:root {
  --navy-950: #041322;
  --navy-900: #06192c;
  --navy-850: #09213a;
  --navy-800: #0d2b48;
  --ink: #082042;
  --muted: #526b87;
  --line: #cbdced;
  --surface: #ffffff;
  --page: #f2f7fc;
  --gold: #e2b92f;
  --gold-deep: #b88600;
  --blue: #1769df;
  --cyan: #18c9ec;
  --green: #168c5b;
  --red: #d34f5f;
  --purple: #7658d9;
  --shadow: 0 18px 44px rgba(12, 43, 73, 0.11);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  min-width: 320px;
  margin: 0;
  color: var(--ink);
  background: var(--page);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 16px;
  line-height: 1.6;
}

button,
input,
select {
  font: inherit;
}

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

a {
  color: inherit;
}

.skip-link {
  position: fixed;
  z-index: 20000;
  top: 8px;
  left: 12px;
  padding: 10px 14px;
  border-radius: 8px;
  color: var(--navy-950);
  background: #fff;
  font-weight: 800;
  transform: translateY(-150%);
}

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

.site-header {
  position: sticky;
  z-index: 1000;
  top: 0;
  display: flex;
  min-height: 86px;
  padding: 0 clamp(22px, 3vw, 52px);
  align-items: center;
  justify-content: space-between;
  border-bottom: 2px solid var(--gold);
  color: #fff;
  background: rgba(6, 25, 44, 0.985);
  box-shadow: 0 8px 26px rgba(0, 10, 25, 0.24);
}

.brand {
  display: inline-flex;
  gap: 15px;
  align-items: center;
  text-decoration: none;
}

.brand img {
  display: block;
  width: 64px;
  height: 64px;
  object-fit: contain;
}

.brand > span {
  color: #c9e1f8;
  font-family: Georgia, "Times New Roman", serif;
  font-size: clamp(1.65rem, 2.2vw, 2.15rem);
  font-weight: 800;
  line-height: 1;
}

.brand strong,
.footer-brand strong {
  color: var(--gold);
}

.desktop-nav {
  display: flex;
  gap: clamp(5px, 0.9vw, 16px);
  align-items: center;
}

.desktop-nav > a,
.nav-dropdown > summary {
  position: relative;
  display: inline-flex;
  min-height: 50px;
  padding: 0 12px;
  align-items: center;
  gap: 8px;
  border-radius: 8px;
  color: #dce9f7;
  font-size: 0.95rem;
  font-weight: 750;
  list-style: none;
  text-decoration: none;
  cursor: pointer;
}

.desktop-nav > a::after,
.nav-dropdown > summary::after {
  position: absolute;
  right: 12px;
  bottom: 3px;
  left: 12px;
  height: 3px;
  border-radius: 3px;
  background: var(--gold);
  content: "";
  opacity: 0;
  transform: scaleX(0.4);
  transition: 160ms ease;
}

.desktop-nav > a:hover,
.desktop-nav > a:focus-visible,
.desktop-nav > a.active,
.nav-dropdown > summary:hover,
.nav-dropdown > summary:focus-visible,
.nav-dropdown[open] > summary {
  color: #fff;
  background: rgba(255, 255, 255, 0.075);
}

.desktop-nav > a:hover::after,
.desktop-nav > a:focus-visible::after,
.desktop-nav > a.active::after,
.nav-dropdown > summary:hover::after,
.nav-dropdown > summary:focus-visible::after,
.nav-dropdown[open] > summary::after {
  opacity: 1;
  transform: scaleX(1);
}

.nav-dropdown {
  position: relative;
}

.nav-dropdown > summary::-webkit-details-marker,
.mobile-nav > summary::-webkit-details-marker {
  display: none;
}

.nav-menu {
  position: absolute;
  z-index: 1010;
  top: calc(100% + 9px);
  left: 50%;
  display: grid;
  width: max-content;
  min-width: 230px;
  padding: 9px;
  border: 1px solid #31597d;
  border-radius: 13px;
  background: var(--navy-850);
  box-shadow: 0 20px 48px rgba(0, 7, 18, 0.55);
  transform: translateX(-50%);
}

.nav-menu a,
.mobile-nav nav a {
  padding: 10px 12px;
  border-radius: 8px;
  color: #dce9f7;
  font-size: 0.88rem;
  font-weight: 700;
  text-decoration: none;
}

.nav-menu a:hover,
.nav-menu a:focus-visible,
.mobile-nav nav a:hover,
.mobile-nav nav a:focus-visible {
  color: #fff;
  background: #123657;
}

