:root {
  color-scheme: dark;
  --bg: #050606;
  --surface: #0d0f0f;
  --surface-2: #141716;
  --text: #f3f5f2;
  --muted: #a2a8a4;
  --faint: #69706c;
  --line: #292d2b;
  --line-strong: #414744;
  --accent: #9fffe0;
  --blue: #83c9ff;
  --amber: #ffc77d;
  --green: #9fe4b5;
  --danger: #ffb39d;
  --max: 1160px;
  --radius: 6px;
  --shadow: 0 24px 70px rgba(0, 0, 0, 0.35);
}

.source-lesson-main {
  max-width: 920px;
  padding-top: 48px;
  padding-bottom: 96px;
}

.source-lesson-header {
  margin: 28px 0 44px;
  padding-bottom: 32px;
  border-bottom: 1px solid var(--line);
}

.source-lesson-display-title {
  max-width: 820px;
  margin: 10px 0 14px;
  color: var(--text);
  font-size: clamp(2rem, 5vw, 4.5rem);
  font-weight: 750;
  line-height: 1.02;
}

.source-route-links {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 12px;
  margin-top: 22px;
}

.source-markdown {
  color: var(--muted);
  font-size: 1.02rem;
  line-height: 1.75;
}

.source-markdown h1,
.source-markdown h2,
.source-markdown h3,
.source-markdown h4,
.source-markdown h5,
.source-markdown h6 {
  max-width: 780px;
  margin: 2em 0 0.65em;
  color: var(--text);
  line-height: 1.15;
}

.source-markdown h1 { font-size: 2.4rem; }
.source-markdown h2 { font-size: 1.75rem; }
.source-markdown h3 { font-size: 1.3rem; }

.source-markdown p,
.source-markdown ul,
.source-markdown ol,
.source-markdown blockquote,
.source-markdown pre {
  max-width: 780px;
}

.source-markdown li + li { margin-top: 0.42em; }

.source-markdown blockquote {
  margin-left: 0;
  padding: 2px 0 2px 20px;
  border-left: 2px solid var(--accent);
  color: var(--text);
}

.source-markdown pre {
  overflow-x: auto;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: #080b0a;
  color: var(--text);
  white-space: pre-wrap;
  overflow-wrap: anywhere;
}

.source-markdown code {
  font-family: Consolas, "SFMono-Regular", monospace;
  font-size: 0.92em;
}

.source-markdown img {
  display: block;
  max-width: 100%;
  height: auto;
  margin: 28px 0;
}

.catalog-lesson-row.is-unavailable,
.route-lesson-link.is-unavailable {
  cursor: default;
  opacity: 0.55;
}

@media (max-width: 720px) {
  .source-lesson-main {
    padding-top: 30px;
    padding-bottom: 64px;
  }

  .source-lesson-display-title {
    font-size: 2.2rem;
  }

  .source-markdown h1 { font-size: 1.9rem; }
  .source-markdown h2 { font-size: 1.45rem; }
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  min-width: 320px;
  margin: 0;
  background:
    radial-gradient(circle at 78% 8%, rgba(131, 201, 255, 0.05), transparent 28%),
    var(--bg);
  color: var(--text);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 16px;
  line-height: 1.55;
}

body::before {
  position: fixed;
  inset: 0;
  z-index: -1;
  background-image: radial-gradient(circle, rgba(159, 255, 224, 0.16) 0 1px, transparent 1.4px);
  background-position: 24px 22px;
  background-size: 174px 142px;
  content: "";
  mask-image: linear-gradient(90deg, transparent, black 36%, black 78%, transparent);
  opacity: 0.28;
  pointer-events: none;
}

a {
  color: inherit;
  text-decoration: none;
}

button,
input,
select {
  font: inherit;
}

button,
select {
  cursor: pointer;
}

button:disabled {
  cursor: not-allowed;
}

.shell {
  width: calc(100% - 40px);
  max-width: var(--max);
  margin: 0 auto;
}

.skip-link {
  position: fixed;
  top: 10px;
  left: 10px;
  z-index: 100;
  transform: translateY(-160%);
  border: 1px solid var(--accent);
  border-radius: 4px;
  padding: 8px 12px;
  background: var(--surface);
  color: var(--text);
}

