:root {
  color-scheme: dark;
  --bg: #07090e;
  --bg-alt: #0b0f17;
  --surface: #0e1420;
  --surface-2: #131b2b;
  --surface-3: #1a253a;
  --line: #1e2b40;
  --line-light: #2c3e59;
  --text: #f1f5f9;
  --text-bright: #ffffff;
  --muted: #94a3b8;
  --muted-dim: #64748b;
  --blue: #38bdf8;
  --blue-dim: rgba(56, 189, 248, 0.12);
  --blue-glow: rgba(56, 189, 248, 0.25);
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --orange: #f97316;
  --orange-dim: rgba(249, 115, 22, 0.14);
  --green: #10b981;
  --green-dim: rgba(16, 185, 129, 0.14);
  --red: #ef4444;
  --red-dim: rgba(239, 68, 68, 0.14);
  --font-sans: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "Cascadia Code", Menlo, Monaco, Consolas, monospace;
}

* {
  box-sizing: border-box;
}

[hidden] {
  display: none !important;
}

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

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  color: inherit;
  text-decoration: none;
  transition: color 0.15s ease, border-color 0.15s ease;
}

a:hover {
  color: var(--blue);
}

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

.skip {
  position: absolute;
  left: -999px;
  top: 1rem;
  z-index: 100;
  background: var(--blue);
  color: #000;
  font-weight: 700;
  padding: 0.5rem 1rem;
  border-radius: 4px;
}

.skip:focus {
  left: 1rem;
}

.shell {
  max-width: 1180px;
  margin: 0 auto;
  padding: 0 24px;
}

.shell-narrow {
  max-width: 860px;
  margin: 0 auto;
  padding: 0 24px;
}

/* --------------------------------------------------
   HEADER & NAVIGATION
   -------------------------------------------------- */
.site-header {
  border-bottom: 1px solid var(--line);
  background: rgba(7, 9, 14, 0.94);
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 72px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-size: 1.1rem;
  font-weight: 800;
  letter-spacing: -0.01em;
  color: var(--text-bright);
}

.brand-icon {
  width: 32px;
  height: 32px;
  display: block;
}

.brand-name {
  display: flex;
  flex-direction: column;
  line-height: 1.1;
}

.brand-title {
  font-size: 1.12rem;
  font-weight: 800;
  color: var(--text-bright);
}

.brand-title span {
  color: var(--blue);
}

.brand-tagline {
  font-size: 0.58rem;
  font-weight: 700;
  letter-spacing: 0.22em;
  color: var(--orange);
  text-transform: uppercase;
}

.nav-links {
  display: flex;
  gap: 20px;
  align-items: center;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--muted);
}

.nav-links a {
  padding: 6px 4px;
  position: relative;
}

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

.nav-links a.active::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 4px;
  right: 4px;
  height: 2px;
  background: var(--blue);
  border-radius: 1px;
}

.nav-cta {
  background: var(--blue-dim);
  color: var(--blue) !important;
  border: 1px solid rgba(56, 189, 248, 0.3);
  padding: 6px 14px !important;
  border-radius: 4px;
  font-weight: 600;
}

.nav-cta:hover {
  background: var(--accent) !important;
  color: #fff !important;
  border-color: var(--accent) !important;
}

.menu {
  display: none;
  background: var(--surface);
  border: 1px solid var(--line);
  color: var(--text);
  padding: 0.5rem 0.8rem;
  font-weight: 600;
  font-size: 0.88rem;
  border-radius: 4px;
  cursor: pointer;
}

/* --------------------------------------------------
   HERO & BANNERS
   -------------------------------------------------- */
.hero {
  padding: 80px 0 70px;
  background: radial-gradient(circle at 85% 15%, rgba(37, 99, 235, 0.15), transparent 40%),
              radial-gradient(circle at 15% 75%, rgba(249, 115, 22, 0.08), transparent 35%),
              linear-gradient(180deg, var(--bg) 0%, var(--bg-alt) 100%);
  border-bottom: 1px solid var(--line);
  position: relative;
}

.hero-content {
  max-width: 820px;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  color: var(--blue);
  font-size: 0.76rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  margin-bottom: 14px;
}

