styles.css

:root {
  color-scheme: light;
  font-family:
    -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, ui-sans-serif,
    system-ui, sans-serif;
  font-size: 17px;
  font-synthesis: none;
  --canvas: #f7f3ea;
  --surface: #fffdf8;
  --surface-soft: #f1ede4;
  --sage: #e8efe5;
  --sage-strong: #d5e3d3;
  --rose: #f3e7e8;
  --blue: #e6eef3;
  --butter: #f5ebcb;
  --ink: #26312b;
  --muted: #5d665f;
  --primary: #365b4b;
  --primary-hover: #29483b;
  --on-primary: #fffdf8;
  --focus: #1e5aa8;
  --border: #cfcbbf;
  --border-strong: #7a7b75;
  --danger: #8c3640;
  --radius-sm: 0.35rem;
  --radius-md: 0.65rem;
  --reading-width: 46rem;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    color-scheme: dark;
    --canvas: #171b20;
    --surface: #20262c;
    --surface-soft: #292f36;
    --sage: #25372f;
    --sage-strong: #345243;
    --rose: #3b292f;
    --blue: #263746;
    --butter: #3a3424;
    --ink: #f3f1ea;
    --muted: #bdc5bf;
    --primary: #b4d9c3;
    --primary-hover: #cde6d6;
    --on-primary: #173528;
    --focus: #9bc5ff;
    --border: #465049;
    --border-strong: #78847c;
    --danger: #ffb1b8;
  }
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --canvas: #171b20;
  --surface: #20262c;
  --surface-soft: #292f36;
  --sage: #25372f;
  --sage-strong: #345243;
  --rose: #3b292f;
  --blue: #263746;
  --butter: #3a3424;
  --ink: #f3f1ea;
  --muted: #bdc5bf;
  --primary: #b4d9c3;
  --primary-hover: #cde6d6;
  --on-primary: #173528;
  --focus: #9bc5ff;
  --border: #465049;
  --border-strong: #78847c;
  --danger: #ffb1b8;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--canvas);
  color: var(--ink);
  -webkit-font-smoothing: antialiased;
  line-height: 1.65;
  text-rendering: auto;
}

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

button,
summary,
a {
  -webkit-tap-highlight-color: transparent;
}

a {
  color: var(--primary);
  text-decoration-thickness: 0.08em;
  text-underline-offset: 0.16em;
}

a:hover {
  text-decoration-thickness: 0.13em;
}

button {
  min-height: 2.6rem;
}

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

::selection {
  background: var(--sage-strong);
  color: var(--ink);
}

.skip-link {
  position: fixed;
  top: -5rem;
  left: 1rem;
  z-index: 20;
  padding: 0.65rem 0.9rem;
  border-radius: var(--radius-sm);
  background: var(--ink);
  color: var(--canvas);
}

.skip-link:focus {
  top: 1rem;
}

.brand {
  color: var(--ink);
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: -0.025em;
  text-decoration: none;
}

.brand:hover {
  color: var(--primary);
}

.brand-button {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  min-height: 2.5rem;
  padding: 0;
  border: 0;
  background: transparent;
  cursor: pointer;
}

.theme-toggle {
  display: inline-flex;
  flex: 0 0 auto;
  align-items: center;
  gap: 0.5rem;
  min-height: 2.6rem;
  padding: 0.35rem 0.55rem 0.35rem 0.7rem;
  border: 1px solid var(--border-strong);
  border-radius: 999px;
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
}

.theme-toggle:hover {
  background: var(--sage);
}

.theme-toggle-label {
  font-size: 0.72rem;
  font-weight: 700;
  line-height: 1;
  white-space: nowrap;
}

.theme-toggle-track {
  position: relative;
  width: 1.9rem;
  height: 1.1rem;
  border: 1px solid var(--border-strong);
  border-radius: 999px;
  background: var(--surface-soft);
}

.theme-toggle-thumb {
  position: absolute;
  top: 0.17rem;
  left: 0.17rem;
  width: 0.65rem;
  height: 0.65rem;
  border-radius: 50%;
  background: var(--muted);
}

.theme-toggle[aria-pressed="true"] {
  background: var(--sage);
}

.theme-toggle[aria-pressed="true"] .theme-toggle-track {
  border-color: var(--primary);
  background: var(--sage-strong);
}