.skip-link:focus-visible {
  transform: translateY(0);
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 30;
  border-bottom: 1px solid rgba(255, 255, 255, 0.07);
  background: rgba(5, 6, 6, 0.9);
  backdrop-filter: blur(16px);
}

.header-inner {
  display: flex;
  min-height: 68px;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.brand {
  display: grid;
  gap: 1px;
  color: var(--text);
}

.brand span {
  font-size: 13px;
  font-weight: 850;
}

.brand small {
  color: var(--faint);
  font-size: 10px;
  font-weight: 700;
  text-transform: uppercase;
}

.main-nav {
  display: flex;
  align-items: center;
  gap: 6px;
}

.main-nav a {
  min-height: 36px;
  border: 1px solid transparent;
  border-radius: 999px;
  padding: 7px 11px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 650;
}

.main-nav a:hover,
.main-nav a:focus-visible,
.main-nav a[aria-current="page"] {
  border-color: var(--line);
  color: var(--text);
}

.course-hero {
  display: grid;
  min-height: min(760px, calc(100vh - 68px));
  grid-template-columns: minmax(0, 1.08fr) minmax(360px, 0.92fr);
  align-items: center;
  gap: 64px;
  padding-top: 56px;
  padding-bottom: 64px;
}

.eyebrow,
.panel-kicker {
  margin: 0 0 12px;
  color: var(--faint);
  font-size: 12px;
  font-weight: 800;
  text-transform: uppercase;
}

.course-hero h1,
.page-intro h1,
.lesson-header h1 {
  margin: 0;
  color: var(--text);
  font-size: 64px;
  line-height: 1;
  letter-spacing: 0;
}

.hero-lead {
  max-width: 680px;
  margin: 24px 0 0;
  color: var(--muted);
  font-size: 20px;
  line-height: 1.45;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 28px;
}

.button {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  padding: 0 17px;
  background: rgba(255, 255, 255, 0.025);
  color: var(--text);
  font-size: 14px;
  font-weight: 750;
  transition: border-color 160ms ease, background-color 160ms ease, color 160ms ease;
}

.button:hover,
.button:focus-visible {
  border-color: var(--accent);
}

.button.primary {
  border-color: var(--text);
  background: var(--text);
  color: #050606;
}

.button.primary:hover,
.button.primary:focus-visible {
  border-color: var(--accent);
  background: var(--accent);
}

.button.compact {
  min-height: 42px;
  align-self: end;
}

.status-line {
  display: flex;
  align-items: center;
  gap: 9px;
  margin-top: 20px;
  color: var(--muted);
  font-size: 13px;
}

.status-dot {
  width: 7px;
  height: 7px;
  border-radius: 999px;
  background: var(--amber);
  box-shadow: 0 0 16px rgba(255, 199, 125, 0.34);
}

.hero-route {
  min-width: 0;
  border-left: 1px solid var(--line);
  padding-left: 34px;
}

.hero-route-list {
  display: grid;
  gap: 0;
}

.hero-route-step {
  position: relative;
  display: grid;
  min-height: 38px;
  grid-template-columns: 32px minmax(0, 1fr);
  align-items: center;
  gap: 10px;
  color: var(--muted);
  font-size: 14px;
  font-weight: 700;
}

.hero-route-step:not(:last-child)::after {
  position: absolute;
  top: 29px;
  bottom: -9px;
  left: 15px;
  width: 1px;
  background: var(--line-strong);
  content: "";
}

.hero-route-step span:first-child {
  display: grid;
  width: 30px;
  height: 30px;
  place-items: center;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  background: var(--surface);
  color: var(--accent);
  font-size: 11px;
}

.output-strip {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 6px;
  margin-top: 28px;
}

.output-strip img {
  display: block;
  width: 100%;
  aspect-ratio: 9 / 16;
  border-radius: 3px;
  object-fit: cover;
  filter: saturate(0.72) brightness(0.72);
}

.progress-band {
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  background: rgba(13, 15, 15, 0.72);
}

.progress-inner {
  display: flex;
  min-height: 134px;
  align-items: center;
  justify-content: space-between;
  gap: 48px;
  padding-top: 24px;
  padding-bottom: 24px;
}

.progress-inner strong {
  display: block;
  font-size: 22px;
}

.progress-inner p:not(.eyebrow) {
  margin: 4px 0 0;
  color: var(--muted);
  font-size: 13px;
}