.eyebrow-orange {
  color: var(--orange);
}

.hero h1,
.page-head h1 {
  font-size: clamp(2.3rem, 5vw, 4.2rem);
  line-height: 1.05;
  letter-spacing: -0.04em;
  margin: 12px 0 20px;
  color: var(--text-bright);
  font-weight: 800;
}

.hero h1 span,
.page-head h1 span {
  color: var(--blue);
}

.hero p,
.page-head p {
  max-width: 680px;
  color: var(--muted);
  font-size: 1.12rem;
  line-height: 1.6;
  margin: 0 0 24px;
}

.actions {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  margin-top: 32px;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  background: var(--accent);
  color: #fff;
  padding: 12px 22px;
  font-weight: 600;
  font-size: 0.92rem;
  border: 1px solid #3b82f6;
  border-radius: 4px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.button:hover {
  background: var(--accent-hover);
  color: #fff;
  border-color: var(--blue);
}

.button:disabled {
  cursor: not-allowed;
  opacity: 0.55;
}

.button.secondary {
  background: var(--surface);
  color: var(--text);
  border-color: var(--line);
}

.button.secondary:hover {
  background: var(--surface-2);
  border-color: var(--blue);
  color: var(--blue);
}

.button.orange {
  background: var(--orange);
  border-color: #ea580c;
  color: #fff;
}

.button.orange:hover {
  background: #ea580c;
  color: #fff;
}

.button.small {
  padding: 7px 14px;
  font-size: 0.84rem;
}

/* --------------------------------------------------
   SECTIONS, HEADINGS, CARDS
   -------------------------------------------------- */
.section {
  padding: 72px 0;
  border-bottom: 1px solid var(--line);
}

.section-alt {
  background: var(--bg-alt);
}

.section-head {
  margin-bottom: 36px;
}

.section h2 {
  font-size: clamp(1.7rem, 3.2vw, 2.6rem);
  letter-spacing: -0.035em;
  line-height: 1.15;
  margin: 8px 0 12px;
  color: var(--text-bright);
}

.lead {
  color: var(--muted);
  font-size: 1.1rem;
  max-width: 720px;
  margin: 0;
}

.grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}

.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
}

.grid-4 {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
}

.card {
  border: 1px solid var(--line);
  background: linear-gradient(135deg, var(--surface), var(--bg));
  padding: 28px;
  border-radius: 6px;
  transition: transform 0.15s ease, border-color 0.15s ease;
  position: relative;
  overflow: hidden;
}

.card:hover {
  border-color: var(--line-light);
}

.card-interactive:hover {
  border-color: var(--blue);
  transform: translateY(-2px);
}

.card h3,
.card h2 {
  margin: 8px 0 10px;
  font-size: 1.18rem;
  color: var(--text-bright);
  letter-spacing: -0.02em;
}

.card p {
  color: var(--muted);
  font-size: 0.94rem;
  margin: 0 0 12px;
}

.card p:last-child {
  margin-bottom: 0;
}

.card ul {
  padding-left: 20px;
  margin: 12px 0;
  color: var(--muted);
  font-size: 0.92rem;
}

.card li {
  margin-bottom: 6px;
}

.card-action {
  margin-top: 12px;
}

.feature-card-blue {
  border-left: 4px solid var(--blue);
}

.feature-card-orange {
  border-left: 4px solid var(--orange);
}

.feature-card-spaced {
  padding: 36px;
  margin-bottom: 32px;
}

.learning-callout {
  padding: 28px 32px;
  margin-bottom: 40px;
}

.feature-row {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  flex-wrap: wrap;
  gap: 16px;
}

.feature-row-wide {
  gap: 20px;
}

.feature-title.feature-title {
  font-size: 1.6rem;
  margin: 0 0 10px;
}

.project-title.project-title {
  font-size: 1.8rem;
  margin: 4px 0 12px;
}

.project-lead {
  max-width: 760px;
  margin-bottom: 20px;
}

.project-details {
  margin-top: 24px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
}

.project-subheading {
  font-size: 1.1rem;
  color: var(--text-bright);
}

.feature-progress {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 16px;
  margin-top: 20px;
  padding-top: 20px;
  border-top: 1px solid var(--line);
}

.progress-flex {
  flex: 1;
  min-width: 260px;
}

.badge-summary-card {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 24px;
  padding: 32px;
}

