:root {
  color-scheme: light;
  --blue: #2563eb;
  --blue-dark: #1d4ed8;
  --blue-soft: #eff6ff;
  --ink: #172033;
  --muted: #5f6b7a;
  --line: #dbe3ec;
  --paper: #ffffff;
  --canvas: #f8fafc;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; overflow-y: scroll; }
body { margin: 0; background: var(--canvas); color: var(--ink); line-height: 1.65; }
a { color: var(--blue-dark); }
.site-header { position: sticky; top: 0; z-index: 40; background: rgba(255,255,255,.9); border-bottom: 1px solid rgba(226,232,240,.8); backdrop-filter: blur(16px); }
.nav { width: 100%; max-width: 1280px; height: 64px; margin: 0 auto; padding: 0 16px; display: flex; align-items: center; justify-content: space-between; gap: 16px; }
.brand { display: flex; align-items: center; gap: 10px; color: #0f172a; font-size: 1.25rem; line-height: 1.75rem; font-weight: 800; letter-spacing: -.025em; text-decoration: none; }
.brand-mark { width: 36px; height: 36px; display: grid; place-items: center; border-radius: 12px; background: #2563eb; color: #fff; box-shadow: 0 4px 10px rgba(37,99,235,.25); }
.nav-links { display: flex; align-items: center; gap: 8px; font-size: .875rem; }
.nav-links a { color: var(--muted); text-decoration: none; }
.nav-links a:hover { color: #3b82f6; }
.nav-detail, .nav-guide, .login-link { padding: 8px 12px; font-weight: 500; }
.login-link { color: #0f172a !important; }
.signup-button { height: 40px; padding: 0 20px; display: inline-flex; align-items: center; justify-content: center; border-radius: 12px; background: #2563eb; color: #fff !important; font-weight: 700; box-shadow: 0 8px 18px rgba(37,99,235,.2); }
.signup-button:hover { background: #1d4ed8; }
.button { display: inline-block; padding: 11px 18px; border-radius: 10px; background: var(--blue); color: white; font-weight: 700; text-decoration: none; }
.button:hover { background: var(--blue-dark); }
.hero { background: linear-gradient(135deg, #eff6ff 0%, #ffffff 54%, #f0fdfa 100%); border-bottom: 1px solid var(--line); }
.hero-inner { max-width: 900px; margin: 0 auto; padding: 72px 20px 64px; }
.eyebrow { color: var(--blue-dark); font-size: .85rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
h1 { max-width: 820px; margin: 10px 0 18px; font-size: clamp(2.15rem, 6vw, 4rem); line-height: 1.08; letter-spacing: -.035em; }
.lead { max-width: 760px; margin: 0; color: var(--muted); font-size: clamp(1.05rem, 2.5vw, 1.3rem); }
.layout { max-width: 900px; margin: 0 auto; padding: 48px 20px 72px; }
.article { background: var(--paper); border: 1px solid var(--line); border-radius: 18px; padding: clamp(24px, 5vw, 54px); box-shadow: 0 18px 45px rgba(24, 39, 75, .06); }
.article h2 { margin: 38px 0 10px; font-size: clamp(1.45rem, 3vw, 2rem); line-height: 1.25; }
.article h3 { margin: 26px 0 8px; line-height: 1.3; }
.article p, .article li { color: #334155; }
.article ul, .article ol { padding-left: 1.35rem; }
.article li + li { margin-top: 8px; }
.note { margin: 28px 0; padding: 18px 20px; border-left: 4px solid var(--blue); border-radius: 8px; background: var(--blue-soft); }
.checklist { list-style: none; padding: 0 !important; }
.checklist li { position: relative; padding-left: 30px; }
.checklist li::before { content: "✓"; position: absolute; left: 0; top: 0; color: var(--blue); font-weight: 900; }
.cta { margin-top: 42px; padding: 28px; border-radius: 16px; background: #172033; color: white; }
.cta h2 { margin-top: 0; color: white; }
.cta p { color: #dbeafe; }
.cards { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 18px; }
.card { display: flex; flex-direction: column; padding: 22px; border: 1px solid var(--line); border-radius: 16px; background: white; text-decoration: none; box-shadow: 0 8px 24px rgba(15, 23, 42, .04); transition: transform .2s ease, box-shadow .2s ease, border-color .2s ease; }
.card:hover { transform: translateY(-4px); border-color: #bfdbfe; box-shadow: 0 18px 38px rgba(15, 23, 42, .12); }
.card:focus-visible { outline: 3px solid rgba(37, 99, 235, .3); outline-offset: 3px; }
.card span { color: var(--blue-dark); font-weight: 800; }
.card h2 { margin: 8px 0; color: var(--ink); font-size: 1.25rem; }
.card p { margin: 0; color: var(--muted); }
.breadcrumbs { margin-bottom: 18px; color: var(--muted); font-size: .9rem; }
.breadcrumbs a { text-decoration: none; }
.site-footer { padding: 40px 0; border-top: 1px solid var(--line); background: white; color: var(--muted); }
.footer-inner { width: 100%; max-width: 1280px; margin: 0 auto; padding: 0 16px; display: flex; align-items: center; justify-content: space-between; gap: 24px; font-size: .875rem; }
.footer-brand { display: inline-flex; align-items: center; gap: 8px; color: #0f172a !important; font-weight: 800; text-decoration: none; }
.footer-logo-icon { width: 20px; height: 20px; fill: none; stroke: #2563eb; stroke-width: 2; stroke-linecap: round; stroke-linejoin: round; }
.footer-tagline { margin: 8px 0 0; color: #64748b; }
.footer-links { display: flex; gap: 24px; }
.footer-inner a { color: var(--muted); text-decoration: none; }
.footer-inner a:hover { color: #3b82f6; text-decoration: none; }
.footer-copyright { width: 100%; max-width: 1280px; margin: 28px auto 0; padding: 0 16px; color: #94a3b8; font-size: .75rem; }
@media (min-width: 640px) { .nav, .footer-inner, .footer-copyright { padding-left: 24px; padding-right: 24px; } }
@media (min-width: 1024px) { .nav, .footer-inner, .footer-copyright { padding-left: 32px; padding-right: 32px; } }
@media (max-width: 1023px) { .nav-guide { display: none; } }
@media (max-width: 767px) { .nav-detail { display: none; } }
@media (max-width: 639px) {
  .signup-button { display: none; }
}
@media (max-width: 720px) {
  .hero-inner { padding-top: 50px; }
  .cards { grid-template-columns: 1fr; }
  .article { border-radius: 14px; }
}
@media (max-width: 767px) {
  .footer-inner { flex-direction: column; align-items: flex-start; }
  .footer-links { flex-wrap: wrap; }
  .footer-copyright { margin-top: 28px; }
}