.progress-actions {
  width: min(360px, 42vw);
}

.progress-track {
  height: 7px;
  overflow: hidden;
  border-radius: 999px;
  background: #242826;
}

.progress-track span {
  display: block;
  width: 0;
  height: 100%;
  border-radius: inherit;
  background: var(--accent);
  transition: width 220ms ease;
}

.text-button {
  border: 0;
  padding: 0;
  background: transparent;
  color: var(--muted);
  font-size: 13px;
  text-decoration: underline;
  text-underline-offset: 4px;
}

.text-button:hover,
.text-button:focus-visible {
  color: var(--text);
}

.text-button:disabled {
  color: var(--faint);
  opacity: 0.55;
}

.progress-actions .text-button {
  margin-top: 12px;
}

.content-section,
.page-main,
.lesson-main {
  padding-top: 64px;
  padding-bottom: 88px;
}

.section-heading {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 44px;
  margin-bottom: 26px;
}

.section-heading h2,
.route-detail h2,
.lesson-step h2,
.empty-state h2 {
  margin: 0;
  font-size: 34px;
  line-height: 1.1;
  letter-spacing: 0;
}

.section-heading > p {
  max-width: 440px;
  margin: 0;
  color: var(--muted);
}

.block-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
}

.block-card {
  display: flex;
  min-width: 0;
  min-height: 290px;
  flex-direction: column;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 22px;
  background: rgba(13, 15, 15, 0.88);
  transition: border-color 180ms ease, transform 180ms ease;
}

.block-card:hover,
.block-card:focus-within {
  border-color: rgba(159, 255, 224, 0.42);
  transform: translateY(-2px);
}

.block-index,
.lesson-order {
  color: var(--accent);
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
  font-size: 12px;
  font-weight: 800;
}

.block-card h3 {
  margin: 12px 0 0;
  font-size: 24px;
  line-height: 1.14;
}

.block-card > p {
  margin: 12px 0 0;
  color: var(--muted);
}

.block-output {
  margin-top: auto;
  padding-top: 20px;
  color: var(--text);
  font-size: 13px;
}

.block-output span {
  display: block;
  margin-bottom: 4px;
  color: var(--faint);
  font-size: 10px;
  font-weight: 800;
  text-transform: uppercase;
}

.block-links {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 18px;
}

.block-links a,
.inline-link {
  color: var(--accent);
  font-size: 13px;
  font-weight: 760;
}

.block-links a:hover,
.block-links a:focus-visible,
.inline-link:hover,
.inline-link:focus-visible {
  color: var(--text);
}

.page-intro {
  max-width: 860px;
  margin-bottom: 34px;
}

.page-intro h1 {
  font-size: 54px;
}

.page-intro > p:last-child {
  max-width: 720px;
  margin: 18px 0 0;
  color: var(--muted);
  font-size: 18px;
}

.filter-panel {
  display: grid;
  grid-template-columns: minmax(280px, 1.45fr) minmax(190px, 0.8fr) minmax(180px, 0.7fr) auto;
  gap: 12px;
  align-items: end;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  padding: 18px 0;
}

.filter-panel label,
.search-field {
  display: grid;
  gap: 7px;
  color: var(--text);
  font-size: 12px;
  font-weight: 760;
}

.filter-panel input,
.filter-panel select,
.search-field input {
  width: 100%;
  min-height: 44px;
  border: 1px solid var(--line-strong);
  border-radius: 4px;
  padding: 0 12px;
  background: #090a0a;
  color: var(--text);
  font-size: 14px;
}

.filter-panel input:hover,
.filter-panel select:hover,
.search-field input:hover {
  border-color: #59605c;
}

.filter-panel input:focus-visible,
.filter-panel select:focus-visible,
.search-field input:focus-visible {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(159, 255, 224, 0.1);
  outline: none;
}

.catalog-summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding: 24px 0 14px;
  color: var(--muted);
  font-size: 13px;
}

.catalog-summary strong {
  color: var(--text);
  font-size: 16px;
}

.lesson-grid {
  display: grid;
  gap: 32px;
}

.catalog-block-group {
  border-top: 1px solid var(--line-strong);
  padding-top: 22px;
}