/* --------------------------------------------------
   TAGS, PILLS, STATUSES
   -------------------------------------------------- */
.tag {
  display: inline-block;
  color: var(--blue);
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  margin-bottom: 6px;
}

.tag-blue {
  color: var(--blue);
}

.tag-orange {
  color: var(--orange);
}

.tag-green {
  color: var(--green);
}

.pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 10px;
  border-radius: 999px;
  font-size: 0.76rem;
  font-weight: 600;
  background: var(--surface-2);
  color: var(--muted);
  border: 1px solid var(--line);
}

.pill-blue {
  background: var(--blue-dim);
  color: var(--blue);
  border-color: rgba(56, 189, 248, 0.3);
}

.pill-orange {
  background: var(--orange-dim);
  color: var(--orange);
  border-color: rgba(249, 115, 22, 0.3);
}

.pill-green {
  background: var(--green-dim);
  color: var(--green);
  border-color: rgba(16, 185, 129, 0.3);
}

.pill-red {
  background: var(--red-dim);
  color: var(--red);
  border-color: rgba(239, 68, 68, 0.3);
}

/* --------------------------------------------------
   ACADEMY & COURSE COMPONENTS
   -------------------------------------------------- */
.course-hero-meta {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin: 20px 0;
}

.pill-row {
  display: flex;
  gap: 8px;
  margin-bottom: 12px;
  flex-wrap: wrap;
}

.section-head-spaced {
  margin-top: 60px;
}

.progress-banner {
  background: var(--surface);
  border: 1px solid var(--line);
  padding: 20px 24px;
  border-radius: 6px;
  margin-bottom: 32px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  flex-wrap: wrap;
}

.progress-info h4 {
  margin: 0 0 4px;
  font-size: 1rem;
  color: var(--text-bright);
}

.progress-info p {
  margin: 0;
  font-size: 0.88rem;
  color: var(--muted);
}

.progress-bar-wrap {
  width: 100%;
  max-width: 320px;
  background: var(--surface-2);
  height: 10px;
  border-radius: 5px;
  overflow: hidden;
  border: 1px solid var(--line);
}

.progress-bar-fill {
  background: linear-gradient(90deg, var(--accent), var(--blue));
  height: 100%;
  width: 0;
  transition: width 0.3s ease;
}

.progress-bar-fill.progress-0 {
  width: 0;
}

.progress-bar-fill.progress-14 {
  width: 14%;
}

.progress-bar-fill.progress-29 {
  width: 29%;
}

.progress-bar-fill.progress-43 {
  width: 43%;
}

.progress-bar-fill.progress-57 {
  width: 57%;
}

.progress-bar-fill.progress-71 {
  width: 71%;
}

.progress-bar-fill.progress-86 {
  width: 86%;
}

.progress-bar-fill.progress-100 {
  width: 100%;
}

.progress-bar-fill.complete {
  background: linear-gradient(90deg, #059669, #10b981);
}

.module-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.module-item {
  border: 1px solid var(--line);
  background: var(--surface);
  border-radius: 6px;
  padding: 24px;
  display: grid;
  grid-template-columns: 70px 1fr auto;
  gap: 20px;
  align-items: center;
  transition: border-color 0.15s ease, background 0.15s ease;
}

.module-item:hover {
  border-color: var(--line-light);
  background: var(--surface-2);
}

.module-num {
  font-size: 1.8rem;
  font-weight: 800;
  color: var(--line-light);
  font-family: var(--font-mono);
  text-align: center;
}

.module-item.passed .module-num {
  color: var(--green);
}

.module-item.in-progress .module-num {
  color: var(--blue);
}

.module-info h3 {
  margin: 0 0 6px;
  font-size: 1.15rem;
  color: var(--text-bright);
}

.module-info p {
  margin: 0 0 10px;
  color: var(--muted);
  font-size: 0.92rem;
}

.module-tags {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.module-action {
  text-align: right;
}

/* --------------------------------------------------
   LESSON & CONTENT ARTICLE LAYOUT
   -------------------------------------------------- */
.lesson-page {
  padding: 48px 0 80px;
}

.breadcrumbs {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.84rem;
  color: var(--muted);
  margin-bottom: 24px;
}

