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

:root {
  --navy: #0f172a;
  --navy-light: #1e293b;
  --navy-mid: #334155;
  --accent: #3b82f6;
  --accent-light: #60a5fa;
  --accent-glow: rgba(59, 130, 246, 0.15);
  --text: #f1f5f9;
  --text-muted: #94a3b8;
  --text-dark: #0f172a;
  --bg-light: #f8fafc;
  --bg-card: #ffffff;
  --border: #e2e8f0;
  --success: #10b981;
  --warning: #f59e0b;
  --radius: 10px;
  --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  line-height: 1.6;
  color: var(--text-dark);
  background: var(--bg-light);
}

img,
svg,
video {
  max-width: 100%;
  height: auto;
}

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* === Header / Nav === */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: var(--navy);
  border-bottom: 1px solid var(--navy-mid);
  backdrop-filter: blur(12px);
}

.nav-container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text);
  text-decoration: none;
  letter-spacing: -0.02em;
}

.nav-links {
  display: flex;
  align-items: center;
  list-style: none;
  gap: 2rem;
}

.nav-links a {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  transition: color 0.2s;
}

.nav-links a:hover {
  color: var(--text);
}

.nav-btn {
  background: var(--accent);
  color: var(--text) !important;
  padding: 0.5rem 1rem;
  border-radius: 6px;
  font-weight: 600 !important;
  transition: background 0.2s !important;
}

.nav-btn:hover {
  background: var(--accent-light) !important;
}

.mobile-menu-btn {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.mobile-menu-btn span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition:
    transform 0.3s,
    opacity 0.3s;
}

/* === Hero === */
.hero {
  background: linear-gradient(135deg, var(--navy) 0%, var(--navy-light) 50%, #1a2744 100%);
  padding: 8rem 1.5rem 5rem;
  text-align: center;
  color: var(--text);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle at 30% 50%, var(--accent-glow) 0%, transparent 50%);
  pointer-events: none;
}

.hero-content {
  position: relative;
  max-width: 700px;
  margin: 0 auto;
}

.hero h1 {
  font-size: 3rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: 1rem;
  line-height: 1.1;
}

.subtitle {
  font-size: 1.25rem;
  color: var(--accent-light);
  margin-bottom: 0.75rem;
  font-weight: 500;
}

.hero-detail {
  color: var(--text-muted);
  font-size: 1.05rem;
  margin-bottom: 2rem;
}

.hero-actions {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

/* === Buttons === */
.btn {
  display: inline-block;
  padding: 0.75rem 1.75rem;
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.95rem;
  text-decoration: none;
  transition:
    transform 0.15s,
    box-shadow 0.2s,
    background 0.2s;
  cursor: pointer;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn-primary {
  background: var(--accent);
  color: white;
  box-shadow: 0 4px 14px rgba(59, 130, 246, 0.3);
}

.btn-primary:hover {
  background: var(--accent-light);
  box-shadow: 0 6px 20px rgba(59, 130, 246, 0.4);
}

.btn-secondary {
  background: transparent;
  color: var(--text);
  border: 2px solid var(--navy-mid);
}

.btn-secondary:hover {
  border-color: var(--accent);
  color: var(--accent-light);
}

.btn-slides {
  display: inline-block;
  margin: 0.75rem 0em;
  padding: 0.6rem 1.25rem !important;
  background: var(--accent);
  color: white;
  border-radius: 6px;
  font-size: 0.85rem;
  font-weight: 600;
  text-decoration: none;
  box-shadow: 0 2px 8px rgba(59, 130, 246, 0.25);
}

.btn-slides:hover {
  background: var(--accent-light);
  box-shadow: 0 4px 12px rgba(59, 130, 246, 0.35);
  transform: none;
}

/* === Sections === */
.section {
  padding: 5rem 0;
}

.section-alt {
  background: white;
}

.section-title {
  font-size: 2rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: 0.5rem;
  letter-spacing: -0.02em;
}

