:root {
  --navy: #101e37;
  --blue: #174b8a;
  --ink: #1b2a3d;
  --muted: #526277;
  --line: #dce4ee;
  --soft: #f3f7fc;
  --gold: #d9a441;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  font: 16px/1.7 system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: #fff;
}

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

a:hover {
  text-decoration-thickness: 2px;
}

.skip-link {
  position: absolute;
  top: -100px;
  left: 1rem;
  background: #fff;
  padding: .5rem;
  z-index: 10;
}

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

.site-header {
  background: var(--navy);
  color: #fff;
}

.header-inner {
  max-width: 1340px;
  margin: auto;
  min-height: 76px;
  padding: 0 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 2rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  color: #fff;
  text-decoration: none;
  font-size: 1.1rem;
}

.gt-logo {
  display: block;
  width: auto;
  height: 38px;
  flex-shrink: 0;
}

.brand-title {
  border-left: 1px solid #8291a8;
  padding-left: 1.25rem;
}

.top-nav {
  display: flex;
  gap: 1.7rem;
}

.top-nav a {
  color: #e6edf8;
  text-decoration: none;
  font-size: .94rem;
}

.top-nav a:hover {
  text-decoration: underline;
}

.page-shell {
  max-width: 1340px;
  margin: auto;
  display: grid;
  grid-template-columns: 240px minmax(0, 1fr);
  gap: 4rem;
  padding: 2.8rem 2rem 5rem;
}

.sidebar {
  border-right: 1px solid var(--line);
  padding-right: 1.5rem;
}

.sidebar-label {
  font-size: .72rem;
  letter-spacing: .14em;
  font-weight: 800;
  color: var(--muted);
  margin: 0 0 .7rem;
}

.sidebar-secondary {
  margin-top: 2rem;
}

.sidebar a {
  display: block;
  padding: .48rem .65rem;
  margin-left: -.65rem;
  border-radius: 6px;
  color: var(--ink);
  text-decoration: none;
  font-size: .92rem;
}

.sidebar a:hover,.sidebar a:focus {
  background: var(--soft);
}

.sidebar a span {
  margin-left: .45rem;
}

.content {
  max-width: 840px;
  min-width: 0;
}

.content h1 {
  font-size: clamp(2rem, 3.5vw, 3rem);
  line-height: 1.15;
  letter-spacing: -.035em;
  color: var(--navy);
  margin: 0 0 1.1rem;
}

.content h2 {
  font-size: 1.55rem;
  line-height: 1.25;
  color: var(--navy);
  margin: 2.5rem 0 .8rem;
}

.content h3 {
  color: var(--navy);
  margin-top: 2rem;
}

.content p,.content li {
  max-width: 76ch;
}

.content img {
  max-width: 100%;
  height: auto;
  border: 1px solid var(--line);
  border-radius: 7px;
}

.content pre {
  overflow: auto;
  background: #17263d;
  color: #f5f7fb;
  padding: 1rem 1.2rem;
  border-radius: 8px;
}

.content code {
  font-size: .9em;
}

.content :not(pre)>code {
  background: var(--soft);
  padding: .12rem .3rem;
  border-radius: 4px;
}

.content table {
  display: block;
  overflow-x: auto;
  border-collapse: collapse;
  width: 100%;
  font-size: .94rem;
}

.content th,.content td {
  padding: .65rem .8rem;
  border: 1px solid var(--line);
  vertical-align: top;
}

.content th {
  background: var(--soft);
  text-align: left;
}

.content blockquote {
  margin: 1.5rem 0;
  padding: .3rem 1.2rem;
  border-left: 4px solid var(--gold);
  background: #fffbf1;
  color: #3c4755;
}

.callout {
  background: #eaf3ff;
  border-left: 4px solid var(--blue);
  padding: 1rem 1.25rem;
  border-radius: 0 7px 7px 0;
  margin: 1.7rem 0;
}

.module-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
  margin: 1.5rem 0;
}

.module-card {
  display: flex;
  flex-direction: column;
  gap: .4rem;
  padding: 1.35rem;
  border: 1px solid var(--line);
  border-radius: 10px;
  color: var(--ink);
  text-decoration: none;
  box-shadow: 0 3px 12px #17263d08;
}

.module-card:hover {
  border-color: var(--blue);
  box-shadow: 0 7px 18px #17263d16;
}

.module-card strong {
  font-size: 1.15rem;
  color: var(--navy);
}

.module-card small {
  color: var(--muted);
  margin-top: auto;
}

.module-number {
  color: var(--blue);
  font-size: .8rem;
  font-weight: 800;
  letter-spacing: .12em;
}

.site-footer {
  border-top: 1px solid var(--line);
  max-width: 1340px;
  margin: auto;
  padding: 1.7rem 2rem;
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  color: var(--muted);
  font-size: .85rem;
}

@media(max-width:800px) {
  .header-inner {
    padding: 1rem;
    align-items: flex-start;
    flex-direction: column;
    gap: .5rem;
  }

  .top-nav {
    gap: 1rem;
    flex-wrap: wrap;
  }

  .page-shell {
    display: block;
    padding: 1.5rem 1rem 3rem;
  }

  .sidebar {
    border-right: 0;
    border-bottom: 1px solid var(--line);
    padding: 0 0 1rem;
    margin-bottom: 2rem;
  }

  .sidebar a {
    display: inline-block;
    margin: 0 .3rem .3rem 0;
  }

  .sidebar-secondary {
    margin-top: 1rem;
  }

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

  .site-footer {
    padding: 1.5rem 1rem;
    flex-direction: column;
  }

}

@media(max-width:560px) {
  .brand {
    align-items: flex-start;
    flex-direction: column;
    gap: .55rem;
  }

  .gt-logo {
    height: 32px;
  }

  .brand-title {
    border-left: 0;
    border-top: 1px solid #8291a8;
    padding: .55rem 0 0;
  }
}