.mobile-nav {
  position: relative;
  display: none;
}

.mobile-nav > summary {
  display: grid;
  width: 46px;
  height: 46px;
  padding: 11px;
  align-content: space-between;
  border: 1px solid #31597d;
  border-radius: 10px;
  background: var(--navy-800);
  list-style: none;
  cursor: pointer;
}

.mobile-nav > summary span {
  width: 100%;
  height: 2px;
  border-radius: 2px;
  background: #fff;
}

.mobile-nav nav {
  position: absolute;
  top: calc(100% + 12px);
  right: 0;
  display: grid;
  width: min(310px, calc(100vw - 24px));
  padding: 10px;
  border: 1px solid #31597d;
  border-radius: 14px;
  background: var(--navy-850);
  box-shadow: 0 20px 48px rgba(0, 7, 18, 0.6);
}

main {
  width: min(1480px, calc(100% - 36px));
  min-height: 65vh;
  margin: 0 auto;
  padding: 34px 0 64px;
}

.catalog-heading {
  display: flex;
  gap: 26px;
  align-items: flex-end;
  justify-content: space-between;
  margin-bottom: 24px;
}

.eyebrow,
.section-kicker,
.panel-kicker {
  margin: 0 0 5px;
  color: var(--gold-deep);
  font-size: 0.78rem;
  font-weight: 900;
  letter-spacing: 0.12em;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1,
h2,
h3 {
  line-height: 1.15;
}

h1 {
  margin-bottom: 8px;
  font-size: clamp(2.25rem, 5vw, 4rem);
  letter-spacing: -0.045em;
}

.catalog-heading p:not(.eyebrow) {
  max-width: 760px;
  margin-bottom: 0;
  color: var(--muted);
  font-size: 1.05rem;
}

.compiler-link,
.study-button,
.primary-button,
.secondary-button,
.debug-button {
  display: inline-flex;
  min-height: 48px;
  padding: 0 17px;
  align-items: center;
  justify-content: center;
  gap: 9px;
  border: 1px solid transparent;
  border-radius: 9px;
  font-weight: 800;
  text-decoration: none;
  cursor: pointer;
}

.compiler-link,
.primary-button {
  color: #07172a;
  background: var(--gold);
  box-shadow: 0 10px 24px rgba(226, 185, 47, 0.2);
}

.compiler-link {
  flex: 0 0 auto;
}

.course-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 18px;
  padding-bottom: 3px;
  overflow-x: auto;
  scrollbar-width: thin;
}

.course-tab {
  min-height: 44px;
  padding: 0 16px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--ink);
  background: #fff;
  font-weight: 750;
  white-space: nowrap;
  cursor: pointer;
}

.course-tab:hover,
.course-tab:focus-visible {
  border-color: #85afd8;
}

.course-tab.is-active {
  border-color: var(--ink);
  color: #fff;
  background: var(--ink);
}

.catalog-layout {
  display: grid;
  grid-template-columns: 285px minmax(0, 1fr);
  gap: 22px;
  align-items: start;
}

.filter-panel,
.program-results,
.content-card,
.example-sidebar,
.debug-lab {
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--surface);
  box-shadow: var(--shadow);
}

.filter-panel-inner {
  position: sticky;
  top: 106px;
  padding: 22px;
}

.filter-panel label {
  display: block;
  margin: 17px 0 7px;
  font-size: 0.88rem;
  font-weight: 800;
}

.filter-panel .search-label {
  margin-top: 0;
}

.search-control {
  position: relative;
}

.search-control span {
  position: absolute;
  top: 50%;
  left: 13px;
  color: var(--muted);
  font-size: 1.35rem;
  transform: translateY(-54%);
}

.search-control input,
.filter-panel select {
  width: 100%;
  min-height: 48px;
  border: 1px solid #b9cee3;
  border-radius: 9px;
  color: var(--ink);
  background: #f9fbfe;
  outline: none;
}

.search-control input {
  padding: 0 12px 0 42px;
}

.filter-panel select {
  padding: 0 12px;
}

.search-control input:focus,
.filter-panel select:focus {
  border-color: var(--blue);
  box-shadow: 0 0 0 3px rgba(23, 105, 223, 0.12);
}

.clear-filters {
  width: 100%;
  min-height: 44px;
  margin-top: 18px;
  border: 1px solid #a9c2db;
  border-radius: 9px;
  color: var(--ink);
  background: #fff;
  font-weight: 800;
  cursor: pointer;
}