.breadcrumbs a:hover {
  color: var(--blue);
}

.breadcrumbs span {
  color: var(--muted-dim);
}

.lesson-head {
  border-bottom: 1px solid var(--line);
  padding-bottom: 28px;
  margin-bottom: 36px;
}

.lesson-head h1 {
  font-size: clamp(2rem, 4vw, 3rem);
  letter-spacing: -0.035em;
  margin: 10px 0 16px;
  color: var(--text-bright);
}

.lesson-meta {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.lesson-body {
  font-size: 1.05rem;
  line-height: 1.75;
  color: #cbd5e1;
}

.lesson-body h2 {
  font-size: 1.6rem;
  letter-spacing: -0.025em;
  color: var(--text-bright);
  margin: 44px 0 16px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
}

.lesson-body h3 {
  font-size: 1.25rem;
  letter-spacing: -0.015em;
  color: var(--text-bright);
  margin: 28px 0 12px;
}

.lesson-body p {
  margin: 0 0 20px;
}

.lesson-body ul,
.lesson-body ol {
  margin: 0 0 24px;
  padding-left: 24px;
}

.lesson-body li {
  margin-bottom: 8px;
}

.lesson-body strong {
  color: var(--text-bright);
  font-weight: 600;
}

/* --------------------------------------------------
   CALLOUT BOXES & HIGHLIGHTS
   -------------------------------------------------- */
.callout {
  border-left: 4px solid var(--blue);
  background: var(--surface);
  border-radius: 0 6px 6px 0;
  padding: 18px 22px;
  margin: 28px 0;
  font-size: 0.96rem;
}

.callout-title {
  font-weight: 700;
  font-size: 0.88rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.callout p:last-child {
  margin-bottom: 0;
}

.callout-concept {
  border-left-color: var(--blue);
  background: rgba(14, 20, 32, 0.9);
}

.callout-concept .callout-title {
  color: var(--blue);
}

.callout-defense {
  border-left-color: var(--orange);
  background: rgba(24, 18, 14, 0.6);
  border-top: 1px solid rgba(249, 115, 22, 0.15);
  border-right: 1px solid rgba(249, 115, 22, 0.15);
  border-bottom: 1px solid rgba(249, 115, 22, 0.15);
}

.callout-defense .callout-title {
  color: var(--orange);
}

.callout-incident {
  border-left-color: var(--red);
  background: rgba(28, 14, 16, 0.6);
  border-top: 1px solid rgba(239, 68, 68, 0.15);
  border-right: 1px solid rgba(239, 68, 68, 0.15);
  border-bottom: 1px solid rgba(239, 68, 68, 0.15);
}

.callout-incident .callout-title {
  color: #f87171;
}

.callout-warning {
  border-left-color: #eab308;
  background: rgba(26, 24, 12, 0.6);
}

.callout-warning .callout-title {
  color: #facc15;
}

/* --------------------------------------------------
   TECHNICAL DIAGRAMS, TABLES, HEADERS
   -------------------------------------------------- */
.diagram-box {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 24px;
  margin: 32px 0;
  overflow-x: auto;
}

.diagram-caption {
  font-size: 0.84rem;
  color: var(--muted);
  text-align: center;
  margin-top: 14px;
  font-family: var(--font-mono);
}

.layer-table {
  width: 100%;
  border-collapse: collapse;
  margin: 24px 0;
  font-size: 0.92rem;
}

.layer-table th,
.layer-table td {
  padding: 12px 16px;
  border: 1px solid var(--line);
  text-align: left;
}

.layer-table th {
  background: var(--surface-2);
  color: var(--text-bright);
  font-weight: 600;
  font-size: 0.84rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.layer-table td {
  background: var(--surface);
}

.layer-table tr:hover td {
  background: var(--surface-2);
}

/* Packet header visualizer */
.packet-header {
  display: grid;
  grid-template-columns: repeat(32, 1fr);
  gap: 2px;
  background: var(--line);
  border: 2px solid var(--line-light);
  border-radius: 4px;
  padding: 2px;
  margin: 20px 0;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  min-width: 600px;
}

.packet-bit-markers {
  grid-column: span 32;
  display: flex;
  justify-content: space-between;
  padding: 4px 8px;
  color: var(--muted);
  font-size: 0.7rem;
  background: var(--surface-2);
}

.packet-cell {
  background: var(--surface);
  padding: 10px 4px;
  text-align: center;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  color: var(--text-bright);
}

