800px;
  margin: 0 auto;
}

.hero h1 {
  font-size: var(--text-4xl);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.03em;
  margin-bottom: var(--space-lg);
}

.hero p {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  margin-bottom: var(--space-xl);
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.hero-actions {
  display: flex;
  gap: var(--space-md);
  justify-content: center;
  flex-wrap: wrap;
}

/* ==========================================================================
   Feature grid
   ========================================================================== */

.features {
  padding: var(--space-3xl) var(--space-lg);
  background: var(--color-bg-alt);
}

.features-inner {
  max-width: var(--max-width);
  margin: 0 auto;
}

.features h2 {
  text-align: center;
  font-size: var(--text-3xl);
  font-weight: 700;
  margin-bottom: var(--space-2xl);
}

.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-xl);
}

.feature-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-xl);
}

.feature-card h3 {
  font-size: var(--text-lg);
  font-weight: 600;
  margin-bottom: var(--space-sm);
}

.feature-card p {
  color: var(--color-text-muted);
  font-size: var(--text-sm);
}

/* ==========================================================================
   Learn sidebar
   ========================================================================== */

.learn-sidebar {
  position: sticky;
  top: 80px;
  align-self: start;
  padding: var(--space-md);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-bg);
  max-height: calc(100vh - 100px);
  overflow-y: auto;
}

.learn-sidebar details {
  margin-bottom: var(--space-sm);
}

.learn-sidebar summary {
  font-weight: 600;
  font-size: var(--text-sm);
  cursor: pointer;
  padding: var(--space-xs) 0;
  list-style: none;
}

.learn-sidebar summary::before {
  content: "\25B6";
  display: inline-block;
  margin-right: var(--space-sm);
  font-size: var(--text-xs);
  transition: transform var(--transition);
}

.learn-sidebar details[open] > summary::before {
  transform: rotate(90deg);
}

.learn-sidebar ul {
  padding-left: var(--space-lg);
}

.learn-sidebar li {
  margin-bottom: var(--space-xs);
}

.learn-sidebar a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: var(--text-sm);
}

.learn-sidebar a:hover {
  color: var(--color-primary);
}

.learn-sidebar a[aria-current="page"] {
  color: var(--color-primary);
  font-weight: 600;
}

/* ==========================================================================
   Criterion layout
   ========================================================================== */

.criterion-layout {
  display: grid;
  grid-template-columns: var(--sidebar-width) 1fr;
  gap: var(--space-2xl);
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-2xl) var(--space-lg);
}

.criterion-header {
  margin-bottom: var(--space-2xl);
}

.breadcrumb {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-md);
}

.breadcrumb a {
  color: var(--color-text-muted);
}

.breadcrumb span[aria-hidden] {
  margin: 0 var(--space-xs);
}

.level-badge {
  display: inline-block;
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-sm);
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  background: var(--color-primary-light);
  color: var(--color-primary-dark);
  margin-bottom: var(--space-sm);
}

.criterion-stat {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-md);
}

.criterion-header h1 {
  font-size: var(--text-3xl);
  font-weight: 700;
  line-height: 1.2;
}

.criterion-content section {
  margin-bottom: var(--space-2xl);
}

.criterion-content h2 {
  font-size: var(--text-xl);
  font-weight: 600;
  margin-bottom: var(--space-md);
}

.criterion-content p,
.criterion-content li {
  line-height: 1.7;
  margin-bottom: var(--space-sm);
}

.criterion-content ul,
.criterion-content ol {
  padding-left: var(--space-xl);
}

/* ==========================================================================
   Example panels
   ========================================================================== */

.examples-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-lg);
}

.example-panel {
  border: 2px solid var(--color-border);
  border-radius: var(--radius);
  overflow: hidden;
}

.example-panel--good {
  border-color: var(--color-accent);
}

.example-panel--bad {
  border-color: var(--color-danger);
}

.example-panel-header {
  padding: var(--space-sm) var(--space-md);
  font-size: var(--text-sm);
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.example-panel--good .example-panel-header {
  background: #ecfdf5;
  color: #065f46;
}

.example-panel--bad .example-panel-header {
  background: #fef2f2;
  color: #991b1b;
}

.example-panel-body {
  padding: var(--space-md);
}

.example-panel-body iframe {
  width: 100%;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
}

.code-toggle {
  display: block;
  margin-top: var(--space-sm);
  background: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: var(--space-xs) var(--space-sm);
  font-size: var(--text-xs);
  font-family: var(--font-mono);
  cursor: pointer;
  color: var(--color-text-muted);
}