.clear-filters:hover,
.clear-filters:focus-visible {
  background: #edf5fd;
}

.library-note {
  margin-top: 22px;
  padding: 15px;
  border-left: 4px solid var(--cyan);
  border-radius: 9px;
  color: #dceeff;
  background: var(--navy-850);
}

.library-note strong {
  font-size: 0.9rem;
}

.library-note p {
  margin: 5px 0 0;
  color: #b9d2e8;
  font-size: 0.82rem;
  line-height: 1.55;
}

.mobile-filter-panel {
  display: none;
}

.program-results {
  min-height: 430px;
  padding: clamp(20px, 3vw, 32px);
}

.results-heading {
  display: flex;
  gap: 18px;
  align-items: flex-end;
  justify-content: space-between;
  margin-bottom: 22px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--line);
}

.results-heading h2 {
  margin: 0;
  font-size: clamp(1.7rem, 3vw, 2.25rem);
}

.results-heading > p {
  margin: 0;
  color: var(--muted);
  font-weight: 800;
}

.program-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}

.program-card {
  display: flex;
  min-height: 315px;
  padding: 22px;
  flex-direction: column;
  border: 1px solid #c5d8ea;
  border-radius: 14px;
  background: linear-gradient(180deg, #fff, #f8fbff);
  transition: transform 160ms ease, border-color 160ms ease, box-shadow 160ms ease;
}

.program-card:hover {
  border-color: #86acd2;
  box-shadow: 0 14px 30px rgba(10, 53, 91, 0.1);
  transform: translateY(-2px);
}

.card-topline {
  display: flex;
  gap: 10px;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 15px;
}

.course-badge,
.difficulty,
.concept-list li,
.meta-chip {
  display: inline-flex;
  min-height: 28px;
  padding: 3px 9px;
  align-items: center;
  border-radius: 999px;
  font-size: 0.74rem;
  font-weight: 850;
}

.course-badge {
  color: #005c75;
  background: #dff8ff;
}

.difficulty-beginner {
  color: #0d764c;
  background: #e0f7ec;
}

.difficulty-intermediate {
  color: #7b5500;
  background: #fff0c2;
}

.difficulty-advanced {
  color: #8a2637;
  background: #ffe3e8;
}

.program-card h3 {
  margin-bottom: 10px;
  font-size: 1.32rem;
}

.program-card h3 a {
  text-decoration: none;
}

.program-card h3 a:hover,
.program-card h3 a:focus-visible {
  color: var(--blue);
  text-decoration: underline;
  text-underline-offset: 4px;
}

.card-summary {
  margin-bottom: 15px;
  color: var(--muted);
  font-size: 0.94rem;
}

.concept-list {
  display: flex;
  gap: 7px;
  margin: 0 0 13px;
  padding: 0;
  flex-wrap: wrap;
  list-style: none;
}

.concept-list li,
.meta-chip {
  border: 1px solid #c9dbee;
  color: #355471;
  background: #f4f8fc;
}

.card-feature {
  margin: auto 0 13px;
  color: #5c7390;
  font-size: 0.78rem;
  font-weight: 750;
}

.study-button {
  align-self: flex-start;
  border-color: #1f7dea;
  color: #fff;
  background: var(--blue);
}

.empty-state {
  padding: 64px 20px;
  text-align: center;
}

.empty-state > span {
  color: #8ba5bf;
  font-size: 3rem;
}

.empty-state h3 {
  margin: 6px 0;
  font-size: 1.4rem;
}

.empty-state p {
  color: var(--muted);
}

.empty-state button {
  min-height: 44px;
  padding: 0 15px;
  border: 1px solid #9db8d3;
  border-radius: 8px;
  color: var(--ink);
  background: #fff;
  font-weight: 800;
  cursor: pointer;
}

/* Scalable catalog: featured cards + compact topic directory */
.catalog-filter-bar {
  display: grid;
  grid-template-columns: minmax(260px, 2fr) minmax(180px, 1fr) minmax(180px, 1fr) auto;
  gap: 14px;
  margin-bottom: 22px;
  padding: 18px;
  align-items: end;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: #fff;
  box-shadow: 0 10px 28px rgba(12, 43, 73, 0.08);
}

.filter-field label {
  display: block;
  margin-bottom: 6px;
  color: #294865;
  font-size: 0.82rem;
  font-weight: 850;
}

.catalog-filter-bar .search-control input,
.catalog-filter-bar select {
  width: 100%;
  min-height: 46px;
  border: 1px solid #b9cee3;
  border-radius: 9px;
  color: var(--ink);
  background: #f9fbfe;
  outline: none;
}