.section-subtitle {
  text-align: center;
  color: var(--text-muted);
  margin-bottom: 2.5rem;
  font-size: 1rem;
}

/* === Instructor === */
.instructor-card {
  display: flex;
  gap: 2.5rem;
  align-items: center;
  background: white;
  border-radius: var(--radius);
  padding: 2.5rem;
  box-shadow: var(--shadow);
  margin-top: 2rem;
}

.instructor-photo {
  width: 180px;
  height: 180px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid var(--accent);
  object-position: 57% 50%;
  flex-shrink: 0;
}

.instructor-info h3 {
  font-size: 1.5rem;
  margin-bottom: 0.25rem;
  color: var(--navy);
}

.instructor-role {
  color: var(--accent) !important;
  font-weight: 600;
  font-size: 1rem;
  margin-bottom: 0.75rem !important;
}

.instructor-info p {
  color: #475569;
  margin-bottom: 1rem;
  line-height: 1.7;
}

.instructor-highlights {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.instructor-highlights li {
  background: var(--accent-glow);
  color: var(--accent);
  padding: 0.35rem 0.9rem;
  border-radius: 20px;
  font-size: 0.85rem;
  font-weight: 600;
}

/* === Overview Grid === */
.overview-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.5rem;
  margin-top: 2rem;
  margin-bottom: 3rem;
}

.overview-card {
  background: var(--bg-light);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.75rem;
  text-align: center;
  transition:
    box-shadow 0.2s,
    transform 0.15s;
}

.overview-card:hover {
  box-shadow: var(--shadow);
  transform: translateY(-2px);
}

.overview-icon {
  font-size: 2rem;
  margin-bottom: 0.75rem;
}

.overview-card h3 {
  font-size: 1.1rem;
  margin-bottom: 0.5rem;
  color: var(--navy);
}

.overview-card p {
  color: var(--text-muted);
  font-size: 0.9rem;
}

/* === Structure Block === */
.structure-block,
.outcomes-block {
  background: var(--bg-light);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 2rem;
  margin-bottom: 2rem;
}

.structure-block h3,
.outcomes-block h3 {
  font-size: 1.25rem;
  margin-bottom: 1.25rem;
  color: var(--navy);
}

.structure-phases {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.phase {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 0.75rem 1rem;
  background: white;
  border-radius: 8px;
  border-left: 4px solid var(--accent);
}

.phase-label {
  font-weight: 700;
  color: var(--accent);
  min-width: 100px;
  font-size: 0.9rem;
}

.phase-desc {
  color: #475569;
}

.outcomes-block ul {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.5rem;
}

.outcomes-block li {
  padding: 0.4rem 0;
  padding-left: 1.5rem;
  position: relative;
  color: #475569;
  font-size: 0.95rem;
}

.outcomes-block li::before {
  content: "\2713";
  position: absolute;
  left: 0;
  color: var(--success);
  font-weight: 700;
}

/* === Weekly Schedule === */
.weeks-container {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.week-card {
  background: white;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  overflow: hidden;
  transition: box-shadow 0.2s;
}

.week-card:hover {
  box-shadow: var(--shadow);
}

.week-header {
  width: 100%;
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1.1rem 1.5rem;
  background: none;
  border: none;
  cursor: pointer;
  text-align: left;
  font-family: inherit;
  transition: background 0.15s;
}

.week-header:hover {
  background: var(--bg-light);
}

.week-number {
  background: var(--accent);
  color: white;
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.3rem 0.7rem;
  border-radius: 6px;
  white-space: nowrap;
  min-width: 65px;
  text-align: center;
}

.week-title {
  flex: 1;
  font-size: 1rem;
  font-weight: 600;
  color: var(--navy);
}

.week-toggle {
  font-size: 1.5rem;
  color: var(--text-muted);
  font-weight: 300;
  line-height: 1;
  transition: transform 0.3s;
  flex-shrink: 0;
}