.theme-toggle[aria-pressed="true"] .theme-toggle-thumb {
  background: var(--primary);
  transform: translateX(0.8rem);
}

h1,
h2,
h3 {
  font-family: ui-serif, "Iowan Old Style", "Palatino Linotype", Georgia, serif;
}

.course-layout {
  display: grid;
  grid-template-columns: minmax(15rem, 17.5rem) minmax(0, 1fr);
  min-height: 100vh;
}

.course-sidebar {
  position: sticky;
  top: 0;
  align-self: start;
  height: 100vh;
  overflow: auto;
  padding: 1.4rem 1rem 2rem;
  border-right: 1px solid var(--border);
  background: var(--surface);
}

.course-sidebar-header {
  margin: 0 0.35rem 1.1rem;
  padding-bottom: 1.1rem;
  border-bottom: 1px solid var(--border);
}

.course-sidebar-masthead,
.library-masthead {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.course-title {
  margin: 0.85rem 0 0;
  font-family: ui-serif, "Iowan Old Style", "Palatino Linotype", Georgia, serif;
  font-size: 1rem;
  font-weight: 600;
  line-height: 1.35;
}

.lesson-navigation ol {
  display: grid;
  gap: 0.15rem;
  margin: 0;
  padding: 0;
  list-style: none;
}

.lesson-nav-item > a,
.locked-lesson {
  display: grid;
  grid-template-columns: 1.8rem minmax(0, 1fr);
  gap: 0.55rem;
  align-items: start;
  min-height: 2.75rem;
  padding: 0.55rem 0.5rem;
  border-left: 3px solid transparent;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: var(--muted);
  text-decoration: none;
}

.lesson-nav-item > a:hover {
  background: var(--sage);
  color: var(--ink);
}

.lesson-nav-item > a[aria-current="page"] {
  border-left-color: var(--primary);
  background: var(--sage);
  color: var(--ink);
}

.lesson-done > a {
  color: var(--primary);
}

.lesson-number {
  padding-top: 0.08rem;
  color: var(--muted);
  font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
  font-size: 0.72rem;
  font-variant-numeric: tabular-nums;
}

.lesson-link-copy {
  display: grid;
  gap: 0.1rem;
  min-width: 0;
  font-size: 0.83rem;
  font-weight: 600;
  line-height: 1.35;
}

.lesson-link-copy small {
  color: var(--muted);
  font-size: 0.68rem;
  font-weight: 500;
}

.locked-lesson {
  color: var(--muted);
  cursor: not-allowed;
  opacity: 0.76;
}

.compact-course-contents {
  margin: 0;
}

.compact-course-contents > summary {
  display: none;
}

.compact-course-body {
  margin: 0;
  padding: 0;
}

.guided-tools {
  display: grid;
  gap: 0.6rem;
  margin: 1.35rem 0.35rem 0;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
  font-size: 0.82rem;
}

.guided-tools button,
.checkpoint-panel button {
  width: fit-content;
  padding: 0.45rem 0.7rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
  font-weight: 600;
}

.guided-tools button:hover,
.checkpoint-panel button:hover:not(:disabled) {
  border-color: var(--primary);
  background: var(--sage);
}

.guided-tools button:disabled,
.checkpoint-panel button:disabled {
  cursor: not-allowed;
  opacity: 0.55;
}

.guided-tools > small {
  color: var(--muted);
  line-height: 1.45;
}

.mode-label {
  margin: 0;
}

.mode-confirmation {
  padding: 0.75rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--blue);
}

.mode-confirmation p {
  margin-top: 0;
}

.mode-confirmation button + button {
  margin-left: 0.35rem;
}

.parking-lot summary {
  min-height: 2.6rem;
  padding: 0.45rem 0;
  cursor: pointer;
  font-weight: 700;
}

.parking-lot form {
  display: grid;
  gap: 0.4rem;
}

.parking-lot textarea {
  width: 100%;
  min-height: 5rem;
  padding: 0.5rem;
  resize: vertical;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--canvas);
  color: var(--ink);
}