.packet-cell span {
  font-size: 0.62rem;
  color: var(--muted);
  margin-top: 2px;
}

.packet-cell.highlight-blue {
  background: var(--blue-dim);
  color: var(--blue);
  font-weight: 700;
}

.packet-cell.highlight-orange {
  background: var(--orange-dim);
  color: var(--orange);
  font-weight: 700;
}

.span-3 {
  grid-column: span 3;
}

.span-4 {
  grid-column: span 4;
}

.span-6 {
  grid-column: span 6;
}

.span-8 {
  grid-column: span 8;
}

.span-13 {
  grid-column: span 13;
}

.span-16 {
  grid-column: span 16;
}

.span-32 {
  grid-column: span 32;
}

.packet-strong {
  font-weight: 700;
}

.diagram-meta {
  color: var(--muted);
  font-size: 0.7rem;
}

.ethernet-frame {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 4px;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  text-align: center;
}

.frame-cell {
  background: var(--surface-2);
  padding: 12px 6px;
  border: 1px solid var(--line);
}

.frame-cell-blue {
  background: var(--blue-dim);
  border-color: var(--blue);
  color: var(--blue);
}

.frame-cell-orange {
  background: var(--orange-dim);
  border-color: var(--orange);
  color: var(--orange);
}

.encapsulation-stack {
  display: flex;
  flex-direction: column;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 0.86rem;
}

.encapsulation-step {
  background: var(--surface-2);
  padding: 10px;
  border-left: 4px solid var(--line-light);
}

.encapsulation-application {
  border-left-color: #a855f7;
}

.encapsulation-transport {
  border-left-color: var(--blue);
}

.encapsulation-network {
  border-left-color: var(--orange);
}

.encapsulation-link {
  border-left-color: var(--green);
}

/* Code & Terminal Blocks */
.code-block {
  background: #090d14;
  border: 1px solid var(--line);
  border-radius: 6px;
  margin: 24px 0;
  overflow: hidden;
}

.code-header {
  background: var(--surface);
  border-bottom: 1px solid var(--line);
  padding: 8px 16px;
  font-size: 0.78rem;
  color: var(--muted);
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: var(--font-mono);
}

pre {
  margin: 0;
  padding: 16px 20px;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.88rem;
  line-height: 1.6;
  color: #e2e8f0;
}

code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: var(--surface-2);
  color: var(--blue);
  padding: 2px 6px;
  border-radius: 3px;
  border: 1px solid rgba(56, 189, 248, 0.15);
}

pre code {
  background: none;
  padding: 0;
  border: none;
  color: inherit;
}

/* --------------------------------------------------
   QUIZ & ASSESSMENT ENGINE
   -------------------------------------------------- */
.quiz-section {
  margin-top: 64px;
  padding-top: 48px;
  border-top: 2px solid var(--line);
}

.quiz-container {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 32px;
  position: relative;
}

.quiz-header {
  border-bottom: 1px solid var(--line);
  padding-bottom: 20px;
  margin-bottom: 28px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
}

.quiz-header h3 {
  margin: 0;
  font-size: 1.3rem;
  color: var(--text-bright);
}

.quiz-score-pill {
  font-family: var(--font-mono);
  font-size: 0.88rem;
  padding: 6px 14px;
  border-radius: 20px;
  background: var(--surface-2);
  color: var(--muted);
  border: 1px solid var(--line);
}

.quiz-score-pill.passed {
  color: var(--green);
  border-color: var(--green);
}

.quiz-subtitle {
  font-size: 0.92rem;
  margin-top: 4px;
}

.question-card {
  background: var(--bg);
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 24px;
  margin-bottom: 24px;
}

.question-title {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text-bright);
  margin: 0 0 16px;
  line-height: 1.5;
}

.question-num {
  color: var(--blue);
  font-family: var(--font-mono);
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 6px;
}

.options-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.option-btn {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 12px 16px;
  text-align: left;
  color: var(--text);
  font-size: 0.94rem;
  font-family: inherit;
  cursor: pointer;
  display: flex;
  align-items: flex-start;
  gap: 12px;
  transition: all 0.15s ease;
  width: 100%;
}

.option-btn:hover:not(:disabled) {
  border-color: var(--blue);
  background: var(--surface-2);
  color: var(--text-bright);
}