.catalog-block-header {
  display: grid;
  grid-template-columns: 58px minmax(0, 1fr) auto;
  align-items: center;
  gap: 18px;
  margin-bottom: 12px;
}

.catalog-block-number,
.route-detail-number {
  display: grid;
  width: 58px;
  height: 58px;
  place-items: center;
  border: 1px solid rgba(159, 255, 224, 0.5);
  border-radius: 50%;
  color: var(--accent);
  font-size: 18px;
  font-weight: 850;
}

.catalog-block-header p {
  margin: 0 0 2px;
  color: var(--faint);
  font-size: 11px;
  font-weight: 800;
  text-transform: uppercase;
}

.catalog-block-header h2 {
  margin: 0;
  font-size: 25px;
  line-height: 1.15;
}

.catalog-block-count {
  color: var(--muted);
  font-size: 12px;
}

.catalog-lesson-list {
  display: grid;
  margin-left: 76px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}

.catalog-lesson-row {
  display: grid;
  min-height: 104px;
  grid-template-columns: 50px minmax(0, 1fr) auto;
  align-items: center;
  gap: 18px;
  padding: 16px 18px;
  background: rgba(13, 15, 15, 0.82);
  transition: background-color 160ms ease, box-shadow 160ms ease;
}

.catalog-lesson-row + .catalog-lesson-row {
  border-top: 1px solid var(--line);
}

.catalog-lesson-row:hover,
.catalog-lesson-row:focus-visible {
  background: var(--surface-2);
  box-shadow: inset 3px 0 0 var(--accent);
  outline: none;
}

.catalog-lesson-row.is-complete {
  box-shadow: inset 3px 0 0 var(--green);
}

.catalog-lesson-number,
.route-lesson-number {
  color: var(--accent);
  font-size: 22px;
  font-weight: 850;
  font-variant-numeric: tabular-nums;
}

.catalog-lesson-copy {
  display: grid;
  min-width: 0;
}

.catalog-lesson-copy > span {
  color: var(--faint);
  font-size: 10px;
  font-weight: 800;
  text-transform: uppercase;
}

.catalog-lesson-copy strong {
  margin-top: 3px;
  font-size: 18px;
  line-height: 1.2;
}

.catalog-lesson-copy small {
  max-width: 680px;
  margin-top: 6px;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.4;
}

.catalog-lesson-action {
  display: flex;
  align-items: center;
  gap: 12px;
  color: var(--accent);
  font-size: 13px;
  font-weight: 800;
}

.catalog-lesson-action b {
  font-size: 20px;
  font-weight: 400;
}

.lesson-card {
  position: relative;
  display: grid;
  min-height: 220px;
  grid-template-rows: auto 1fr auto;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 20px;
  background: rgba(13, 15, 15, 0.84);
  transition: border-color 160ms ease, background-color 160ms ease;
}

.lesson-card:hover,
.lesson-card:focus-within {
  border-color: rgba(159, 255, 224, 0.48);
  background: var(--surface);
}

.lesson-card.is-complete {
  border-color: rgba(159, 228, 181, 0.34);
}

.card-meta,
.lesson-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 7px;
  align-items: center;
}

.status-chip,
.type-chip,
.complete-chip {
  display: inline-flex;
  min-height: 24px;
  align-items: center;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 4px 8px;
  color: var(--muted);
  font-size: 10px;
  font-weight: 800;
}

.status-chip[data-status="draft"] {
  border-color: rgba(131, 201, 255, 0.32);
  color: var(--blue);
}

.status-chip[data-status="preview_pending"] {
  border-color: rgba(255, 199, 125, 0.32);
  color: var(--amber);
}

.status-chip[data-status="not_public"] {
  color: var(--faint);
}

.complete-chip {
  border-color: rgba(159, 228, 181, 0.34);
  color: var(--green);
}

.lesson-card h2 {
  margin: 14px 0 0;
  font-size: 21px;
  line-height: 1.2;
}

.lesson-card p {
  margin: 10px 0 0;
  color: var(--muted);
  font-size: 14px;
}

.lesson-card-footer {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 18px;
  margin-top: 18px;
  padding-top: 14px;
  border-top: 1px solid var(--line);
}

