:root {
  --bg: #f5f7fb;
  --surface: #ffffff;
  --surface-2: #f8fafc;
  --text: #172033;
  --muted: #667085;
  --line: #dfe5ef;
  --ink: #101828;
  --blue: #2563eb;
  --blue-dark: #1d4ed8;
  --green: #0f766e;
  --amber: #b45309;
  --code: #111827;
  --radius: 8px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: Arial, sans-serif;
  font-size: 16px;
  line-height: 1.58;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

a {
  color: var(--blue);
  text-decoration: none;
}

a:hover {
  color: var(--blue-dark);
  text-decoration: underline;
}

.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 28px 22px 34px;
  background: var(--surface);
  min-height: 100vh;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  display: grid;
  grid-template-columns: auto minmax(260px, 520px) auto;
  gap: 18px;
  align-items: center;
  padding: 12px 24px;
  border-bottom: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(12px);
}

.site-brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--ink);
  font-weight: 700;
}

.site-brand:hover {
  color: var(--ink);
  text-decoration: none;
}

.site-brand-mark {
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  border-radius: var(--radius);
  background: var(--ink);
  color: #ffffff;
  font-size: 12px;
}

.site-brand-text {
  white-space: nowrap;
}

.site-search,
.search-page-form {
  display: flex;
  align-items: center;
  gap: 8px;
}

.site-search input,
.search-page-form input {
  width: 100%;
  min-height: 40px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 0 12px;
  background: #ffffff;
  color: var(--text);
  font: inherit;
}

.site-search button,
.search-page-form button {
  min-height: 40px;
  border: 0;
  border-radius: var(--radius);
  padding: 0 14px;
  background: var(--blue);
  color: #ffffff;
  font-weight: 700;
  cursor: pointer;
}

.site-search button:hover,
.search-page-form button:hover {
  background: var(--blue-dark);
}

.site-nav {
  display: flex;
  justify-content: flex-end;
  flex-wrap: wrap;
  gap: 14px;
  font-size: 14px;
}

.site-nav a {
  color: #344054;
}

.breadcrumbs {
  display: flex;
  flex-wrap: wrap;
  gap: 7px;
  align-items: center;
  margin: 0 0 22px;
  color: var(--muted);
  font-size: 13px;
}

.breadcrumbs a {
  color: #475467;
}

.breadcrumbs span:last-child {
  color: var(--ink);
}

h1 {
  font-size: 32px;
  line-height: 1.2;
  margin: 0 0 16px;
  letter-spacing: 0;
}

h2 {
  font-size: 22px;
  line-height: 1.25;
  margin: 30px 0 12px;
  letter-spacing: 0;
}

h3 {
  font-size: 18px;
  margin: 22px 0 8px;
  letter-spacing: 0;
}

.meta {
  color: var(--muted);
  font-size: 14px;
}

.card {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px;
  margin: 16px 0;
  background: var(--surface-2);
}

pre {
  background: var(--code);
  color: #f9fafb;
  padding: 16px;
  border-radius: var(--radius);
  overflow: auto;
  font-size: 14px;
  line-height: 1.45;
}

code {
  font-family: Consolas, "Courier New", monospace;
}

.line-explain {
  border-left: 3px solid var(--line);
  padding-left: 12px;
  margin: 8px 0;
}

.nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin: 28px 0;
  padding: 16px;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.nav a {
  color: var(--blue);
  text-decoration: none;
}

.lesson-list li {
  margin: 6px 0;
}

.badge {
  display: inline-block;
  background: #eef4ff;
  color: #1d4ed8;
  padding: 3px 8px;
  border-radius: 999px;
  font-size: 12px;
  margin-right: 6px;
}

.notice {
  background: #fff8ed;
  border: 1px solid #fed7aa;
  border-radius: var(--radius);
  padding: 14px;
}

.footer {
  color: var(--muted);
  font-size: 13px;
  margin-top: 40px;
  border-top: 1px solid var(--line);
  padding-top: 20px;
}

.home-page {
  background: #f4f7fb;
}

.topbar {
  max-width: 1180px;
  margin: 0 auto;
  padding: 22px 24px 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--ink);
  font-weight: 700;
}

.brand:hover {
  text-decoration: none;
  color: var(--ink);
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 38px;
  height: 38px;
  border-radius: var(--radius);
  background: var(--ink);
  color: #ffffff;
  font-size: 13px;
  letter-spacing: 0;
}

.topnav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: flex-end;
  gap: 8px 18px;
  font-size: 14px;
}

.topnav a {
  color: #344054;
}

.hero {
  max-width: 1180px;
  margin: 28px auto 0;
  padding: 50px 24px 36px;
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(320px, 0.95fr);
  gap: 34px;
  align-items: center;
}

.hero-copy {
  max-width: 690px;
}

.eyebrow {
  margin: 0 0 10px;
  color: var(--green);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0;
  text-transform: uppercase;
}

.hero h1 {
  margin: 0 0 16px;
  color: var(--ink);
  font-size: clamp(34px, 5vw, 58px);
  line-height: 1.03;
  letter-spacing: 0;
}

