/* ============================================================
   The Master Lab - Universal Design & Accessibility
   Base + Theme styles. Mobile-first. WCAG AA contrast priority.
   ============================================================ */

:root {
  /* Light theme (default) */
  --color-bg: #f8f9fa;
  --color-text: #1a1a1a;
  --color-text-muted: #4a4a4a;
  --color-accent: #005ebb;
  --color-accent-hover: #004a94;
  --color-accent-subtle: #e6f0fa;
  --color-border: #d0d7de;
  --color-surface: #ffffff;
  --color-surface-alt: #eef2f6;
  --color-success: #0a7a3e;
  --color-warning: #9a6700;
  --color-focus: #005ebb;
  --color-skip: #005ebb;
  --font-body: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 2rem;
  --space-xl: 4rem;
  --max-width: 1100px;
  --sidebar-width: 260px;
  --radius: 0.5rem;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 4px 12px rgba(0, 0, 0, 0.1);
  --line-height: 1.65;
  --transition: 0.2s ease;
}

/* Dark theme */
[data-theme="dark"] {
  --color-bg: #121212;
  --color-text: #f0f0f0;
  --color-text-muted: #b0b0b0;
  --color-accent: #4da3ff;
  --color-accent-hover: #7bb8ff;
  --color-accent-subtle: #1a2a3a;
  --color-border: #3a3a3a;
  --color-surface: #1e1e1e;
  --color-surface-alt: #2a2a2a;
  --color-success: #3dd68c;
  --color-warning: #e6b800;
  --color-focus: #4da3ff;
  --color-skip: #4da3ff;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 4px 12px rgba(0, 0, 0, 0.5);
}

/* System preference fallback when no explicit theme set */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --color-bg: #121212;
    --color-text: #f0f0f0;
    --color-text-muted: #b0b0b0;
    --color-accent: #4da3ff;
    --color-accent-hover: #7bb8ff;
    --color-accent-subtle: #1a2a3a;
    --color-border: #3a3a3a;
    --color-surface: #1e1e1e;
    --color-surface-alt: #2a2a2a;
    --color-success: #3dd68c;
    --color-warning: #e6b800;
    --color-focus: #4da3ff;
    --color-skip: #4da3ff;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 4px 12px rgba(0, 0, 0, 0.5);
  }
}

/* Reset & base */
*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  font-size: 100%;
  scroll-behavior: smooth;
}

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

body {
  margin: 0;
  font-family: var(--font-body);
  font-size: 1.0625rem;
  line-height: var(--line-height);
  color: var(--color-text);
  background-color: var(--color-bg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

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

.skip-link:focus {
  top: var(--space-md);
  outline: 3px solid var(--color-text);
  outline-offset: 2px;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  line-height: 1.25;
  margin-top: 0;
  margin-bottom: var(--space-md);
  font-weight: 700;
  color: var(--color-text);
}

h1 {
  font-size: clamp(1.75rem, 4vw, 2.5rem);
}

h2 {
  font-size: clamp(1.4rem, 3vw, 1.85rem);
  margin-top: var(--space-xl);
  border-bottom: 2px solid var(--color-border);
  padding-bottom: var(--space-sm);
}

h3 {
  font-size: clamp(1.15rem, 2.5vw, 1.35rem);
  margin-top: var(--space-lg);
}

p {
  margin-top: 0;
  margin-bottom: var(--space-md);
  max-width: 70ch;
}

a {
  color: var(--color-accent);
  text-decoration: underline;
  text-underline-offset: 0.15em;
  transition: color var(--transition);
}

a:hover,
a:focus {
  color: var(--color-accent-hover);
}

a:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 2px;
}

/* Header */
.site-header {
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  padding: var(--space-md) 0;
}

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

.logo {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  text-decoration: none;
  color: var(--color-text);
  font-weight: 700;
  font-size: 1.25rem;
}

.logo:hover,
.logo:focus {
  color: var(--color-accent);
  text-decoration: none;
}

.logo-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.5rem;
  height: 2.5rem;
  background: var(--color-accent);
  color: #fff;
  border-radius: var(--radius);
  font-weight: 800;
  font-size: 1.1rem;
  flex-shrink: 0;
}

.theme-toggle {
  background: var(--color-surface-alt);
  border: 2px solid var(--color-border);
  color: var(--color-text);
  padding: var(--space-sm) var(--space-md);
  border-radius: var(--radius);
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  transition: background var(--transition), border-color var(--transition);
}

.theme-toggle:hover,
.theme-toggle:focus-visible {
  background: var(--color-accent-subtle);
  border-color: var(--color-accent);
  outline: 3px solid var(--color-focus);
  outline-offset: 2px;
}

/* Navigation */
.site-nav {
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-md);
}