.lesson-card-footer span {
  color: var(--faint);
  font-size: 12px;
}

.lesson-card-footer a {
  color: var(--accent);
  font-size: 13px;
  font-weight: 760;
}

.empty-state {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 36px;
  background: var(--surface);
}

.empty-state p {
  max-width: 560px;
  margin: 12px 0 22px;
  color: var(--muted);
}

.sequence-panel {
  overflow-x: auto;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  padding: 20px 0;
}

.sequence-rail {
  display: grid;
  min-width: 840px;
  grid-template-columns: repeat(7, minmax(100px, 1fr));
  align-items: center;
}

.sequence-step {
  position: relative;
  display: grid;
  gap: 8px;
  justify-items: center;
  color: var(--muted);
  font-size: 12px;
  font-weight: 750;
  text-align: center;
}

.sequence-step:not(:last-child)::after {
  position: absolute;
  top: 14px;
  left: calc(50% + 18px);
  width: calc(100% - 36px);
  height: 1px;
  background: var(--line-strong);
  content: "";
}

.sequence-step b {
  position: relative;
  z-index: 1;
  display: grid;
  width: 29px;
  height: 29px;
  place-items: center;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  background: var(--bg);
  color: var(--accent);
  font-size: 11px;
}

.route-layout {
  display: grid;
  grid-template-columns: 290px minmax(0, 1fr);
  gap: 26px;
  margin-top: 34px;
}

.route-blocks {
  display: grid;
  align-content: start;
  gap: 7px;
}

.route-block-button {
  display: grid;
  min-height: 76px;
  grid-template-columns: 42px minmax(0, 1fr);
  align-items: center;
  gap: 10px;
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 8px 10px;
  background: rgba(13, 15, 15, 0.68);
  color: var(--muted);
  text-align: left;
}

.route-block-button span:first-child {
  color: var(--accent);
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
  font-size: 18px;
  font-weight: 850;
}

.route-block-button span:last-child {
  display: grid;
  gap: 3px;
}

.route-block-button small {
  color: var(--faint);
  font-size: 9px;
  font-weight: 800;
  text-transform: uppercase;
}

.route-block-button strong {
  color: inherit;
  font-size: 13px;
  line-height: 1.25;
}

.route-block-button:hover,
.route-block-button:focus-visible,
.route-block-button[aria-pressed="true"] {
  border-color: rgba(159, 255, 224, 0.48);
  background: var(--surface-2);
  color: var(--text);
}

.route-detail {
  min-height: 500px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 28px;
  background: rgba(13, 15, 15, 0.88);
}

.route-detail-header {
  display: grid;
  grid-template-columns: 72px minmax(0, 1fr);
  gap: 20px;
  align-items: start;
}

.route-detail-number {
  width: 72px;
  height: 72px;
  font-size: 24px;
}

.route-detail-header .eyebrow {
  margin-bottom: 6px;
}

.route-detail-header h2 {
  font-size: 36px;
}

.route-detail-header p:last-child {
  max-width: 680px;
  margin: 12px 0 0;
  color: var(--muted);
}

.route-start {
  margin: 24px 0 4px 92px;
}

.route-outcomes {
  display: grid;
  gap: 0;
  margin-top: 28px;
  border-top: 1px solid var(--line);
}

.route-outcomes article {
  display: grid;
  grid-template-columns: 38px minmax(0, 1fr);
  gap: 14px;
  padding: 17px 0;
  border-bottom: 1px solid var(--line);
}

.route-outcomes article > span {
  display: grid;
  width: 30px;
  height: 30px;
  place-items: center;
  border: 1px solid var(--line-strong);
  border-radius: 50%;
  color: var(--accent);
  font-size: 12px;
  font-weight: 850;
}

.route-outcomes strong {
  font-size: 14px;
}

.route-outcomes p {
  margin: 4px 0 0;
  color: var(--muted);
  font-size: 13px;
}

.route-lesson-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  margin-top: 30px;
}

.route-lesson-heading span {
  color: var(--faint);
  font-size: 12px;
}

.route-detail > p {
  max-width: 720px;
  margin: 14px 0 0;
  color: var(--muted);
}

.route-facts {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 10px;
  margin-top: 26px;
}

.route-fact {
  border-top: 1px solid var(--line);
  padding-top: 13px;
}

.route-fact span {
  display: block;
  color: var(--faint);
  font-size: 10px;
  font-weight: 800;
  text-transform: uppercase;
}