.parking-lot ul {
  display: grid;
  gap: 0.5rem;
  padding-left: 1.25rem;
}

.course-library {
  width: min(100% - 2.5rem, 72rem);
  margin: 0 auto;
  padding: clamp(1.25rem, 4vw, 2.25rem) 0 5rem;
}

.course-overview {
  width: min(100% - 2.5rem, 72rem);
  margin: 0 auto;
  padding: clamp(1.25rem, 4vw, 2.25rem) 0 5rem;
}

.course-overview-masthead {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding-bottom: 1.1rem;
  border-bottom: 1px solid var(--border);
}

.course-overview-hero {
  display: grid;
  grid-template-columns: minmax(0, 1.35fr) minmax(17rem, 0.65fr);
  gap: clamp(2rem, 5vw, 5rem);
  align-items: end;
  padding: clamp(3rem, 7vw, 6rem) 0 clamp(2.5rem, 5vw, 4rem);
}

.course-overview-hero h1 {
  max-width: 13ch;
  margin: 0;
  font-size: clamp(3rem, 7vw, 5.7rem);
  line-height: 0.98;
  text-wrap: balance;
}

.course-overview-summary {
  max-width: 43rem;
  margin: 1.25rem 0 0;
  color: var(--muted);
  font-size: clamp(1.05rem, 2vw, 1.25rem);
}

.course-overview-facts {
  display: grid;
  gap: 0.9rem;
  margin: 0;
  padding: 1.25rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--surface-soft);
}

.course-overview-facts div {
  display: grid;
  gap: 0.15rem;
}

.course-overview-facts dt {
  color: var(--muted);
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.course-overview-facts dd {
  margin: 0;
  line-height: 1.45;
}

.course-overview-start {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 1.5rem;
  align-items: center;
  margin-bottom: clamp(3rem, 6vw, 5rem);
  padding: clamp(1.25rem, 3vw, 1.75rem);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-md);
  background: var(--sage);
}

.course-overview-start h2,
.course-overview-start p {
  margin: 0;
}

.course-overview-start h2 {
  font-size: clamp(1.6rem, 3vw, 2.2rem);
}

.course-overview-start p:last-child {
  margin-top: 0.45rem;
  color: var(--muted);
}

.course-overview-body {
  max-width: 52rem;
  margin: 0 auto;
}

.library-hero {
  width: 100%;
  margin-bottom: clamp(2.5rem, 4vw, 4rem);
}

.library-masthead {
  padding-bottom: 1.1rem;
  border-bottom: 1px solid var(--border);
}

.library-masthead-actions,
.library-navigation {
  display: flex;
  align-items: center;
}

.library-masthead-actions {
  gap: 1.25rem;
}

.library-navigation {
  gap: 1rem;
}

.library-navigation a {
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 700;
  text-decoration: none;
}

.library-navigation a:hover {
  color: var(--primary);
  text-decoration: underline;
}

.library-hero-content {
  display: grid;
  grid-template-columns: minmax(0, 1.35fr) minmax(19rem, 0.65fr);
  gap: clamp(2rem, 4vw, 4rem);
  align-items: center;
  padding: clamp(2.25rem, 4vw, 3.5rem) 0 clamp(1.75rem, 3vw, 2.5rem);
}

.library-eyebrow {
  margin: 0 0 0.8rem;
}

.library-title {
  margin: 0;
  max-width: none;
  font-size: clamp(2.85rem, 5vw, 4.5rem);
  line-height: 0.98;
  text-wrap: pretty;
}

.library-introduction {
  padding-left: clamp(1rem, 2vw, 1.5rem);
  border-left: 1px solid var(--border-strong);
}

.library-summary {
  max-width: 36ch;
  margin: 0;
  font-size: 1.08rem;
}

.library-principles {
  display: grid;
  gap: 0.45rem;
  margin: 1.25rem 0 0;
  padding: 0;
  color: var(--muted);
  font-size: 0.84rem;
  list-style: none;
}

.library-principles li::before {
  content: "→";
  margin-right: 0.55rem;
  color: var(--primary);
  font-weight: 700;
}

.library-hero > .local-note {
  width: fit-content;
  max-width: 100%;
  margin: 0;
  padding: 0.55rem 0.75rem;
  border-left: 3px solid var(--primary);
  background: var(--surface-soft);
  color: var(--muted);
  font-size: 0.8rem;
}