.catalog-filter-bar .search-control input {
  padding: 0 12px 0 42px;
}

.catalog-filter-bar select {
  padding: 0 12px;
}

.catalog-filter-bar .search-control input:focus,
.catalog-filter-bar select:focus {
  border-color: var(--blue);
  box-shadow: 0 0 0 3px rgba(23, 105, 223, 0.12);
}

.catalog-filter-bar .clear-filters {
  width: auto;
  min-height: 46px;
  margin: 0;
  padding: 0 17px;
  white-space: nowrap;
}

.featured-programs,
.program-results {
  margin-bottom: 22px;
  padding: clamp(20px, 3vw, 30px);
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--surface);
  box-shadow: var(--shadow);
}

.featured-programs[hidden] {
  display: none;
}

.compact-heading {
  margin-bottom: 18px;
}

.featured-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 14px;
}

.featured-card {
  display: flex;
  min-height: 238px;
  padding: 18px;
  flex-direction: column;
  border: 1px solid #c5d8ea;
  border-radius: 13px;
  background: linear-gradient(180deg, #fff, #f6faff);
  transition: border-color 160ms ease, box-shadow 160ms ease, transform 160ms ease;
}

.featured-card:hover {
  border-color: #86acd2;
  box-shadow: 0 12px 24px rgba(10, 53, 91, 0.09);
  transform: translateY(-2px);
}

.featured-card h3 {
  margin-bottom: 8px;
  font-size: 1.15rem;
}

.featured-card h3 a,
.program-row-content h3 a {
  text-decoration: none;
}

.featured-card h3 a:hover,
.featured-card h3 a:focus-visible,
.program-row-content h3 a:hover,
.program-row-content h3 a:focus-visible {
  color: var(--blue);
  text-decoration: underline;
  text-underline-offset: 4px;
}

.featured-card > p {
  display: -webkit-box;
  margin-bottom: 14px;
  overflow: hidden;
  color: var(--muted);
  font-size: 0.88rem;
  line-height: 1.55;
  -webkit-box-orient: vertical;
  -webkit-line-clamp: 3;
}

.featured-link {
  display: inline-flex;
  margin-top: auto;
  align-items: center;
  gap: 7px;
  color: var(--blue);
  font-size: 0.88rem;
  font-weight: 850;
  text-decoration: none;
}

.featured-link:hover,
.featured-link:focus-visible {
  text-decoration: underline;
  text-underline-offset: 4px;
}

.topic-directory {
  display: grid;
  gap: 12px;
}

.topic-group {
  overflow: hidden;
  border: 1px solid #c7d9eb;
  border-radius: 12px;
  background: #fff;
}

.topic-group summary {
  display: grid;
  min-height: 62px;
  padding: 0 18px;
  grid-template-columns: minmax(0, 1fr) auto 24px;
  gap: 14px;
  align-items: center;
  color: var(--ink);
  background: #f5f9fd;
  cursor: pointer;
  list-style: none;
}

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

.topic-group summary:hover,
.topic-group summary:focus-visible,
.topic-group[open] summary {
  background: #eaf3fc;
}

.topic-name {
  font-size: 1rem;
  font-weight: 900;
}

.topic-count {
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 800;
}

.topic-arrow {
  color: var(--blue);
  font-size: 1.35rem;
  font-weight: 900;
  transition: transform 160ms ease;
}

.topic-group[open] .topic-arrow {
  transform: rotate(180deg);
}

.program-rows {
  border-top: 1px solid #c7d9eb;
}

.program-row {
  display: grid;
  min-height: 72px;
  padding: 10px 16px;
  grid-template-columns: 42px minmax(0, 1fr) auto 78px;
  gap: 12px;
  align-items: center;
  border-bottom: 1px solid #e0ebf5;
}

.program-row:last-child {
  border-bottom: 0;
}

.program-row:hover {
  background: #fbfdff;
}

.program-number {
  color: #6d86a0;
  font-size: 0.78rem;
  font-weight: 900;
  font-variant-numeric: tabular-nums;
}

.program-row-content {
  min-width: 0;
}

.program-row-content h3 {
  margin: 0 0 2px;
  font-size: 0.98rem;
}

.program-row-content p {
  margin: 0;
  overflow: hidden;
  color: var(--muted);
  font-size: 0.76rem;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.row-action {
  color: var(--blue);
  font-size: 0.83rem;
  font-weight: 850;
  text-align: right;
  text-decoration: none;
}