.week-card.open .week-toggle {
  transform: rotate(45deg);
}

.week-body {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.4s ease;
}

.week-card.open .week-body {
  max-height: 2000px;
}

.week-body > * {
  padding: 0 1.5rem;
}

.week-body > *:last-child {
  padding-bottom: 1.5rem;
}

.week-section {
  margin-bottom: 1rem;
}

.week-section h4 {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-bottom: 0.5rem;
  padding-top: 0.5rem;
}

.week-section ul {
  list-style: disc;
  padding-left: 1.25rem;
  color: #475569;
  font-size: 0.93rem;
}

.week-section li {
  margin-bottom: 0.25rem;
}

/* === Assignment Block === */
.assignment-block {
  background: linear-gradient(135deg, #eff6ff 0%, #f0fdf4 100%);
  border: 1px solid #bfdbfe;
  border-radius: 8px;
  padding: 1.25rem 1.5rem !important;
  margin: 0.5rem 1.5rem 1rem;
}

/* Add margin-top to separate Download Slides button from expanded Week box */
.assignment-block .btn {
  font-size: 1rem;
  color: var(--navy);
  margin-bottom: 0.5rem;
  text-transform: none;
  letter-spacing: normal;
}

.assignment-block p {
  color: #475569;
  font-size: 0.93rem;
  margin-bottom: 0.5rem;
}

.assignment-block ul,
.assignment-block ol {
  list-style: disc;
  padding-left: 1.25rem;
  color: #475569;
  font-size: 0.93rem;
}

.assignment-block ol {
  list-style: decimal;
}

.assignment-block li {
  margin-bottom: 0.2rem;
}

.assignment-block code {
  background: rgba(59, 130, 246, 0.1);
  color: var(--accent);
  padding: 0.15rem 0.4rem;
  border-radius: 4px;
  font-size: 0.85rem;
}

.assignment-block .btn {
  display: inline-block;
  margin-top: 1rem;
  opacity: 1;
  visibility: visible;
  background: var(--accent) !important;
  color: white !important;
  border: none !important;
  padding: 0.75rem 1.5rem !important;
  border-radius: 8px !important;
  font-weight: 600 !important;
}

.assignment-block .btn:hover {
  background: var(--accent-light) !important;
  color: white !important;
}

.assignment-block .btn-primary {
  background-color: var(--accent) !important;
  color: white !important;
  border: none !important;
}

.assignment-time {
  margin-top: 0.75rem;
  font-weight: 600;
  color: var(--accent) !important;
  font-size: 0.85rem !important;
}

/* === Resources === */
.resources-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
  margin-top: 2rem;
}

.resource-card {
  background: var(--bg-light);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.75rem;
}

.resource-card h3 {
  font-size: 1.1rem;
  color: var(--navy);
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--accent);
}

.resource-card ul {
  list-style: none;
}

.resource-card li {
  padding: 0.35rem 0;
  color: #475569;
  font-size: 0.93rem;
  padding-left: 1.25rem;
  position: relative;
}

.resource-card li::before {
  content: "\2022";
  position: absolute;
  left: 0;
  color: var(--accent);
  font-weight: bold;
}

.resource-card code {
  background: rgba(59, 130, 246, 0.08);
  color: var(--accent);
  padding: 0.1rem 0.35rem;
  border-radius: 4px;
  font-size: 0.85rem;
}

.resource-card a {
  color: var(--accent);
  text-decoration: none;
  font-weight: 600;
  transition: color 0.2s;
}

.resource-card a:hover {
  color: var(--accent-light);
  text-decoration: underline;
}

.resource-card em {
  color: var(--text-muted);
}

.curriculum-download {
  text-align: center;
  margin-top: 2.5rem;
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

/* === Assignment Pages === */
.assignment-hero {
  background: linear-gradient(135deg, var(--navy) 0%, var(--navy-light) 100%);
  padding: 7rem 1.5rem 3rem;
  text-align: center;
  color: var(--text);
}

.assignment-hero h1 {
  font-size: 2.5rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: 0.75rem;
}

.assignment-hero .subtitle {
  font-size: 1.15rem;
  color: var(--accent-light);
}