.lead {
  margin: 0;
  max-width: 650px;
  color: #475467;
  font-size: 19px;
  line-height: 1.55;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 26px;
}

.button-primary,
.button-secondary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 0 18px;
  border-radius: var(--radius);
  font-weight: 700;
}

.button-primary {
  background: var(--blue);
  color: #ffffff;
}

.button-primary:hover {
  background: var(--blue-dark);
  color: #ffffff;
  text-decoration: none;
}

.button-secondary {
  border: 1px solid var(--line);
  background: #ffffff;
  color: var(--ink);
}

.button-secondary:hover {
  color: var(--ink);
  text-decoration: none;
  border-color: #b7c2d5;
}

.data-panel {
  border: 1px solid #1f2937;
  border-radius: var(--radius);
  background: #0b1220;
  color: #e5e7eb;
  overflow: hidden;
  box-shadow: 0 24px 60px rgba(15, 23, 42, 0.22);
}

.panel-tabs {
  display: flex;
  gap: 7px;
  padding: 14px 16px;
  background: #151f31;
  border-bottom: 1px solid #273449;
}

.panel-tabs span {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: #ef4444;
}

.panel-tabs span:nth-child(2) {
  background: #f59e0b;
}

.panel-tabs span:nth-child(3) {
  background: #10b981;
}

.data-panel pre {
  margin: 0;
  border-radius: 0;
  background: transparent;
  color: #dbeafe;
  padding: 18px;
}

.data-panel p {
  margin: 0;
  padding: 0 18px 18px;
  color: #b6c2d4;
  font-size: 14px;
}

.stats-grid,
.content-band,
.path-section,
.home-footer {
  max-width: 1180px;
  margin-left: auto;
  margin-right: auto;
  padding-left: 24px;
  padding-right: 24px;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 14px;
  margin-top: 10px;
}

.stat-card {
  background: #ffffff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px;
}

.stat-card strong {
  display: block;
  color: var(--ink);
  font-size: 25px;
  line-height: 1.1;
}

.stat-card span {
  display: block;
  margin-top: 7px;
  color: var(--muted);
  font-size: 14px;
}

.search-page-form {
  max-width: 720px;
  margin: 24px 0;
}

.search-summary {
  color: var(--muted);
  margin: 10px 0 18px;
}

.search-results {
  display: grid;
  gap: 12px;
}

.search-result {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px;
  background: var(--surface-2);
}

.search-result span {
  display: inline-block;
  margin-bottom: 6px;
  color: var(--green);
  font-size: 12px;
  font-weight: 700;
}

.search-result h2 {
  margin: 0;
  font-size: 18px;
}

.search-result p {
  margin: 8px 0 0;
  color: var(--muted);
}

.content-band {
  display: grid;
  grid-template-columns: minmax(0, 0.95fr) minmax(0, 1.05fr);
  gap: 28px;
  margin-top: 42px;
  padding-top: 34px;
  padding-bottom: 34px;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.content-band h2,
.section-heading h2 {
  margin-top: 0;
  color: var(--ink);
  font-size: 28px;
}

.content-band p {
  color: #475467;
}

.feature-list {
  display: grid;
  gap: 12px;
}

.feature-list article,
.path-grid a {
  background: #ffffff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px;
}

.feature-list h3 {
  margin-top: 0;
  color: var(--ink);
}

.feature-list p {
  margin-bottom: 0;
}

.path-section {
  margin-top: 38px;
  padding-bottom: 34px;
}

.section-heading {
  max-width: 700px;
}

.path-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 14px;
  margin-top: 18px;
}

.path-grid a {
  color: var(--text);
}

.path-grid a:hover {
  border-color: #b7c2d5;
  text-decoration: none;
}

.path-grid span {
  display: inline-block;
  margin-bottom: 16px;
  color: var(--amber);
  font-weight: 700;
}

.path-grid strong {
  display: block;
  color: var(--ink);
  font-size: 18px;
}

.path-grid p {
  margin: 8px 0 0;
  color: var(--muted);
  font-size: 14px;
}

.home-footer {
  display: flex;
  flex-wrap: wrap;
  gap: 14px 20px;
  align-items: center;
  justify-content: space-between;
  padding-top: 24px;
  padding-bottom: 30px;
  color: var(--muted);
  font-size: 14px;
}

@media (max-width: 860px) {
  .site-header {
    grid-template-columns: 1fr;
    gap: 10px;
  }

  .site-search {
    width: 100%;
  }

  .site-nav {
    justify-content: flex-start;
  }

  .topbar,
  .hero,
  .content-band {
    grid-template-columns: 1fr;
  }

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

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

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

@media (max-width: 560px) {
  .container {
    padding: 26px 16px;
  }

  .hero {
    padding-top: 34px;
  }

  .hero h1 {
    font-size: 34px;
  }

  .lead {
    font-size: 17px;
  }

  .stats-grid,
  .path-grid {
    grid-template-columns: 1fr;
  }

  .nav {
    flex-direction: column;
  }
}