.course-action {
  display: inline-flex;
  min-height: 2.75rem;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.58rem 0.9rem;
  border: 1px solid var(--primary);
  border-radius: var(--radius-sm);
  background: var(--primary);
  color: var(--on-primary);
  font-weight: 700;
  text-decoration: none;
}

.course-action:hover {
  border-color: var(--primary-hover);
  background: var(--primary-hover);
  text-decoration: none;
}

.library-section + .library-section {
  margin-top: clamp(4rem, 8vw, 7rem);
}

.library-section-heading {
  max-width: 43rem;
  margin-bottom: 1.4rem;
}

.library-section-heading h2 {
  margin: 0;
  font-size: clamp(2rem, 4vw, 2.8rem);
  line-height: 1.08;
}

.library-section-heading > p:last-child {
  margin: 0.5rem 0 0;
  color: var(--muted);
}

.track-kicker {
  margin: 0 0 0.25rem;
  color: var(--primary);
  font-size: 0.78rem;
  font-weight: 700;
}

.track-title {
  margin: 0;
  font-size: 1.35rem;
  line-height: 1.2;
}

.track-summary {
  max-width: 30rem;
  margin: 0.5rem 0 0;
  color: var(--muted);
  font-size: 0.88rem;
}

.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 21rem), 1fr));
  gap: 1rem;
}

.course-card {
  display: flex;
  min-width: 0;
  flex-direction: column;
  padding: clamp(1.25rem, 3vw, 1.75rem);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-md);
  background: var(--surface);
}

.course-available {
  background: var(--sage);
}

.featured-course {
  max-width: 50rem;
  border-top: 4px solid var(--primary);
}

.course-card-heading {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 1rem;
}

.course-status {
  margin: 0;
  color: var(--primary);
  font-size: 0.78rem;
  font-weight: 700;
}

.course-card h3,
.roadmap-card h4 {
  margin: 0.45rem 0 0;
  font-family: ui-serif, "Iowan Old Style", "Palatino Linotype", Georgia, serif;
  line-height: 1.2;
}

.course-card h3 {
  font-size: clamp(1.55rem, 3vw, 2rem);
}

.course-card > p:not(.course-status) {
  color: var(--muted);
}

.course-meta {
  font-size: 0.84rem;
}

.course-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin: auto 0 1rem;
  padding: 0;
  color: var(--muted);
  font-size: 0.76rem;
  list-style: none;
}

.course-tags li {
  padding: 0.08rem 0.45rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: color-mix(in srgb, var(--surface) 62%, transparent);
}

.course-action {
  width: fit-content;
  margin-top: auto;
}

.empty-library-state {
  padding: 1.5rem;
  border: 1px dashed var(--border-strong);
  color: var(--muted);
}

.course-roadmap {
  padding-top: clamp(2.5rem, 5vw, 4rem);
  border-top: 1px solid var(--border);
}

.roadmap-groups {
  display: grid;
  gap: 3rem;
}

.roadmap-group {
  display: grid;
  grid-template-columns: minmax(13rem, 0.55fr) minmax(0, 1.45fr);
  gap: clamp(1.5rem, 4vw, 3.5rem);
  align-items: start;
}

.roadmap-list {
  display: grid;
  gap: 0.65rem;
}

.roadmap-card {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 1rem;
  padding: 1rem 1.1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
}

.roadmap-card h4 {
  font-size: 1.18rem;
}

.roadmap-card p:not(.course-status) {
  margin: 0.45rem 0 0;
  color: var(--muted);
  font-size: 0.86rem;
}

.roadmap-card .course-tags {
  margin: 0.75rem 0 0;
}

.planned-label {
  align-self: start;
  padding: 0.2rem 0;
  color: var(--muted);
  font-size: 0.72rem;
  font-weight: 600;
  white-space: nowrap;
}

.lesson {
  width: min(100%, 57rem);
  margin: 0 auto;
  padding: clamp(2.5rem, 6vw, 4.75rem) clamp(1.5rem, 5vw, 3.5rem) 5rem;
}