.assignment-content {
  max-width: 850px;
  margin: 0 auto;
  background: white;
  border-radius: var(--radius);
  padding: 3rem 2rem;
}

.assignment-content h2 {
  font-size: 1.5rem;
  color: var(--navy);
  margin-top: 2rem;
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--accent);
}

.assignment-content h2:first-child {
  margin-top: 0;
}

.assignment-content > p {
  color: #475569;
  margin-bottom: 1rem;
  line-height: 1.7;
}

.assignment-content ul,
.assignment-content ol {
  color: #475569;
  margin-bottom: 1rem;
  padding-left: 2rem;
  line-height: 1.7;
}

.assignment-content li {
  margin-bottom: 0.5rem;
}

.assignment-content code {
  background: rgba(59, 130, 246, 0.1);
  color: var(--accent);
  padding: 0.15rem 0.4rem;
  border-radius: 4px;
  font-size: 0.9rem;
}

.assignment-content strong {
  color: var(--navy);
  font-weight: 600;
}

.assignment-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 2rem;
  background: var(--bg-light);
  padding: 1.5rem;
  border-radius: 8px;
  margin: 1.5rem 0 2rem 0;
}

.assignment-meta .meta-item {
  flex: 1;
  min-width: 180px;
}

.assignment-meta .meta-item strong {
  color: var(--navy);
  display: block;
  margin-bottom: 0.25rem;
}

.assignment-meta .meta-item {
  color: #475569;
}

.download-section {
  background: linear-gradient(135deg, #dbeafe 0%, #dcfce7 100%);
  border: 2px solid var(--accent);
  border-radius: var(--radius);
  padding: 2rem;
  margin: 2rem 0;
}

.download-section h3 {
  color: var(--navy);
  font-size: 1.25rem;
  margin-bottom: 0.5rem;
}

.download-section > p {
  color: #475569;
  margin-bottom: 1.5rem;
}

.download-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
}

.download-buttons .btn {
  flex: 0 1 auto;
}

.download-btn {
  border: none !important;
  background: var(--accent) !important;
  color: white !important;
  box-shadow: 0 2px 8px rgba(59, 130, 246, 0.2) !important;
  transition: all 0.2s ease !important;
}

.download-btn:hover {
  background: var(--accent-light) !important;
  box-shadow: 0 4px 12px rgba(59, 130, 246, 0.3) !important;
  transform: translateY(-1px) !important;
}

.assignment-footer {
  margin-top: 3rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border);
  text-align: center;
}

.btn-small {
  padding: 0.5rem 1.25rem;
  font-size: 0.9rem;
}

/* === Setup Page === */
.setup-hero {
  background: linear-gradient(135deg, var(--navy) 0%, var(--navy-light) 100%);
  padding: 7rem 1.5rem 3rem;
  text-align: center;
  color: var(--text);
}

.setup-hero h1 {
  font-size: 2.5rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: 0.75rem;
}

.setup-hero .subtitle {
  font-size: 1.15rem;
  color: var(--accent-light);
  margin-bottom: 0.5rem;
}

.setup-hero-note {
  color: var(--text-muted);
  font-size: 0.95rem;
}

/* Table of Contents */
.setup-toc h2 {
  text-align: center;
  font-size: 1.5rem;
  margin-bottom: 1.5rem;
}

.toc-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
  max-width: 900px;
  margin: 0 auto;
}

.toc-item {
  display: flex;
  align-items: center;
  gap: 1rem;
  background: white;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem 1.25rem;
  text-decoration: none;
  color: inherit;
  transition:
    box-shadow 0.2s,
    transform 0.15s,
    border-color 0.2s;
}

.toc-item:hover {
  box-shadow: var(--shadow);
  transform: translateY(-2px);
  border-color: var(--accent);
}

.toc-number {
  background: var(--accent);
  color: white;
  width: 32px;
  height: 32px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 0.85rem;
  flex-shrink: 0;
}

.toc-item strong {
  display: block;
  font-size: 0.95rem;
  color: var(--navy);
}