.row-action:hover,
.row-action:focus-visible {
  text-decoration: underline;
  text-underline-offset: 4px;
}

.pagination,
.pagination > div {
  display: flex;
  gap: 7px;
  align-items: center;
  justify-content: center;
}

.pagination {
  margin-top: 22px;
  overflow-x: auto;
}

.pagination[hidden] {
  display: none;
}

.pagination button {
  min-width: 42px;
  min-height: 42px;
  padding: 0 12px;
  border: 1px solid #aec6de;
  border-radius: 8px;
  color: var(--ink);
  background: #fff;
  font-size: 0.82rem;
  font-weight: 850;
  cursor: pointer;
}

.pagination button:hover:not(:disabled),
.pagination button:focus-visible,
.pagination button.is-current {
  border-color: var(--ink);
  color: #fff;
  background: var(--ink);
}

.pagination button:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

/* Program detail page */
.program-main {
  width: min(1500px, calc(100% - 36px));
}

.breadcrumbs {
  display: flex;
  gap: 7px;
  margin-bottom: 18px;
  align-items: center;
  color: var(--muted);
  font-size: 0.88rem;
  flex-wrap: wrap;
}

.breadcrumbs a {
  color: var(--blue);
  font-weight: 750;
  text-decoration: none;
}

.program-page-layout {
  display: grid;
  grid-template-columns: 270px minmax(0, 1fr);
  gap: 22px;
  align-items: start;
}

.example-sidebar {
  position: sticky;
  top: 106px;
  overflow: hidden;
}

.sidebar-title {
  margin: 0;
  padding: 18px 20px;
  border-bottom: 1px solid var(--line);
  font-size: 1.05rem;
}

.example-links {
  display: grid;
  padding: 10px;
}

.example-links a {
  padding: 11px 12px;
  border-radius: 8px;
  color: #3d5875;
  font-size: 0.88rem;
  font-weight: 700;
  text-decoration: none;
}

.example-links a:hover,
.example-links a:focus-visible,
.example-links a.active {
  color: #075fd0;
  background: #dfebff;
}

.sidebar-section {
  padding: 14px 20px 6px;
  color: #7890aa;
  font-size: 0.72rem;
  font-weight: 900;
  letter-spacing: 0.1em;
}

.program-article {
  min-width: 0;
}

.program-hero {
  margin-bottom: 20px;
  padding: clamp(23px, 4vw, 42px);
  border: 1px solid var(--line);
  border-top: 5px solid var(--gold);
  border-radius: 16px;
  background: #fff;
  box-shadow: var(--shadow);
}

.program-hero h1 {
  max-width: 920px;
  font-size: clamp(2rem, 4vw, 3.45rem);
}

.program-hero > p:not(.eyebrow) {
  max-width: 850px;
  margin-bottom: 17px;
  color: var(--muted);
  font-size: 1.02rem;
}

.meta-row,
.knowledge-links,
.code-actions,
.debug-controls,
.call-flow {
  display: flex;
  gap: 9px;
  flex-wrap: wrap;
}

.knowledge-links {
  margin-top: 20px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
}

.knowledge-links > span {
  width: 100%;
  color: var(--muted);
  font-size: 0.82rem;
  font-weight: 800;
}

.knowledge-links a {
  color: var(--blue);
  font-size: 0.88rem;
  font-weight: 750;
  text-underline-offset: 3px;
}

.content-card {
  margin-bottom: 20px;
  padding: clamp(22px, 3vw, 34px);
}

.content-card h2 {
  margin-bottom: 12px;
  font-size: clamp(1.55rem, 3vw, 2.15rem);
}

.content-card h3 {
  margin: 22px 0 8px;
  font-size: 1.18rem;
}

.content-card p,
.content-card li {
  color: #344f6b;
}

.content-card ol,
.content-card ul:not(.concept-list) {
  padding-left: 1.35rem;
}

.info-grid,
.complexity-grid,
.mistake-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 15px;
}

.info-box,
.complexity-box,
.mistake-box {
  padding: 17px;
  border: 1px solid #c8d9ea;
  border-radius: 11px;
  background: #f7fbff;
}

.info-box strong,
.complexity-box strong,
.mistake-box strong {
  display: block;
  margin-bottom: 5px;
  color: var(--ink);
}

.io-code,
.code-window,
.debug-code,
.terminal {
  color: #e9f5ff;
  background: var(--navy-950);
  font-family: "Cascadia Code", "SFMono-Regular", Consolas, monospace;
}

