*,
*::before,
*::after {
  box-sizing: border-box;
}

:root {
  color-scheme: light;
  font-family: "Inter", "Segoe UI", system-ui, -apple-system, sans-serif;
  line-height: 1.6;
  --bg-start: #f4f7ff;
  --bg-end: #e0ecff;
  --card-bg: #ffffff;
  --card-border: rgba(15, 32, 62, 0.08);
  --text-dark: #1e1f24;
  --text-muted: #4d5566;
  --accent: #195efc;
  --muted-bg: rgba(25, 94, 252, 0.08);
}

html,
body {
  margin: 0;
  padding: 0;
  min-height: 100%;
  background: linear-gradient(160deg, var(--bg-start), var(--bg-end));
  color: var(--text-dark);
}

body {
  display: flex;
  flex-direction: column;
}

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

a:hover,
a:focus-visible {
  text-decoration: underline;
}

.site-header {
  backdrop-filter: blur(12px);
  background-color: rgba(255, 255, 255, 0.8);
  border-bottom: 1px solid var(--card-border);
  padding: 1rem 2rem;
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-weight: 700;
  font-size: 1.1rem;
  letter-spacing: 0.02em;
}

.primary-nav {
  display: flex;
  gap: 1.25rem;
  font-size: 0.95rem;
}

.page {
  width: 100%;
  max-width: 1100px;
  margin: 2.5rem auto;
  padding: 0 1.5rem;
  flex: 1;
}

.hero-card {
  max-width: 860px;
  margin: 0 auto 2rem;
  padding: 2.75rem 3rem;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 28px;
  box-shadow: 0 30px 70px rgba(15, 32, 62, 0.1);
  text-align: center;
}

.eyebrow {
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: var(--text-muted);
  font-size: 0.85rem;
  margin: 0 0 1rem;
}

.hero-card h1 {
  margin: 0;
  font-size: clamp(2rem, 4vw, 2.8rem);
}

.hero-subtitle {
  margin: 0.75rem 0 0;
  color: var(--text-muted);
  font-size: 1rem;
}

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

.content-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 24px;
  padding: 2.5rem 3rem;
  max-width: 860px;
  margin: 0 auto;
  box-shadow: 0 24px 55px rgba(15, 32, 62, 0.08);
}

.content-card section + section {
  margin-top: 2.5rem;
}

.section-heading {
  margin-top: 0;
  margin-bottom: 0.75rem;
  font-size: 1.35rem;
  line-height: 1.3;
}

.subheading {
  font-weight: 600;
  margin: 1.5rem 0 0.75rem;
}

.section-nav {
  position: sticky;
  top: 6rem;
  align-self: start;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 18px;
  padding: 1.5rem;
  max-height: calc(100vh - 8rem);
  overflow-y: auto;
  box-shadow: 0 18px 40px rgba(15, 32, 62, 0.08);
}

.section-nav h3 {
  margin-top: 0;
  font-size: 1rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
}

.section-nav ol {
  list-style: none;
  padding: 0;
  margin: 1rem 0 0;
  display: flex;
  flex-direction: column;
  gap: 0.45rem;
}

.section-nav a {
  color: var(--text-dark);
  font-size: 0.95rem;
  border-radius: 999px;
  padding: 0.35rem 0.75rem;
  display: inline-block;
}

.section-nav a:hover,
.section-nav a:focus-visible {
  background: var(--muted-bg);
}

footer {
  text-align: center;
  padding: 2rem 1rem 3rem;
  color: var(--text-muted);
  font-size: 0.9rem;
}

@media (min-width: 1100px) {
  .layout {
    grid-template-columns: minmax(0, 860px) 220px;
    align-items: flex-start;
  }

  .content-card {
    margin: 0;
  }
}

@media (max-width: 700px) {
  .site-header {
    flex-direction: column;
    gap: 0.75rem;
  }

  .hero-card,
  .content-card {
    padding: 1.75rem 1.5rem;
  }
}