.toc-item div span {
  display: block;
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: 0.15rem;
}

/* OS Tabs */
.os-tabs {
  display: flex;
  gap: 0.5rem;
  margin: 1.5rem 0 0;
}

.os-tab {
  padding: 0.5rem 1.25rem;
  border: 2px solid var(--border);
  border-bottom: none;
  border-radius: 8px 8px 0 0;
  background: var(--bg-light);
  cursor: pointer;
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-muted);
  transition: all 0.2s;
}

.os-tab.active {
  background: white;
  color: var(--accent);
  border-color: var(--accent);
  /*
   * Seamless tab trick: pull the active tab down by exactly the border width
   * so it overlaps and hides the top border of .os-content beneath it.
   * position + z-index ensure the tab renders on top of the content panel,
   * making the two elements appear as one connected piece.
   */
  position: relative;
  z-index: 1;
  margin-bottom: -2px;
}

.os-tab:hover:not(.active) {
  color: var(--navy);
  border-color: var(--navy-mid);
}

.os-content {
  display: none;
  background: white;
  border: 2px solid var(--accent);
  border-radius: 0 var(--radius) var(--radius) var(--radius);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
}

.os-content.active {
  display: block;
}

/* Steps */
.step {
  display: flex;
  gap: 1rem;
  margin-bottom: 1.25rem;
}

.step:last-child {
  margin-bottom: 0;
}

.step-number {
  background: var(--navy);
  color: white;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 0.8rem;
  flex-shrink: 0;
  margin-top: 0.1rem;
}

.step-content {
  flex: 1;
}

.step-content h4 {
  font-size: 1rem;
  color: var(--navy);
  margin-bottom: 0.4rem;
}

.step-content p {
  color: #475569;
  font-size: 0.93rem;
  margin-bottom: 0.5rem;
  line-height: 1.6;
}

.step-content ul {
  list-style: disc;
  padding-left: 1.25rem;
  color: #475569;
  font-size: 0.93rem;
  margin-bottom: 0.5rem;
}

.step-content li {
  margin-bottom: 0.25rem;
}

p code,
li code {
  word-break: break-word;
}

/* Code Blocks */
.code-block {
  background: var(--navy);
  border-radius: 6px;
  padding: 0.75rem 1rem;
  margin: 0.5rem 0;
  overflow-x: auto;
}

.code-block code {
  color: #e2e8f0;
  font-size: 0.9rem;
  font-family: "SF Mono", "Fira Code", "Cascadia Code", Consolas, monospace;
  background: none;
  padding: 0;
}

.code-block-multi {
  padding: 1rem 1.25rem;
}

.code-block-multi code {
  white-space: pre;
  display: block;
  line-height: 1.6;
}

/* Callouts */
.callout {
  border-radius: 8px;
  padding: 1rem 1.25rem;
  margin: 1rem 0;
  font-size: 0.93rem;
  line-height: 1.6;
}

.callout strong {
  display: inline;
}

.callout-warning {
  background: #fffbeb;
  border-left: 4px solid var(--warning);
  color: #92400e;
}

.callout-info {
  background: #eff6ff;
  border-left: 4px solid var(--accent);
  color: #1e40af;
}

.callout-success {
  background: #ecfdf5;
  border-left: 4px solid var(--success);
  color: #065f46;
}

.callout-trouble {
  background: #fef2f2;
  border-left: 4px solid #ef4444;
  color: #991b1b;
}

/* Setup Subsections */
.setup-subsection {
  margin-top: 2.5rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border);
}

.setup-subsection:first-of-type {
  border-top: none;
  padding-top: 0;
}

.setup-subsection h3 {
  font-size: 1.2rem;
  color: var(--navy);
  margin-bottom: 0.75rem;
}

.setup-subsection > p {
  color: #475569;
  margin-bottom: 1rem;
  font-size: 0.95rem;
}

/* Library Table */
.library-table {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  margin-top: 1rem;
}