.nav-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0;
}

.nav-list a {
  display: block;
  padding: var(--space-md) var(--space-sm);
  color: var(--color-text);
  text-decoration: none;
  font-weight: 600;
  border-bottom: 3px solid transparent;
  transition: border-color var(--transition), color var(--transition);
}

.nav-list a:hover,
.nav-list a:focus {
  color: var(--color-accent);
  border-bottom-color: var(--color-accent);
}

.nav-list a[aria-current="page"] {
  color: var(--color-accent);
  border-bottom-color: var(--color-accent);
}

.nav-list a:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: -3px;
}

/* Mobile nav toggle */
.nav-toggle {
  display: none;
  background: transparent;
  border: 2px solid var(--color-border);
  color: var(--color-text);
  padding: var(--space-sm) var(--space-md);
  border-radius: var(--radius);
  font-weight: 600;
  cursor: pointer;
}

.nav-toggle:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 2px;
}

@media (max-width: 720px) {
  .nav-toggle {
    display: inline-block;
    margin: var(--space-sm) 0;
  }
  .nav-list {
    display: none;
    flex-direction: column;
    width: 100%;
  }
  .nav-list.is-open {
    display: flex;
  }
  .nav-list a {
    border-bottom: 1px solid var(--color-border);
    padding: var(--space-md);
  }
}

/* Main layouts */
.layout-single {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-lg) var(--space-md);
  flex: 1;
  width: 100%;
}

.layout-two-col-left,
.layout-two-col-right,
.layout-three-col {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-lg) var(--space-md);
  display: grid;
  gap: var(--space-lg);
  flex: 1;
  width: 100%;
}

.layout-two-col-left {
  grid-template-columns: var(--sidebar-width) 1fr;
}

.layout-two-col-right {
  grid-template-columns: 1fr var(--sidebar-width);
}

.layout-three-col {
  grid-template-columns: var(--sidebar-width) 1fr var(--sidebar-width);
}

@media (max-width: 900px) {
  .layout-two-col-left,
  .layout-two-col-right,
  .layout-three-col {
    grid-template-columns: 1fr;
  }
}

.sidebar {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-md);
  height: fit-content;
}

/* Content helpers */
.main ul,
.main ol,
.layout-single ul,
.layout-single ol {
  padding-left: 1.6rem;
  margin-bottom: var(--space-md);
}

.main li,
.layout-single li {
  margin-bottom: var(--space-sm);
}

/* Cards */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: var(--space-md);
  margin: var(--space-lg) 0;
}

.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-md);
  box-shadow: var(--shadow);
  transition: box-shadow var(--transition), border-color var(--transition);
}

.card:hover {
  box-shadow: var(--shadow-lg);
  border-color: var(--color-accent);
}

.card h3 {
  margin-top: 0;
  font-size: 1.15rem;
}

.card a {
  font-weight: 600;
}

/* Principle cards special */
.principle-card {
  border-left: 4px solid var(--color-accent);
}

.principle-number {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2rem;
  height: 2rem;
  background: var(--color-accent);
  color: #fff;
  border-radius: 50%;
  font-weight: 700;
  font-size: 0.95rem;
  margin-right: var(--space-sm);
}

/* Callouts / boxes */
.callout {
  background: var(--color-accent-subtle);
  border-left: 4px solid var(--color-accent);
  padding: var(--space-md);
  border-radius: 0 var(--radius) var(--radius) 0;
  margin: var(--space-lg) 0;
}

.callout strong {
  display: block;
  margin-bottom: var(--space-xs);
}

.takeaway {
  background: var(--color-surface-alt);
  border: 1px solid var(--color-border);
  padding: var(--space-md);
  border-radius: var(--radius);
  margin: var(--space-lg) 0;
}

.takeaway h3 {
  margin-top: 0;
  color: var(--color-accent);
}

/* Example boxes */
.example-box {
  background: var(--color-surface);
  border: 1px dashed var(--color-border);
  padding: var(--space-md);
  border-radius: var(--radius);
  margin: var(--space-md) 0;
}

.example-box h4 {
  margin-top: 0;
  font-size: 1rem;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

/* Self-check / quiz style */
.self-check {
  background: var(--color-surface);
  border: 2px solid var(--color-accent);
  border-radius: var(--radius);
  padding: var(--space-md);
  margin: var(--space-lg) 0;
}

.self-check h3 {
  margin-top: 0;
}

.self-check details {
  margin-top: var(--space-sm);
}

.self-check summary {
  cursor: pointer;
  font-weight: 600;
  color: var(--color-accent);
  padding: var(--space-sm) 0;
}

.self-check summary:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 2px;
}

/* Progress / learning path */
.learning-path {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  margin: var(--space-lg) 0;
  list-style: none;
  padding: 0;
  counter-reset: path;
}

.learning-path li {
  counter-increment: path;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-md);
  flex: 1 1 180px;
  position: relative;
}