.io-code {
  min-height: 94px;
  margin: 0;
  padding: 17px;
  overflow: auto;
  border-radius: 10px;
  white-space: pre-wrap;
}

.code-window {
  overflow: hidden;
  border: 1px solid #31516f;
  border-radius: 13px;
}

.code-toolbar,
.debug-toolbar {
  display: flex;
  gap: 12px;
  min-height: 62px;
  padding: 10px 14px;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid #294761;
  background: var(--navy-850);
}

.code-toolbar strong,
.debug-toolbar strong {
  color: #fff;
}

.code-actions button,
.code-actions a,
.debug-controls button {
  display: inline-flex;
  min-height: 40px;
  padding: 0 13px;
  align-items: center;
  justify-content: center;
  border: 1px solid #436887;
  border-radius: 8px;
  color: #e7f4ff;
  background: #12314d;
  font: inherit;
  font-size: 0.83rem;
  font-weight: 800;
  text-decoration: none;
  cursor: pointer;
}

.code-actions a,
.debug-controls .next-step,
.debug-controls .start-debug {
  border-color: var(--gold);
  color: #07172a;
  background: var(--gold);
}

.code-actions button:hover,
.code-actions button:focus-visible,
.debug-controls button:hover,
.debug-controls button:focus-visible {
  filter: brightness(1.1);
}

.debug-controls button:disabled {
  cursor: not-allowed;
  filter: none;
  opacity: 0.45;
}

.source-code {
  display: block;
  margin: 0;
  padding: 20px;
  overflow-x: auto;
  color: #e9f5ff;
  font-family: "Cascadia Code", "SFMono-Regular", Consolas, monospace;
  font-size: 0.91rem;
  line-height: 1.72;
  white-space: pre;
}

.source-code .preprocessor { color: #d58cff; }
.source-code .type { color: #5ed7ff; }
.source-code .string { color: #d9ef60; }
.source-code .number { color: #ffb95a; }
.source-code .comment { color: #7892a8; }

.debug-lab {
  margin-bottom: 20px;
  overflow: hidden;
  color: #dceeff;
  background: var(--navy-900);
}

.debug-toolbar {
  min-height: 76px;
  padding: 13px 18px;
}

.debug-title p {
  margin: 0;
  color: #8eb2d2;
  font-size: 0.78rem;
}

.debug-inputs {
  display: flex;
  gap: 10px;
  padding: 15px 18px;
  align-items: end;
  border-bottom: 1px solid #294761;
  background: #0a2239;
}

.debug-inputs label {
  display: grid;
  gap: 5px;
  color: #b9d3e9;
  font-size: 0.78rem;
  font-weight: 800;
}

.debug-inputs input {
  width: 120px;
  min-height: 42px;
  padding: 0 11px;
  border: 1px solid #436887;
  border-radius: 8px;
  color: #fff;
  background: #041522;
  outline: none;
}

.debug-inputs input:focus {
  border-color: var(--cyan);
  box-shadow: 0 0 0 3px rgba(24, 201, 236, 0.12);
}

.input-error {
  margin: 0 0 8px;
  color: #ff9ba7;
  font-size: 0.8rem;
  font-weight: 750;
}

.debug-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.35fr) minmax(320px, 0.65fr);
  min-height: 530px;
}

.debug-code {
  min-width: 0;
  padding: 14px 0;
  overflow: auto;
  border-right: 1px solid #294761;
}

.code-line {
  display: grid;
  grid-template-columns: 54px minmax(max-content, 1fr);
  min-height: 28px;
  padding-right: 15px;
  align-items: center;
  color: #dbeaff;
  font-size: 0.86rem;
  line-height: 1.55;
  white-space: pre;
}

.code-line .line-number {
  padding-right: 13px;
  color: #64839f;
  text-align: right;
  user-select: none;
}

.code-line.is-active {
  color: #fff;
  background: #113757;
  box-shadow: inset 4px 0 0 var(--gold);
}

.code-line.is-active .line-number {
  color: var(--gold);
  font-weight: 900;
}

.debug-state {
  display: grid;
  grid-template-rows: auto auto auto minmax(130px, 1fr);
  min-width: 0;
}

.state-panel {
  padding: 15px 17px;
  border-bottom: 1px solid #294761;
}

.state-panel h3 {
  margin: 0 0 9px;
  color: #68dfff;
  font-size: 0.76rem;
  letter-spacing: 0.08em;
}

.step-message {
  margin: 0;
  color: #e8f4ff;
  font-size: 0.9rem;
  line-height: 1.55;
}