.lesson > * {
  width: min(100%, var(--reading-width));
  margin-right: auto;
  margin-left: auto;
}

.lesson:focus {
  outline: none;
}

.lesson-header {
  margin-bottom: 1.65rem;
  padding-bottom: 1.35rem;
  border-bottom: 1px solid var(--border);
}

.eyebrow {
  color: var(--primary);
  font-size: 0.79rem;
  font-weight: 700;
  letter-spacing: 0.015em;
}

.lesson-header .eyebrow {
  margin: 0 0 0.4rem;
}

h1 {
  font-size: clamp(2.35rem, 5vw, 3.35rem);
  line-height: 1.04;
  letter-spacing: -0.025em;
}

.lesson-header h1 {
  margin: 0;
}

.lesson-body {
  font-size: 1rem;
}

.lesson-body h2 {
  margin: 3rem 0 0.8rem;
  font-size: clamp(1.55rem, 3vw, 1.9rem);
  line-height: 1.2;
  letter-spacing: -0.012em;
}

.lesson-body h3 {
  margin-top: 2rem;
  line-height: 1.3;
}

.lesson-body p,
.lesson-body li {
  max-width: 68ch;
}

.lesson-body img {
  max-width: 100%;
  height: auto;
}

pre {
  padding: 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
}

.lesson-body pre,
.lesson-body table {
  max-width: 100%;
  overflow: auto;
}

.navigation-notice {
  margin-bottom: 1.3rem;
  padding: 0.75rem 0.9rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--blue);
  color: var(--ink);
}

.course-session-panel {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 0.8rem 1.2rem;
  align-items: center;
  margin-bottom: 1.5rem;
  padding: 0.9rem 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--blue);
}

.course-session-panel .eyebrow,
.course-session-panel h2,
.course-session-panel p {
  margin-top: 0;
}

.course-session-panel h2 {
  margin-bottom: 0.25rem;
  font-size: 1.1rem;
}

.course-session-panel p {
  margin-bottom: 0;
  color: var(--muted);
  font-size: 0.82rem;
}

.course-session-panel > button,
.course-session-panel details button {
  width: fit-content;
  padding: 0.45rem 0.7rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
  font-weight: 700;
}

.course-session-panel > details {
  grid-column: 1 / -1;
  border-top: 1px solid var(--border);
}

.course-session-panel summary {
  padding-top: 0.7rem;
  cursor: pointer;
  font-size: 0.82rem;
  font-weight: 700;
}

.course-session-panel ul {
  margin-bottom: 0.8rem;
  padding-left: 1.25rem;
  color: var(--muted);
  font-size: 0.8rem;
}

.course-session-panel li + li {
  margin-top: 0.3rem;
}

.checkpoint-restart-confirmation {
  display: flex;
  flex-wrap: wrap;
  justify-content: end;
  gap: 0.3rem;
}

.checkpoint-restart {
  background: transparent;
}

.checkpoint-panel {
  margin-top: 0;
  margin-bottom: 2rem;
  padding: 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--sage);
}

.compact-session {
  margin: 0 0 1rem;
  border-bottom: 1px solid var(--border);
}

.compact-session > summary,
.lesson-reference-notes > summary {
  min-height: 2.75rem;
  padding: 0.65rem 0;
  color: var(--muted);
  cursor: pointer;
  font-weight: 700;
}

.compact-session .course-session-panel {
  margin-top: 0;
}

.tutor-led-lesson-body {
  display: grid;
  gap: 1.25rem;
}

.tutor-handoff {
  padding: clamp(1rem, 3vw, 1.35rem);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-md);
  background: var(--blue);
}

.checkpoint-prerequisites {
  margin-block: var(--space-4);
  padding: clamp(1rem, 2.5vw, 1.5rem);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--surface-raised);
}

.checkpoint-prerequisites > .eyebrow,
.checkpoint-prerequisites > h2 {
  margin-top: 0;
}

.checkpoint-prerequisites .lesson-fragment > h1:first-child {
  display: none;
}

.tutor-handoff .eyebrow,
.tutor-handoff h2,
.tutor-handoff p:last-child {
  margin-top: 0;
}

.tutor-handoff h2 {
  margin-bottom: 0.55rem;
  font-size: clamp(1.3rem, 3vw, 1.7rem);
}