.learning-path li::before {
  content: counter(path);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 1.75rem;
  height: 1.75rem;
  background: var(--color-accent);
  color: #fff;
  border-radius: 50%;
  font-weight: 700;
  font-size: 0.85rem;
  margin-right: var(--space-sm);
}

/* Tables */
table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--space-lg) 0;
  font-size: 0.95rem;
}

th, td {
  border: 1px solid var(--color-border);
  padding: var(--space-sm) var(--space-md);
  text-align: left;
  vertical-align: top;
}

th {
  background: var(--color-surface-alt);
  font-weight: 700;
}

caption {
  text-align: left;
  font-weight: 600;
  margin-bottom: var(--space-sm);
  caption-side: top;
}

/* Forms */
.form-group {
  margin-bottom: var(--space-md);
}

label {
  display: block;
  font-weight: 600;
  margin-bottom: var(--space-xs);
}

input[type="text"],
input[type="email"],
textarea,
select {
  width: 100%;
  max-width: 40rem;
  padding: var(--space-sm) var(--space-md);
  font-size: 1rem;
  font-family: inherit;
  border: 2px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-surface);
  color: var(--color-text);
}

input:focus-visible,
textarea:focus-visible,
select:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 2px;
  border-color: var(--color-accent);
}

button,
.button {
  display: inline-block;
  background: var(--color-accent);
  color: #fff;
  border: none;
  padding: var(--space-sm) var(--space-lg);
  font-size: 1rem;
  font-weight: 600;
  border-radius: var(--radius);
  cursor: pointer;
  text-decoration: none;
  transition: background var(--transition);
}

button:hover,
.button:hover {
  background: var(--color-accent-hover);
  color: #fff;
  text-decoration: none;
}

button:focus-visible,
.button:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 3px;
}

.button-secondary {
  background: transparent;
  color: var(--color-accent);
  border: 2px solid var(--color-accent);
}

.button-secondary:hover {
  background: var(--color-accent-subtle);
  color: var(--color-accent-hover);
}

/* Footer */
.site-footer {
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
  padding: var(--space-lg) var(--space-md);
  margin-top: auto;
}

.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-lg);
  justify-content: space-between;
}

.footer-inner p {
  margin: 0;
  color: var(--color-text-muted);
  font-size: 0.95rem;
}

.footer-nav {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-md);
}

.footer-nav a {
  color: var(--color-text-muted);
  font-size: 0.95rem;
}

/* Hero */
.hero {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-xl) var(--space-lg);
  margin-bottom: var(--space-xl);
  text-align: center;
}

.hero h1 {
  margin-bottom: var(--space-md);
}

.hero p {
  margin-left: auto;
  margin-right: auto;
  font-size: 1.15rem;
  max-width: 55ch;
}

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

/* Visual diagrams (CSS based) */
.diagram {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-md);
  margin: var(--space-lg) 0;
  overflow-x: auto;
}

.diagram-title {
  font-weight: 700;
  margin-bottom: var(--space-md);
  text-align: center;
}

.udl-principles {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--space-md);
  text-align: center;
}

.udl-box {
  background: var(--color-accent-subtle);
  border-radius: var(--radius);
  padding: var(--space-md);
  border: 2px solid var(--color-accent);
}

.udl-box strong {
  display: block;
  font-size: 1.1rem;
  margin-bottom: var(--space-xs);
  color: var(--color-accent);
}

/* Simple bar visual for "why it matters" */
.stat-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: var(--space-md);
  margin: var(--space-lg) 0;
}

.stat {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-md);
  text-align: center;
}

.stat-number {
  font-size: 2rem;
  font-weight: 800;
  color: var(--color-accent);
  line-height: 1.1;
}

.stat-label {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  margin-top: var(--space-xs);
}

/* Accordion for principles */
.accordion {
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  margin-bottom: var(--space-sm);
  background: var(--color-surface);
}

.accordion summary {
  padding: var(--space-md);
  font-weight: 700;
  cursor: pointer;
  list-style: none;
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.accordion summary::-webkit-details-marker {
  display: none;
}

.accordion summary::before {
  content: "+";
  font-weight: 700;
  color: var(--color-accent);
  width: 1.5rem;
  text-align: center;
}

.accordion[open] summary::before {
  content: "−";
}

.accordion summary:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 2px;
}

.accordion-body {
  padding: 0 var(--space-md) var(--space-md);
  border-top: 1px solid var(--color-border);
}

/* Utility */
.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;
}

.text-center {
  text-align: center;
}

.mt-0 {
  margin-top: 0;
}

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

/* Print */
@media print {
  .site-nav,
  .theme-toggle,
  .nav-toggle,
  .skip-link {
    display: none !important;
  }
  body {
    background: #fff;
    color: #000;
  }
  a {
    color: #000;
    text-decoration: underline;
  }
}