.variable-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.8rem;
}

.variable-table th,
.variable-table td {
  padding: 6px 8px;
  border: 1px solid #294761;
  text-align: left;
}

.variable-table th {
  color: #88a8c4;
  background: #0a2239;
}

.variable-table td {
  color: #fff;
}

.call-flow {
  gap: 6px;
}

.call-chip {
  display: inline-flex;
  min-height: 28px;
  padding: 3px 8px;
  align-items: center;
  border: 1px solid #416583;
  border-radius: 7px;
  color: #dceeff;
  background: #12314d;
  font-family: "Cascadia Code", Consolas, monospace;
  font-size: 0.74rem;
}

.terminal {
  min-height: 100%;
  margin: 0;
  padding: 14px 16px;
  overflow: auto;
  color: #d8f6df;
  font-size: 0.84rem;
  line-height: 1.55;
  white-space: pre-wrap;
}

.progress-row {
  display: flex;
  min-height: 48px;
  padding: 9px 18px;
  align-items: center;
  gap: 12px;
  border-top: 1px solid #294761;
  background: #0a2239;
}

.progress-row progress {
  width: 100%;
  height: 9px;
  accent-color: var(--gold);
}

.progress-row span {
  flex: 0 0 auto;
  color: #9ebbd3;
  font-size: 0.78rem;
  font-weight: 800;
}

.mistake-box {
  border-left: 4px solid var(--red);
}

.challenge-box {
  padding: 20px;
  border: 1px solid #b8a5ec;
  border-radius: 12px;
  background: #f4f0ff;
}

.challenge-box strong {
  color: #4d348f;
}

.tour-state {
  grid-template-rows: auto auto minmax(180px, 1fr);
}

.tour-selected-line {
  color: #d9ef60;
  font-family: "Cascadia Code", "SFMono-Regular", Consolas, monospace;
  font-size: 0.82rem;
  overflow-wrap: anywhere;
}

.tour-output-panel {
  min-height: 0;
  border-bottom: 0;
}

.program-navigation {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
  margin-bottom: 20px;
}

.program-navigation a {
  display: grid;
  min-height: 86px;
  padding: 16px 18px;
  align-content: center;
  border: 1px solid var(--line);
  border-radius: 12px;
  color: var(--ink);
  background: #fff;
  box-shadow: 0 10px 24px rgba(12, 43, 73, 0.07);
  text-decoration: none;
}

.program-navigation a:hover,
.program-navigation a:focus-visible {
  border-color: #82abd2;
  background: #f6faff;
}

.program-navigation span {
  color: var(--blue);
  font-size: 0.76rem;
  font-weight: 850;
}

.program-navigation strong {
  margin-top: 3px;
  font-size: 0.9rem;
}

.program-navigation .next-program {
  text-align: right;
}

.mobile-example-menu {
  display: none;
  margin-bottom: 16px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: #fff;
}

.mobile-example-menu summary {
  padding: 13px 15px;
  font-weight: 800;
  cursor: pointer;
}

.mobile-example-menu nav {
  display: grid;
  padding: 0 10px 10px;
}

.mobile-example-menu a {
  padding: 10px;
  color: var(--blue);
  font-weight: 700;
  text-decoration: none;
}

.toast {
  position: fixed;
  z-index: 30000;
  right: 20px;
  bottom: 20px;
  max-width: min(360px, calc(100vw - 40px));
  padding: 12px 16px;
  border: 1px solid #4a6d8b;
  border-radius: 9px;
  color: #fff;
  background: var(--navy-850);
  box-shadow: 0 16px 36px rgba(0, 7, 18, 0.35);
  font-weight: 750;
}

.site-footer {
  display: grid;
  grid-template-columns: 1fr auto auto;
  gap: 34px;
  min-height: 190px;
  padding: 38px clamp(24px, 6vw, 90px);
  align-items: center;
  border-top: 2px solid var(--gold);
  color: #b9d0e5;
  background: var(--navy-950);
}

.footer-brand {
  color: #c9e1f8;
  font-family: Georgia, "Times New Roman", serif;
  font-size: 1.8rem;
  font-weight: 800;
  text-decoration: none;
}

.site-footer p {
  margin: 4px 0 0;
  font-size: 0.87rem;
}

.site-footer nav {
  display: flex;
  gap: 18px;
}

.site-footer nav a {
  color: #cde0f2;
  font-size: 0.87rem;
  font-weight: 750;
  text-decoration: none;
}