.route-fact p {
  margin: 6px 0 0;
  color: var(--text);
  font-size: 13px;
}

.route-lessons {
  display: grid;
  gap: 7px;
  margin-top: 26px;
}

.route-lesson-link {
  display: grid;
  min-height: 58px;
  grid-template-columns: 42px minmax(0, 1fr) auto;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  border-top: 1px solid var(--line);
  padding: 10px 0;
}

.route-lesson-link span {
  color: var(--muted);
  font-size: 12px;
}

.route-lesson-link .route-lesson-number {
  color: var(--accent);
  font-size: 17px;
}

.route-lesson-link strong {
  font-size: 14px;
}

.route-lesson-link:hover strong,
.route-lesson-link:focus-visible strong {
  color: var(--accent);
}

.route-dependencies {
  margin: 22px 0 0;
  color: var(--faint);
  font-size: 12px;
}

.lesson-main {
  max-width: 1080px;
}

.lesson-breadcrumbs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 28px;
  color: var(--muted);
  font-size: 13px;
}

.lesson-breadcrumbs a:hover,
.lesson-breadcrumbs a:focus-visible {
  color: var(--accent);
}

.lesson-header {
  max-width: 860px;
}

.lesson-position {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 14px;
  margin-bottom: 16px;
  color: var(--faint);
  font-size: 12px;
  font-weight: 750;
}

.lesson-position b {
  border-left: 1px solid var(--line-strong);
  padding-left: 14px;
  color: var(--accent);
  font-weight: 850;
}

.lesson-header h1 {
  margin-top: 16px;
  font-size: 52px;
}

.lesson-summary {
  margin: 20px 0 0;
  color: var(--muted);
  font-size: 19px;
}

.lesson-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 280px;
  gap: 38px;
  margin-top: 40px;
}

.lesson-flow {
  display: grid;
  gap: 0;
}

.lesson-step {
  position: relative;
  border-top: 1px solid var(--line);
  padding: 34px 0 40px 68px;
}

.lesson-step::before {
  position: absolute;
  top: 29px;
  left: 0;
  display: grid;
  width: 44px;
  height: 44px;
  place-items: center;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  color: var(--accent);
  content: attr(data-step);
  font-size: 16px;
  font-weight: 850;
}

.lesson-step::after {
  position: absolute;
  top: 74px;
  bottom: -1px;
  left: 21px;
  width: 1px;
  background: var(--line);
  content: "";
}

.lesson-step:last-of-type::after {
  display: none;
}

.lesson-step h2 {
  font-size: 29px;
}

.lesson-step > p {
  margin: 12px 0 0;
  color: var(--muted);
}

.lesson-step ul,
.lesson-step ol {
  display: grid;
  gap: 10px;
  margin: 16px 0 0;
  padding-left: 22px;
  color: var(--text);
}

.lesson-step li::marker {
  color: var(--accent);
}

.result-box {
  border-left: 3px solid var(--accent);
  padding: 4px 0 4px 18px;
}

.result-box strong {
  display: block;
  font-size: 18px;
}

.artifact-state {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-top: 18px;
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 14px;
  background: var(--surface);
}

.artifact-state p {
  margin: 3px 0 0;
  color: var(--muted);
  font-size: 13px;
}

.lesson-aside {
  align-self: start;
  position: sticky;
  top: 92px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px;
  background: var(--surface);
}

.lesson-aside h2 {
  margin: 0;
  font-size: 16px;
}

.lesson-aside dl {
  display: grid;
  gap: 14px;
  margin: 18px 0 0;
}

.lesson-aside dt {
  color: var(--faint);
  font-size: 10px;
  font-weight: 800;
  text-transform: uppercase;
}

.lesson-aside dd {
  margin: 3px 0 0;
  color: var(--muted);
  font-size: 13px;
}

.complete-button {
  width: 100%;
  margin-top: 18px;
}

.complete-button[aria-pressed="true"] {
  border-color: rgba(159, 228, 181, 0.5);
  background: rgba(159, 228, 181, 0.1);
  color: var(--green);
}

.lesson-navigation {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin-top: 28px;
  border-top: 1px solid var(--line);
  padding-top: 24px;
}