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

.lesson-reference-notes {
  margin-top: 0.5rem;
  padding-top: 0.5rem;
  border-top: 1px solid var(--border);
}

.lesson-reference-notes > p {
  color: var(--muted);
  font-size: 0.9rem;
}

.lesson-reference-notes .lesson-fragment {
  padding-top: 0.5rem;
}

.checkpoint-heading {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 1rem;
}

.checkpoint-heading .eyebrow,
.checkpoint-heading h2 {
  margin: 0;
}

.checkpoint-heading h2 {
  font-size: 1.18rem;
}

.checkpoint-heading > span {
  color: var(--muted);
  font-size: 0.78rem;
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

.checkpoint-list {
  display: grid;
  gap: 0;
  margin: 0.85rem 0 0;
  padding: 0;
  list-style: none;
}

.checkpoint-list li {
  display: grid;
  grid-template-columns: 1.8rem minmax(0, 1fr) auto;
  align-items: center;
  gap: 0.65rem;
  min-height: 3.25rem;
  padding: 0.55rem 0;
  border-top: 1px solid var(--border);
}

.checkpoint-marker {
  display: grid;
  width: 1.65rem;
  height: 1.65rem;
  place-items: center;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  color: var(--muted);
  font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
  font-size: 0.72rem;
  font-weight: 700;
}

.checkpoint-current .checkpoint-marker,
.checkpoint-complete .checkpoint-marker {
  border-color: var(--primary);
  background: var(--primary);
  color: var(--on-primary);
}

.checkpoint-copy {
  display: grid;
  line-height: 1.35;
}

.checkpoint-response {
  margin-top: 0.35rem;
  color: var(--ink);
  font-size: 0.8rem;
}

.checkpoint-response-form {
  display: grid;
  grid-column: 2 / -1;
  gap: 0.45rem;
  width: min(100%, 34rem);
  padding: 0.55rem 0 0.25rem;
}

.checkpoint-response-form label {
  font-size: 0.8rem;
  font-weight: 700;
}

.checkpoint-response-form input,
.checkpoint-response-form textarea {
  width: 100%;
  min-height: 2.6rem;
  padding: 0.55rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--canvas);
  color: var(--ink);
  font: inherit;
}

.checkpoint-response-form textarea {
  min-height: 6rem;
  resize: vertical;
}

.checkpoint-copy strong {
  font-size: 0.9rem;
}

.checkpoint-list small {
  display: block;
  color: var(--muted);
  font-size: 0.73rem;
}

.checkpoint-control {
  margin: 2rem 0;
  padding: clamp(1rem, 3vw, 1.4rem);
  border: 1px solid var(--border-strong);
  border-left: 4px solid var(--primary);
  border-radius: var(--radius-md);
  background: var(--sage);
}

.tutor-led-lesson-body .checkpoint-control {
  margin: 0;
}

.checkpoint-control-experiment {
  background: var(--blue);
}

.checkpoint-control .eyebrow,
.checkpoint-control h2,
.checkpoint-control > p:last-child {
  margin-top: 0;
}

.checkpoint-control h2 {
  margin-bottom: 0.65rem;
  font-size: clamp(1.35rem, 3vw, 1.75rem);
}

.checkpoint-control .checkpoint-response-form {
  grid-column: auto;
  width: 100%;
  padding-top: 0;
}

.checkpoint-control button {
  width: fit-content;
  min-height: 2.65rem;
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
  font-weight: 700;
}

.checkpoint-control button:hover:not(:disabled) {
  border-color: var(--primary);
  background: var(--surface-soft);
}

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

.automatic-checkpoint {
  max-width: 12rem;
  text-align: right;
}

.experiment-journal {
  margin: -0.75rem 0 2rem;
  padding: 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--blue);
}

.experiment-journal > p {
  color: var(--muted);
  font-size: 0.86rem;
}

.experiment-journal button {
  padding: 0.4rem 0.6rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
  font-weight: 600;
}

.experiment-group {
  padding-top: 0.8rem;
  border-top: 1px solid var(--border);
}

.experiment-group h3 {
  margin: 0 0 0.65rem;
  font-size: 1rem;
}

.experiment-runs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-bottom: 0.7rem;
}