.code-toggle:hover {
  background: var(--color-bg-alt);
}

.code-block {
  display: none;
  margin-top: var(--space-sm);
  padding: var(--space-md);
  background: var(--color-bg-dark);
  color: #e5e7eb;
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  line-height: 1.6;
  overflow-x: auto;
  white-space: pre;
}

.code-block.is-visible {
  display: block;
}

/* ==========================================================================
   Criterion nav (prev/next)
   ========================================================================== */

.criterion-nav {
  display: flex;
  justify-content: space-between;
  gap: var(--space-lg);
  padding-top: var(--space-2xl);
  border-top: 1px solid var(--color-border);
  margin-top: var(--space-2xl);
}

.criterion-nav a {
  text-decoration: none;
  padding: var(--space-md);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  flex: 1;
  transition: all var(--transition);
}

.criterion-nav a:hover {
  border-color: var(--color-primary);
  box-shadow: var(--shadow-sm);
}

.criterion-nav-next {
  text-align: right;
}

.criterion-nav-label {
  display: block;
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--space-xs);
}

.criterion-nav-title {
  font-weight: 600;
  font-size: var(--text-sm);
  color: var(--color-primary);
}

/* ==========================================================================
   Learn hub index
   ========================================================================== */

.learn-layout {
  display: grid;
  grid-template-columns: var(--sidebar-width) 1fr;
  gap: var(--space-2xl);
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-2xl) var(--space-lg);
}

.learn-header {
  margin-bottom: var(--space-2xl);
}

.learn-header h1 {
  font-size: var(--text-3xl);
  font-weight: 700;
  margin-bottom: var(--space-sm);
}

.learn-header p {
  color: var(--color-text-muted);
  font-size: var(--text-lg);
}

.filter-controls {
  display: flex;
  gap: var(--space-sm);
  margin-bottom: var(--space-xl);
}

.filter-btn {
  padding: var(--space-xs) var(--space-md);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-bg);
  font-size: var(--text-sm);
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition);
}

.filter-btn:hover {
  border-color: var(--color-primary);
}

.filter-btn[aria-pressed="true"] {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

.criterion-list {
  margin-bottom: var(--space-2xl);
}

.criterion-list h2 {
  font-size: var(--text-xl);
  font-weight: 600;
  margin-bottom: var(--space-md);
  padding-bottom: var(--space-sm);
  border-bottom: 2px solid var(--color-border);
}

.criterion-item {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  margin-bottom: var(--space-sm);
  text-decoration: none;
  color: var(--color-text);
  transition: all var(--transition);
}

.criterion-item:hover {
  border-color: var(--color-primary);
  box-shadow: var(--shadow-sm);
}

.criterion-id {
  font-weight: 700;
  font-size: var(--text-sm);
  color: var(--color-primary);
  min-width: 3rem;
}

.criterion-name {
  flex: 1;
  font-weight: 500;
}

.criterion-level {
  font-size: var(--text-xs);
  font-weight: 700;
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-sm);
  background: var(--color-primary-light);
  color: var(--color-primary-dark);
}

.criterion-stat-inline {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}

/* ==========================================================================
   Pricing
   ========================================================================== */

.pricing-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-xl);
  margin-top: var(--space-2xl);
}

.pricing-card {
  border: 2px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-xl);
}

.pricing-card--featured {
  border-color: var(--color-primary);
}

.pricing-card h3 {
  font-size: var(--text-xl);
  font-weight: 600;
  margin-bottom: var(--space-sm);
}

.pricing-price {
  font-size: var(--text-3xl);
  font-weight: 800;
  color: var(--color-primary);
  margin-bottom: var(--space-md);
}

.pricing-card ul {
  padding-left: var(--space-lg);
  margin-bottom: var(--space-lg);
}

.pricing-card li {
  font-size: var(--text-sm);
  margin-bottom: var(--space-sm);
}

/* ==========================================================================
   Responsive
   ========================================================================== */

@media (max-width: 768px) {
  .nav-toggle {
    display: block;
  }

  .nav-list {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    padding: var(--space-md) var(--space-lg);
    flex-direction: column;
    gap: var(--space-md);
    box-shadow: var(--shadow-md);
  }

  .nav-list.is-open {
    display: flex;
  }

  .criterion-layout,
  .learn-layout {
    grid-template-columns: 1fr;
  }

  .learn-sidebar {
    position: static;
    max-height: none;
  }

  .hero h1 {
    font-size: var(--text-3xl);
  }

  .examples-grid {
    grid-template-columns: 1fr;
  }

  .footer-inner {
    grid-template-columns: 1fr;
  }
}