:root {
  --bg: #0b1220;
  --surface: #121a2b;
  --surface-soft: #17233b;
  --muted: #a0aec6;
  --text: #e8eefc;
  --primary: #81a8ff;
  --primary-soft: #21345d;
  --border: #25314f;
  --shadow: 0 12px 28px rgba(0, 0, 0, 0.35);
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
}

body {
  font-family: Inter, "Segoe UI", Roboto, sans-serif;
  color: var(--text);
  background: radial-gradient(circle at top, #16233f 0%, var(--bg) 45%);
  line-height: 1.7;
}

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

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.75rem 1.5rem;
  background: rgba(8, 13, 24, 0.92);
  backdrop-filter: blur(6px);
  color: #fff;
  border-bottom: 1px solid var(--border);
}

.brand {
  display: flex;
  gap: 0.75rem;
  align-items: center;
}

.brand__logo {
  font-size: 1.5rem;
}

.brand__title {
  margin: 0;
  font-weight: 700;
}

.brand__subtitle {
  margin: 0;
  font-size: 0.8rem;
  color: #b8c8ec;
}

.topnav a {
  color: #e9efff;
  text-decoration: none;
  margin-left: 1rem;
  font-size: 0.95rem;
}

.layout {
  display: grid;
  grid-template-columns: 260px 1fr;
  gap: 1.25rem;
  max-width: 1200px;
  margin: 1rem auto;
  padding: 0 1rem;
}

.sidebar {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 1rem;
  height: fit-content;
  position: sticky;
  top: 5rem;
  box-shadow: var(--shadow);
}

.sidebar__heading {
  margin-top: 0;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
}

.sidebar ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.sidebar li + li {
  margin-top: 0.7rem;
}

.sidebar a {
  text-decoration: none;
  color: var(--primary);
  font-weight: 500;
}

main {
  display: grid;
  gap: 1rem;
}

.hero,
.section,
.article {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 1.25rem;
  box-shadow: var(--shadow);
}

.hero__kicker {
  margin: 0;
  color: var(--primary);
  font-weight: 600;
}

h1 {
  margin: 0.5rem 0 0.75rem;
  font-size: clamp(1.6rem, 3vw, 2.3rem);
  line-height: 1.25;
}

h2 {
  margin-top: 0;
  font-size: 1.4rem;
}

h3 {
  line-height: 1.3;
}

.hero__actions {
  display: flex;
  gap: 0.75rem;
  margin-top: 1rem;
  flex-wrap: wrap;
}

.btn {
  display: inline-block;
  padding: 0.55rem 1rem;
  border-radius: 0.6rem;
  border: 1px solid var(--border);
  text-decoration: none;
  color: var(--text);
  font-weight: 600;
  background: var(--surface-soft);
}

.btn--primary {
  background: var(--primary);
  color: #081126;
  border-color: var(--primary);
}

.cards {
  display: grid;
  gap: 0.9rem;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}

.card {
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 1rem;
  background: linear-gradient(180deg, var(--surface), var(--surface-soft));
}

.card__tag {
  display: inline-block;
  margin: 0;
  color: #b9ceff;
  background: var(--primary-soft);
  border-radius: 999px;
  padding: 0.1rem 0.6rem;
  font-size: 0.8rem;
}

.card h3 {
  margin-bottom: 0.4rem;
}

.card a,
.resource {
  color: #aac3ff;
  text-decoration: none;
  font-weight: 600;
}

.section--muted {
  background: #0f1728;
}

.track-list {
  margin: 0;
  padding-left: 1.1rem;
}

.resource-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 0.7rem;
  margin-top: 1rem;
}

.resource {
  border: 1px dashed var(--border);
  border-radius: 0.6rem;
  padding: 0.7rem;
  background: #0f1728;
}

.footer {
  text-align: center;
  color: var(--muted);
  font-size: 0.9rem;
  padding: 2rem 1rem;
}

.page {
  max-width: 860px;
  margin: 1rem auto 2rem;
  padding: 0 1rem;
}

.breadcrumb {
  color: var(--muted);
  margin-bottom: 0.75rem;
}

.breadcrumb a {
  color: var(--muted);
  text-decoration: none;
}

.meta {
  color: var(--muted);
  font-size: 0.92rem;
}

.callout {
  border-left: 4px solid #7aa5ff;
  padding: 0.8rem 1rem;
  background: #111f37;
  border-radius: 0.45rem;
}

.article pre {
  padding: 0.85rem;
  border-radius: 0.5rem;
  background: #09101d;
  overflow-x: auto;
  border: 1px solid var(--border);
}

.article code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  font-size: 0.95em;
}

@media (max-width: 900px) {
  .layout {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
  }

  .topbar {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.75rem;
  }

  .topnav a {
    margin-left: 0;
    margin-right: 1rem;
  }
}