.lesson-nav-link {
  min-height: 84px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 14px;
  background: rgba(13, 15, 15, 0.76);
}

.lesson-nav-link.next {
  text-align: right;
}

.lesson-nav-link span {
  display: block;
  color: var(--faint);
  font-size: 10px;
  font-weight: 800;
  text-transform: uppercase;
}

.lesson-nav-link strong {
  display: block;
  margin-top: 5px;
  font-size: 14px;
}

.lesson-nav-link:hover,
.lesson-nav-link:focus-visible {
  border-color: rgba(159, 255, 224, 0.46);
}

.loading-state,
.error-state {
  min-height: 420px;
  display: grid;
  place-items: center;
  color: var(--muted);
}

.error-panel {
  max-width: 620px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 28px;
  background: var(--surface);
}

.error-panel h1 {
  margin: 0;
  font-size: 30px;
}

.error-panel p {
  color: var(--muted);
}

.glossary-search {
  max-width: 560px;
  margin-bottom: 28px;
}

.glossary-list {
  display: grid;
  gap: 0;
}

.glossary-item {
  display: grid;
  grid-template-columns: 210px minmax(0, 1fr) minmax(0, 1.3fr) 150px;
  gap: 20px;
  align-items: start;
  border-top: 1px solid var(--line);
  padding: 22px 0;
}

.glossary-item h2 {
  margin: 0;
  font-size: 20px;
  line-height: 1.2;
}

.glossary-item p {
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}

.glossary-item p strong {
  display: block;
  margin-bottom: 5px;
  color: var(--faint);
  font-size: 10px;
  text-transform: uppercase;
}

.glossary-item a {
  color: var(--accent);
  font-size: 13px;
  font-weight: 760;
}

.site-footer {
  border-top: 1px solid var(--line);
}

.site-footer .shell {
  display: flex;
  min-height: 110px;
  align-items: center;
  justify-content: space-between;
  gap: 30px;
  color: var(--muted);
  font-size: 12px;
}

.site-footer strong {
  color: var(--text);
}

.site-footer p {
  max-width: 680px;
  margin: 0;
  text-align: right;
}

.site-footer a {
  color: var(--accent);
}

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

[hidden] {
  display: none !important;
}

@media (max-width: 900px) {
  .course-hero {
    min-height: 0;
    grid-template-columns: 1fr;
    gap: 40px;
  }

  .hero-route {
    border-top: 1px solid var(--line);
    border-left: 0;
    padding-top: 26px;
    padding-left: 0;
  }

  .block-grid,
  .lesson-grid {
    grid-template-columns: 1fr;
  }

  .filter-panel {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .route-layout {
    grid-template-columns: 1fr;
  }

  .route-blocks {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .catalog-lesson-list {
    margin-left: 0;
  }

  .lesson-layout {
    grid-template-columns: 1fr;
  }

  .lesson-aside {
    position: static;
    order: -1;
  }

  .glossary-item {
    grid-template-columns: 170px minmax(0, 1fr) minmax(0, 1.2fr);
  }

  .glossary-item a {
    grid-column: 2 / -1;
  }
}

@media (max-width: 620px) {
  .shell {
    width: calc(100% - 32px);
  }

  body::before {
    opacity: 0.18;
  }

  .header-inner {
    min-height: 64px;
    align-items: flex-start;
    padding-top: 12px;
    padding-bottom: 10px;
  }

  .brand small {
    display: none;
  }

  .main-nav {
    flex-wrap: wrap;
    justify-content: flex-end;
    gap: 2px;
  }

  .main-nav a {
    min-height: 32px;
    padding: 5px 8px;
    font-size: 11px;
  }

  .main-nav a:last-child {
    display: none;
  }

  .course-hero {
    padding-top: 42px;
    padding-bottom: 46px;
  }

  .course-hero h1,
  .page-intro h1,
  .lesson-header h1 {
    font-size: 42px;
    line-height: 1.04;
  }

  .hero-lead,
  .lesson-summary,
  .page-intro > p:last-child {
    font-size: 17px;
  }

  .hero-actions {
    display: grid;
    grid-template-columns: 1fr;
  }

  .button {
    width: 100%;
  }

  .hero-route-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 8px;
  }

  .hero-route-step {
    min-height: 40px;
    grid-template-columns: 28px minmax(0, 1fr);
    font-size: 12px;
  }

