:root {
  --bg: #f7f9fc;
  --ink: #122033;
  --muted: #5e6b7a;
  --card: #ffffff;
  --line: #d9e2ef;
  --brand: #2457ff;
  --brand2: #0b2463;
  --soft: #edf3ff;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.65;
}
a { color: var(--brand); text-decoration: none; }
a:hover { text-decoration: underline; }
.container { max-width: 1120px; margin: 0 auto; padding: 0 22px; }
.site-header {
  background: #fff;
  border-bottom: 1px solid var(--line);
  position: sticky;
  top: 0;
  z-index: 5;
}
.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 68px;
  gap: 20px;
}
.logo {
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--brand2);
}
.nav-links { display: flex; gap: 18px; flex-wrap: wrap; font-size: 14px; }
.hero {
  padding: 72px 0 44px;
  background: linear-gradient(180deg, #ffffff 0%, #eef4ff 100%);
  border-bottom: 1px solid var(--line);
}
.kicker {
  display: inline-flex;
  padding: 6px 12px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--brand2);
  background: white;
  font-size: 14px;
  font-weight: 700;
}
h1 {
  max-width: 820px;
  margin: 18px 0 18px;
  font-size: clamp(38px, 5vw, 62px);
  line-height: 1.02;
  letter-spacing: -0.055em;
}
.lead { max-width: 780px; font-size: 20px; color: var(--muted); }
.cta-row { display: flex; gap: 14px; flex-wrap: wrap; margin-top: 28px; }
.btn {
  display: inline-block;
  padding: 13px 18px;
  border-radius: 12px;
  background: var(--brand);
  color: #fff;
  font-weight: 800;
  box-shadow: 0 8px 22px rgba(36,87,255,0.22);
}
.btn.secondary {
  background: white;
  color: var(--brand2);
  box-shadow: none;
  border: 1px solid var(--line);
}
.main {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 320px;
  gap: 36px;
  padding: 46px 0;
}
.article-card, .side-card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 22px;
  padding: 30px;
  box-shadow: 0 10px 28px rgba(16,34,63,0.04);
}
.article-card h2 {
  margin-top: 28px;
  font-size: 30px;
  line-height: 1.15;
  letter-spacing: -0.03em;
}
.article-card h2:first-child { margin-top: 0; }
.article-card h3 {
  margin-top: 24px;
  font-size: 21px;
}
.topic-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin: 18px 0;
}
.topic {
  background: var(--soft);
  border: 1px solid #d8e5ff;
  padding: 12px 14px;
  border-radius: 14px;
  font-weight: 700;
}
.example {
  background: #0f1f39;
  color: white;
  border-radius: 20px;
  padding: 24px;
  margin: 22px 0;
}
.example strong { color: #dce7ff; }
.example .solution {
  margin-top: 14px;
  border-top: 1px solid rgba(255,255,255,0.18);
  padding-top: 14px;
}
.cta-box {
  background: linear-gradient(135deg, var(--brand2), var(--brand));
  color: white;
  border-radius: 22px;
  padding: 28px;
  margin: 32px 0;
}
.cta-box p { color: #e9efff; }
.cta-box .btn { background: white; color: var(--brand2); box-shadow: none; }
.related-list { columns: 2; padding-left: 18px; }
.side-card {
  position: sticky;
  top: 90px;
}
.side-card h2 { margin-top: 0; font-size: 20px; }
.side-card ul { padding-left: 18px; }
.faq details {
  border-top: 1px solid var(--line);
  padding: 16px 0;
}
.faq summary { cursor: pointer; font-weight: 800; }
.footer {
  border-top: 1px solid var(--line);
  padding: 32px 0;
  background: white;
  color: var(--muted);
  font-size: 14px;
}
.breadcrumb { font-size: 14px; color: var(--muted); margin-bottom: 12px; }
@media (max-width: 860px) {
  .main { grid-template-columns: 1fr; }
  .side-card { position: static; }
  .topic-grid { grid-template-columns: 1fr; }
  .related-list { columns: 1; }
  .nav { align-items: flex-start; flex-direction: column; padding: 16px 0; }
}