.experiment-runs button {
  padding: 0.35rem 0.55rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
}

.experiment-runs .selected-baseline {
  border-color: var(--primary);
  background: var(--primary);
  color: var(--on-primary);
}

.experiment-comparison {
  overflow-x: auto;
}

.experiment-comparison table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.82rem;
}

.experiment-comparison caption {
  margin-bottom: 0.35rem;
  text-align: left;
  font-weight: 700;
}

.experiment-comparison th,
.experiment-comparison td {
  padding: 0.4rem;
  border: 1px solid var(--border);
  text-align: left;
}

blockquote {
  margin: 2rem 0;
  padding: 0.9rem 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--blue);
}

blockquote > :first-child {
  margin-top: 0;
}

blockquote > :last-child {
  margin-bottom: 0;
}

code {
  padding: 0.12rem 0.3rem;
  border-radius: 0.22rem;
  background: var(--surface-soft);
  font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
  font-size: 0.9em;
}

pre code {
  padding: 0;
  background: transparent;
}

.explorable,
.exercise {
  margin: 2rem 0;
  padding: 0.75rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
}

.explorable {
  background: var(--surface);
}

.explorable iframe {
  display: block;
  width: 100%;
  border: 0;
  border-radius: var(--radius-sm);
  background: var(--surface);
}

.explorable-status {
  min-height: 1.35rem;
  margin: 0.5rem 0 0;
  color: var(--muted);
  font-size: 0.76rem;
}

.explorable-error {
  margin: 0.65rem 0 0;
  padding: 0.65rem 0.75rem;
  border: 1px solid var(--danger);
  border-radius: var(--radius-sm);
  background: var(--rose);
  color: var(--danger);
}

.exercise {
  padding: 1rem;
  background: var(--butter);
}

.exercise-heading {
  margin: 0;
  font-size: 1.15rem;
}

.exercise-path {
  color: var(--muted);
}

.lesson-pagination {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 4rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border);
}

.lesson-pagination button {
  padding: 0.65rem 0.9rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
  font-weight: 600;
}

.lesson-pagination button:hover:not(:disabled) {
  border-color: var(--primary);
  background: var(--sage);
}

.lesson-pagination button:disabled {
  cursor: not-allowed;
  opacity: 0.52;
}

.next-actions {
  display: grid;
  justify-items: end;
  gap: 0.4rem;
}

.next-actions small {
  max-width: 18rem;
  color: var(--muted);
  text-align: right;
}

.lesson-pagination .secondary-action {
  border-style: dashed;
  background: transparent;
}

.loading,
.fatal-error {
  max-width: 42rem;
  margin: 10vh auto;
  padding: 2rem;
}

@media (max-width: 70rem) {
  .library-hero-content {
    grid-template-columns: minmax(0, 1fr);
    gap: 1.5rem;
    align-items: start;
  }

  .library-title {
    max-width: 16ch;
  }

  .library-introduction {
    max-width: 46rem;
    padding-top: 1.35rem;
    padding-left: 0;
    border-top: 1px solid var(--border-strong);
    border-left: 0;
  }
}

@media (max-width: 62rem) {
  .course-layout {
    display: block;
  }

  .course-sidebar {
    position: static;
    width: 100%;
    height: auto;
    padding: 1rem clamp(1rem, 4vw, 2rem) 1.1rem;
    border-right: 0;
    border-bottom: 1px solid var(--border);
  }

  .course-sidebar-header {
    display: grid;
    align-items: center;
    justify-content: space-between;
    grid-template-columns: minmax(0, 1fr) minmax(0, auto);
    gap: 1rem;
    margin: 0;
    padding: 0;
    border: 0;
  }

  .course-sidebar-masthead {
    min-width: 0;
  }

  .course-title {
    max-width: 65%;
    margin: 0;
    text-align: right;
  }

  .compact-course-contents {
    margin-top: 0.85rem;
  }

  .compact-course-contents > summary {
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto 0.7rem;
    gap: 0.7rem;
    align-items: center;
    min-height: 3rem;
    padding: 0.65rem 0.8rem;
    border: 1px solid var(--border-strong);
    border-radius: var(--radius-sm);
    background: var(--surface);
    color: var(--ink);
    cursor: pointer;
    font-weight: 700;
    list-style: none;
  }