  .hero-route-step:not(:last-child)::after {
    display: none;
  }

  .hero-route-step span:first-child {
    width: 27px;
    height: 27px;
  }

  .output-strip {
    margin-top: 20px;
  }

  .progress-inner,
  .section-heading,
  .site-footer .shell {
    display: grid;
  }

  .progress-inner {
    gap: 18px;
  }

  .progress-actions {
    width: 100%;
  }

  .content-section,
  .page-main,
  .lesson-main {
    padding-top: 42px;
    padding-bottom: 60px;
  }

  .section-heading {
    align-items: start;
    gap: 12px;
  }

  .section-heading h2,
  .route-detail h2,
  .lesson-step h2,
  .empty-state h2 {
    font-size: 28px;
  }

  .block-card {
    min-height: 0;
    padding: 18px;
  }

  .filter-panel {
    grid-template-columns: 1fr;
  }

  .catalog-summary {
    align-items: start;
    flex-direction: column;
    gap: 4px;
  }

  .catalog-block-header {
    grid-template-columns: 46px minmax(0, 1fr);
    gap: 12px;
  }

  .catalog-block-number {
    width: 46px;
    height: 46px;
    font-size: 15px;
  }

  .catalog-block-header h2 {
    font-size: 21px;
  }

  .catalog-block-count {
    display: none;
  }

  .catalog-lesson-row {
    min-height: 0;
    grid-template-columns: 36px minmax(0, 1fr);
    gap: 10px;
    padding: 15px 14px;
  }

  .catalog-lesson-number {
    align-self: start;
    padding-top: 15px;
    font-size: 17px;
  }

  .catalog-lesson-copy strong {
    font-size: 16px;
  }

  .catalog-lesson-action {
    grid-column: 2;
    justify-self: start;
    margin-top: 4px;
  }

  .lesson-card {
    min-height: 0;
    padding: 17px;
  }

  .lesson-card-footer {
    align-items: start;
    flex-direction: column;
    gap: 7px;
  }

  .sequence-panel {
    overflow: visible;
  }

  .sequence-rail {
    min-width: 0;
    grid-template-columns: 1fr;
    gap: 7px;
  }

  .sequence-step {
    min-height: 40px;
    grid-template-columns: 30px minmax(0, 1fr);
    justify-items: start;
    text-align: left;
  }

  .sequence-step:not(:last-child)::after {
    top: 29px;
    bottom: -8px;
    left: 14px;
    width: 1px;
    height: auto;
  }

  .route-blocks {
    grid-template-columns: 1fr;
  }

  .route-detail {
    min-height: 0;
    padding: 20px;
  }

  .route-detail-header {
    grid-template-columns: 48px minmax(0, 1fr);
    gap: 12px;
  }

  .route-detail-number {
    width: 48px;
    height: 48px;
    font-size: 17px;
  }

  .route-detail-header h2 {
    font-size: 27px;
  }

  .route-start {
    width: 100%;
    margin: 20px 0 0;
  }

  .route-lesson-link {
    grid-template-columns: 34px minmax(0, 1fr);
    gap: 9px;
  }

  .route-lesson-link > span:last-child {
    grid-column: 2;
  }

  .route-facts {
    grid-template-columns: 1fr;
  }

  .route-lesson-link {
    align-items: start;
    flex-direction: column;
    gap: 2px;
  }

  .lesson-step {
    padding: 28px 0 34px 50px;
  }

  .lesson-step::before {
    top: 25px;
    width: 34px;
    height: 34px;
    font-size: 13px;
  }

  .lesson-step::after {
    top: 66px;
    left: 16px;
  }

  .artifact-state {
    align-items: start;
    flex-direction: column;
  }

  .lesson-navigation {
    grid-template-columns: 1fr;
  }

  .lesson-nav-link.next {
    text-align: left;
  }

  .glossary-item {
    grid-template-columns: 1fr;
    gap: 10px;
  }

  .glossary-item a {
    grid-column: auto;
  }

  .site-footer .shell {
    align-content: center;
    gap: 8px;
    padding-top: 22px;
    padding-bottom: 22px;
  }

  .site-footer p {
    text-align: left;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition-duration: 0.001ms !important;
  }
}