.option-marker {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 0.84rem;
  color: var(--muted);
  background: var(--surface-2);
  width: 24px;
  height: 24px;
  border-radius: 3px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.option-btn.selected {
  border-color: var(--blue);
  background: var(--blue-dim);
}

.option-btn.selected .option-marker {
  background: var(--blue);
  color: #000;
}

.option-btn.correct {
  border-color: var(--green) !important;
  background: var(--green-dim) !important;
  color: #fff !important;
}

.option-btn.correct .option-marker {
  background: var(--green) !important;
  color: #000 !important;
}

.option-btn.incorrect {
  border-color: var(--red) !important;
  background: var(--red-dim) !important;
  color: #fca5a5 !important;
}

.option-btn.incorrect .option-marker {
  background: var(--red) !important;
  color: #fff !important;
}

.question-explanation {
  margin-top: 14px;
  padding: 12px 16px;
  border-radius: 4px;
  font-size: 0.88rem;
  line-height: 1.5;
  display: none;
}

.question-explanation.show {
  display: block;
}

.question-explanation.passed {
  background: var(--green-dim);
  border: 1px solid rgba(16, 185, 129, 0.3);
  color: #d1fae5;
}

.question-explanation.failed {
  background: var(--red-dim);
  border: 1px solid rgba(239, 68, 68, 0.3);
  color: #fee2e2;
}

.quiz-actions {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 16px;
  margin-top: 24px;
}

.quiz-result-box {
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 24px;
  margin-top: 24px;
  text-align: center;
  display: none;
}

.quiz-result-box.show {
  display: block;
}

.quiz-result-box.passed {
  border-color: var(--green);
  background: linear-gradient(180deg, rgba(16, 185, 129, 0.12), rgba(16, 185, 129, 0.02));
}

.quiz-result-box.failed {
  border-color: var(--orange);
  background: linear-gradient(180deg, rgba(249, 115, 22, 0.12), rgba(249, 115, 22, 0.02));
}

.quiz-result-message {
  margin: 10px auto 20px;
}

.quiz-next-actions {
  justify-content: center;
}

/* --------------------------------------------------
   LESSON STEPPER / BOTTOM NAVIGATION
   -------------------------------------------------- */
.lesson-nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 48px;
  padding-top: 28px;
  border-top: 1px solid var(--line);
  flex-wrap: wrap;
}

.lesson-nav-btn {
  display: inline-flex;
  flex-direction: column;
  padding: 16px 20px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 6px;
  min-width: 200px;
  transition: all 0.15s ease;
}

.lesson-nav-btn:hover {
  border-color: var(--blue);
  background: var(--surface-2);
}

.lesson-nav-btn .nav-sub {
  font-size: 0.76rem;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.lesson-nav-btn .nav-title {
  font-size: 0.98rem;
  font-weight: 600;
  color: var(--text-bright);
  margin-top: 4px;
}

.lesson-nav-btn.next {
  text-align: right;
  margin-left: auto;
}

/* --------------------------------------------------
   ACHIEVEMENT BADGE ENGINE & SHOWCASE
   -------------------------------------------------- */
.badge-showcase {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 36px;
  margin: 36px 0;
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 36px;
  align-items: center;
}

.badge-preview-wrap {
  text-align: center;
  background: var(--bg);
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 24px;
}

.badge-svg-canvas {
  width: 100%;
  max-width: 260px;
  height: auto;
  filter: drop-shadow(0 8px 24px rgba(37, 99, 235, 0.25));
}

.badge-locked {
  padding: 36px;
  border-left: 4px solid var(--orange);
}

.badge-locked h3 {
  margin-top: 8px;
}

.badge-locked-description {
  max-width: 680px;
  margin-bottom: 20px;
}

.badge-locked-progress {
  max-width: 400px;
  margin-bottom: 24px;
}

.progress-row {
  display: flex;
  justify-content: space-between;
  color: var(--muted);
  font-size: 0.84rem;
  margin-bottom: 6px;
}