  .compact-course-contents > summary::-webkit-details-marker {
    display: none;
  }

  .compact-course-contents > summary small {
    color: var(--muted);
    font-size: 0.75rem;
    font-weight: 500;
  }

  .contents-chevron {
    width: 0.55rem;
    height: 0.55rem;
    border-right: 2px solid var(--primary);
    border-bottom: 2px solid var(--primary);
    transform: rotate(45deg) translate(-0.1rem, 0.1rem);
  }

  .compact-course-contents[open] .contents-chevron {
    transform: rotate(-135deg) translate(-0.1rem, 0.1rem);
  }

  .compact-course-body {
    max-height: min(70vh, 42rem);
    overflow: auto;
    margin-top: 0.5rem;
    padding: 0.6rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    background: var(--surface);
  }

  .compact-course-body .guided-tools {
    margin-right: 0;
    margin-left: 0;
  }

  .lesson {
    padding-top: 2.5rem;
  }

  .course-overview-hero {
    grid-template-columns: minmax(0, 1fr);
    gap: 2rem;
    align-items: start;
  }

  .course-overview-facts {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 42rem) {
  :root {
    font-size: 16px;
  }

  .course-session-panel {
    display: block;
  }

  .course-session-panel > button {
    margin-top: 0.7rem;
  }

  .course-library {
    width: min(100% - 2rem, 72rem);
    padding-top: 1.5rem;
  }

  .course-overview {
    width: min(100% - 2rem, 72rem);
    padding-top: 1.5rem;
  }

  .course-overview-hero {
    padding: 2.5rem 0;
  }

  .course-overview-hero h1 {
    font-size: clamp(2.6rem, 13vw, 3.8rem);
  }

  .course-overview-facts,
  .course-overview-start {
    grid-template-columns: minmax(0, 1fr);
  }

  .library-hero {
    margin-bottom: 2.5rem;
  }

  .library-hero-content {
    gap: 1.5rem;
    padding: 2.25rem 0 1.75rem;
  }

  .library-title {
    max-width: 13ch;
    font-size: clamp(2.6rem, 13vw, 3.5rem);
  }

  .library-introduction {
    padding-top: 1.1rem;
  }

  .library-section + .library-section {
    margin-top: 4rem;
  }

  .roadmap-group,
  .roadmap-card {
    grid-template-columns: minmax(0, 1fr);
  }

  .roadmap-group {
    gap: 1rem;
  }

  .planned-label {
    justify-self: start;
  }

  .course-action {
    width: 100%;
  }

  .course-sidebar-header {
    display: block;
  }

  .course-sidebar-masthead {
    width: 100%;
  }

  .course-title {
    max-width: none;
    margin-top: 0.45rem;
    text-align: left;
  }

  .compact-course-contents > summary {
    align-items: flex-start;
  }

  .lesson {
    padding: 2rem 1rem 4rem;
  }

  h1 {
    font-size: clamp(2.15rem, 12vw, 2.75rem);
  }

  .checkpoint-heading {
    display: block;
  }

  .checkpoint-heading > span {
    display: block;
    margin-top: 0.25rem;
  }

  .checkpoint-list li {
    grid-template-columns: 1.8rem minmax(0, 1fr);
  }

  .checkpoint-list button,
  .automatic-checkpoint {
    grid-column: 2;
    max-width: none;
    text-align: left;
  }

  .lesson-pagination {
    align-items: stretch;
    flex-direction: column;
  }

  .lesson-pagination > span:empty {
    display: none;
  }

  .next-actions {
    justify-items: stretch;
  }

  .next-actions small {
    text-align: left;
  }
}

@media (max-width: 32rem) {
  .library-navigation {
    display: none;
  }
}

@media (prefers-reduced-motion: no-preference) {
  a,
  button,
  summary {
    transition:
      color 160ms ease,
      border-color 160ms ease,
      background-color 160ms ease;
  }

  .theme-toggle-thumb {
    transition: transform 160ms ease;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms;
    animation-iteration-count: 1;
    scroll-behavior: auto;
    transition-duration: 0.01ms;
  }
}