.library-row {
  display: grid;
  grid-template-columns: 140px 1fr 100px 1fr;
  gap: 0.5rem;
  padding: 0.75rem 1rem;
  align-items: center;
  font-size: 0.9rem;
  color: #475569;
  border-bottom: 1px solid var(--border);
}

.library-row:last-child {
  border-bottom: none;
}

.library-row-header {
  background: var(--navy);
  color: var(--text);
  font-weight: 700;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.library-row:not(.library-row-header):nth-child(even) {
  background: var(--bg-light);
}

.library-row code {
  background: rgba(59, 130, 246, 0.08);
  color: var(--accent);
  padding: 0.1rem 0.35rem;
  border-radius: 4px;
  font-size: 0.8rem;
}

/* === Footer === */
.site-footer {
  background: var(--navy);
  color: var(--text-muted);
  text-align: center;
  padding: 2rem 1.5rem;
  font-size: 0.9rem;
}

/* === Responsive === */
@media (max-width: 900px) {
  .overview-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .outcomes-block ul {
    grid-template-columns: 1fr;
  }

  .instructor-card {
    flex-direction: column;
    text-align: center;
  }

  .instructor-highlights {
    justify-content: center;
  }
}

@media (max-width: 768px) {
  .nav-container {
    height: auto;
    padding: 0.75rem 1.5rem;
    gap: 1rem;
  }

  .logo {
    font-size: 1.05rem;
    max-width: 70%;
    line-height: 1.2;
  }

  .mobile-menu-btn {
    display: flex;
  }

  .nav-links {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--navy);
    flex-direction: column;
    padding: 1rem 1.5rem 1.5rem;
    gap: 0.75rem;
    border-bottom: 1px solid var(--navy-mid);
    max-height: calc(100vh - 64px);
    overflow-y: auto;
  }

  .nav-links.open {
    display: flex;
  }

  .hero {
    padding: 6rem 1.5rem 3rem;
  }

  .hero h1 {
    font-size: 2rem;
  }

  .subtitle {
    font-size: 1.05rem;
  }

  .section {
    padding: 3rem 0;
  }

  .section-title {
    font-size: 1.6rem;
  }

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

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

  .week-header {
    padding: 1rem;
    flex-wrap: wrap;
  }

  .week-number {
    order: 1;
  }

  .week-toggle {
    order: 2;
    margin-left: auto;
  }

  .week-title {
    order: 3;
    flex-basis: 100%;
  }

  .week-title {
    font-size: 0.9rem;
  }

  .instructor-photo {
    width: 140px;
    height: 140px;
  }

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

  .setup-hero {
    padding: 6rem 1.5rem 2rem;
  }

  .setup-hero h1 {
    font-size: 1.8rem;
  }

  .assignment-hero {
    padding: 6rem 1.5rem 2rem;
  }

  .assignment-hero h1 {
    font-size: 1.8rem;
  }

  .assignment-content {
    padding: 2rem 1.5rem;
  }

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

  .download-buttons .btn {
    width: 100%;
  }

  .library-row {
    grid-template-columns: 1fr;
    gap: 0.25rem;
    padding: 0.75rem 1rem;
  }

  .library-row-header {
    display: none;
  }

  .library-row span:nth-child(3) {
    font-size: 0.8rem;
    color: var(--accent);
    font-weight: 600;
  }

  .os-tabs {
    gap: 0.25rem;
    flex-wrap: wrap;
  }

  .os-tab {
    padding: 0.4rem 0.75rem;
    font-size: 0.8rem;
  }

  .step {
    flex-direction: column;
    gap: 0.5rem;
  }

  .step-number {
    margin-top: 0;
  }

  .assignment-block {
    margin: 0.5rem 1rem 0;
  }
}

@media (max-width: 520px) {
  .container {
    padding: 0 1rem;
  }

  .hero h1 {
    font-size: 1.75rem;
  }

  .subtitle {
    font-size: 0.98rem;
  }

  .section-title {
    font-size: 1.4rem;
  }

  .setup-hero h1 {
    font-size: 1.6rem;
  }
}