.progress-wide {
  max-width: 100%;
}

.badge-info-section {
  border-bottom: none;
  padding-top: 48px;
}

.badge-form {
  margin-top: 20px;
}

.badge-label {
  display: block;
  margin-bottom: 6px;
}

.badge-input-row {
  display: flex;
  align-items: center;
  gap: 8px;
}

.badge-actions {
  margin-top: 28px;
}

.badge-input {
  width: 100%;
  max-width: 360px;
  padding: 12px 14px;
  background: var(--bg);
  border: 1px solid var(--line);
  border-radius: 4px;
  color: var(--text-bright);
  font-family: inherit;
  font-size: 0.95rem;
  margin-bottom: 12px;
}

.badge-input:focus {
  border-color: var(--blue);
  outline: none;
}

/* --------------------------------------------------
   SEARCH, FORMS, MISC
   -------------------------------------------------- */
.search {
  width: 100%;
  max-width: 500px;
  padding: 13px 16px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 4px;
  color: var(--text);
  font: inherit;
}

.search:focus {
  border-color: var(--blue);
  outline: none;
}

.list {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.list li {
  background: var(--surface);
  border: 1px solid var(--line);
  padding: 20px;
  border-radius: 6px;
}

.notice {
  margin: 24px 0 0;
  padding: 16px 18px;
  border: 1px solid rgba(249, 115, 22, 0.3);
  border-left: 4px solid var(--orange);
  border-radius: 4px;
  background: var(--orange-dim);
  color: var(--muted);
}

.page-head {
  padding: 64px 0 44px;
  border-bottom: 1px solid var(--line);
  background: var(--bg-alt);
}

.footer {
  padding: 44px 0;
  color: var(--muted);
  font-size: 0.88rem;
  border-top: 1px solid var(--line);
  background: var(--bg);
}

.footer-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 20px;
  flex-wrap: wrap;
}

.footer-links {
  display: flex;
  gap: 18px;
  font-size: 0.86rem;
}

.footer-links a {
  color: var(--muted);
}

.footer-links a:hover {
  color: var(--blue);
}

.footer-tagline {
  margin: 6px 0 0;
  color: var(--muted-dim);
  font-size: 0.84rem;
}

.footer-copyright {
  color: var(--muted-dim);
  font-size: 0.84rem;
}

.search-block {
  margin-bottom: 32px;
}

.search-label {
  display: block;
  margin-bottom: 8px;
}

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

.copy-600 {
  max-width: 600px;
}

.copy-640 {
  max-width: 640px;
  margin-bottom: 16px;
}

.copy-700 {
  max-width: 700px;
  margin-bottom: 20px;
}

.copy-720 {
  max-width: 720px;
  margin-bottom: 20px;
}

.progress-home {
  max-width: 380px;
}

.stack-top-16 {
  margin-top: 16px;
}

.stack-top-20 {
  margin-top: 20px;
}

.space-bottom-8.space-bottom-8 {
  margin-bottom: 8px;
}

.flush-title.flush-title {
  margin: 0 0 10px;
}

/* --------------------------------------------------
   RESPONSIVE MEDIA QUERIES
   -------------------------------------------------- */
@media (max-width: 960px) {
  .grid {
    grid-template-columns: repeat(2, 1fr);
  }
  .grid-4 {
    grid-template-columns: repeat(2, 1fr);
  }
  .badge-showcase {
    grid-template-columns: 1fr;
    text-align: center;
  }
  .badge-form {
    display: flex;
    flex-direction: column;
    align-items: center;
  }
}

@media (max-width: 760px) {
  .menu {
    display: block;
  }
  .nav-links {
    display: none;
    position: absolute;
    top: 72px;
    left: 0;
    right: 0;
    padding: 20px 24px;
    background: var(--bg);
    border-bottom: 1px solid var(--line);
    flex-direction: column;
    align-items: flex-start;
    z-index: 100;
    gap: 16px;
  }
  .nav-links.open {
    display: flex;
  }
  .grid,
  .grid-2,
  .grid-4 {
    grid-template-columns: 1fr;
  }
  .module-item {
    grid-template-columns: 1fr;
    text-align: left;
  }
  .module-num {
    text-align: left;
  }
  .module-action {
    text-align: left;
  }
  .hero {
    padding: 56px 0 48px;
  }
  .page-head {
    padding: 48px 0 36px;
  }
  .section {
    padding: 52px 0;
  }
  .footer-content {
    flex-direction: column;
    align-items: flex-start;
  }
  .packet-header {
    min-width: 500px;
  }
}