@media (max-width: 1080px) {
  .desktop-nav {
    display: none;
  }

  .mobile-nav {
    display: block;
  }

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

  .catalog-filter-bar {
    grid-template-columns: minmax(240px, 2fr) minmax(170px, 1fr) minmax(170px, 1fr);
  }

  .catalog-filter-bar .clear-filters {
    grid-column: 1 / -1;
    justify-self: end;
  }

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

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

  .debug-code {
    max-height: 520px;
    border-right: 0;
    border-bottom: 1px solid #294761;
  }

  .debug-state {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    grid-template-rows: auto auto;
  }

  .state-panel {
    border-right: 1px solid #294761;
  }
}

@media (max-width: 820px) {
  main,
  .program-main {
    width: min(100% - 24px, 760px);
    padding-top: 22px;
  }

  .catalog-heading {
    align-items: flex-start;
    flex-direction: column;
  }

  .catalog-layout,
  .program-page-layout {
    grid-template-columns: 1fr;
  }

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

  .catalog-filter-bar .search-field {
    grid-column: 1 / -1;
  }

  .catalog-filter-bar .clear-filters {
    grid-column: 1 / -1;
    justify-self: stretch;
  }

  .filter-panel,
  .example-sidebar {
    display: none;
  }

  .mobile-filter-panel,
  .mobile-example-menu {
    display: block;
  }

  .mobile-filter-panel {
    margin-bottom: 14px;
    border: 1px solid var(--line);
    border-radius: 10px;
    background: #fff;
  }

  .mobile-filter-panel summary {
    padding: 13px 15px;
    font-weight: 800;
    cursor: pointer;
  }

  .mobile-filter-slot .filter-panel-inner {
    position: static;
    padding-top: 6px;
  }

  .info-grid,
  .complexity-grid,
  .mistake-grid {
    grid-template-columns: 1fr;
  }

  .site-footer {
    grid-template-columns: 1fr;
    gap: 18px;
    text-align: center;
  }

  .site-footer nav {
    justify-content: center;
    flex-wrap: wrap;
  }
}

@media (max-width: 620px) {
  .site-header {
    min-height: 70px;
    padding: 0 13px;
  }

  .brand {
    gap: 9px;
  }

  .brand img {
    width: 49px;
    height: 49px;
  }

  .brand > span {
    font-size: 1.48rem;
  }

  .catalog-filter-bar {
    grid-template-columns: 1fr;
    padding: 14px;
  }

  .catalog-filter-bar .search-field,
  .catalog-filter-bar .clear-filters {
    grid-column: auto;
  }

  .featured-programs,
  .program-results {
    padding: 16px;
  }

  .featured-grid {
    display: flex;
    margin-right: -16px;
    margin-left: -2px;
    padding-right: 16px;
    padding-bottom: 8px;
    overflow-x: auto;
    scroll-snap-type: x mandatory;
  }

  .featured-card {
    min-width: min(82vw, 330px);
    min-height: 226px;
    scroll-snap-align: start;
  }

  .program-row {
    grid-template-columns: 34px minmax(0, 1fr) auto;
    gap: 8px;
  }

  .program-row .difficulty {
    grid-column: 2;
    justify-self: start;
  }

  .row-action {
    grid-column: 3;
    grid-row: 1 / span 2;
  }

  .topic-group summary {
    padding: 0 13px;
    grid-template-columns: minmax(0, 1fr) auto 18px;
    gap: 8px;
  }

  .topic-count {
    font-size: 0.7rem;
  }

  .pagination {
    justify-content: flex-start;
  }

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

  .program-navigation .next-program {
    text-align: left;
  }

  .tour-state {
    grid-template-columns: 1fr;
    grid-template-rows: auto auto minmax(160px, 1fr);
  }

  h1,
  .program-hero h1 {
    font-size: 2.15rem;
  }

  .program-results,
  .content-card,
  .program-hero {
    padding: 19px;
    border-radius: 12px;
  }

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

  .debug-toolbar,
  .code-toolbar {
    align-items: flex-start;
    flex-direction: column;
  }

  .debug-inputs {
    align-items: stretch;
    flex-direction: column;
  }

  .debug-inputs input {
    width: 100%;
  }

  .debug-controls,
  .code-actions {
    width: 100%;
  }

  .debug-controls button,
  .code-actions button,
  .code-actions a {
    flex: 1 1 auto;
  }

  .debug-state {
    grid-template-columns: 1fr;
  }

  .state-panel {
    border-right: 0;
  }

  .source-code {
    font-size: 0.8rem;
  }

  .site-footer {
    padding: 34px 18px;
  }
}

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