:root {
  --primary: #2563EB; --primary-dark: #1D4ED8; --primary-soft: #EFF6FF;
  --bg: #F8FAFC; --surface: #FFFFFF; --text: #0F172A; --text-2: #64748B; --border: #E2E8F0;
  --success: #16A34A; --radius: 16px;
  --shadow: 0 1px 2px rgba(15,23,42,.04), 0 8px 24px rgba(15,23,42,.06);
}
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body { font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; background: var(--bg); color: var(--text); line-height: 1.7; -webkit-font-smoothing: antialiased; overflow-x: hidden; }
a { color: var(--primary); }
a:hover { color: var(--primary-dark); }
a:focus-visible, summary:focus-visible { outline: 3px solid var(--primary); outline-offset: 3px; border-radius: 6px; }
.skip { position: absolute; left: -999px; top: .5rem; background: var(--primary); color: #fff; padding: .5rem 1rem; border-radius: 8px; z-index: 50; }
.skip:focus { left: .5rem; }
.wrap { max-width: 72rem; margin: 0 auto; padding: 0 1.25rem; }
.nav { background: var(--surface); border-bottom: 1px solid var(--border); }
.nav .wrap { display: flex; align-items: center; justify-content: space-between; height: 4rem; gap: 1rem; }
.brand { display: flex; align-items: center; gap: .6rem; font-weight: 700; color: var(--text); text-decoration: none; }
.brand svg { width: 32px; height: 32px; }
.nav-links { display: flex; gap: 1.5rem; font-size: .95rem; }
.nav-links a { color: var(--text-2); text-decoration: none; min-height: 44px; display: inline-flex; align-items: center; }
.nav-links a:hover { color: var(--primary); }
.crumb { font-size: .85rem; color: var(--text-2); padding: 1.5rem 0 0; }
.crumb a { color: var(--text-2); }
article.post { max-width: 46rem; margin: 0 auto; padding: 1rem 1.25rem 4rem; }
.eyebrow { display: inline-block; font-size: .8rem; font-weight: 600; letter-spacing: .04em; text-transform: uppercase; color: var(--primary); background: var(--primary-soft); padding: .3rem .75rem; border-radius: 999px; margin: 1rem 0; }
h1 { font-size: clamp(1.75rem, 5vw, 2.6rem); line-height: 1.2; letter-spacing: -.02em; }
.meta { color: var(--text-2); font-size: .9rem; margin: 1rem 0 2rem; }
.lead { font-size: 1.15rem; color: var(--text-2); margin-bottom: 2rem; }
.post h2 { font-size: clamp(1.35rem, 3.5vw, 1.75rem); line-height: 1.3; margin: 2.5rem 0 .75rem; letter-spacing: -.01em; }
.post h3 { font-size: 1.15rem; margin: 1.75rem 0 .5rem; }
.post p { margin-bottom: 1.1rem; }
.post ul, .post ol { margin: 0 0 1.25rem 1.25rem; }
.post li { margin-bottom: .5rem; }
.toc { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 1.25rem 1.5rem; margin-bottom: 2rem; }
.toc b { display: block; margin-bottom: .5rem; }
.toc ol { margin-bottom: 0; }
.note { background: var(--primary-soft); border: 1px solid #DBEAFE; border-radius: 12px; padding: 1rem 1.25rem; margin: 1.5rem 0; font-size: .95rem; }
.cta { background: var(--surface); border: 1px solid var(--border); border-radius: 20px; box-shadow: var(--shadow); padding: 1.75rem; margin: 3rem 0 1rem; }
.cta h2 { margin-top: 0; }
.btn { display: inline-flex; align-items: center; min-height: 48px; padding: 0 1.4rem; border-radius: 12px; background: var(--primary); color: #fff; font-weight: 600; text-decoration: none; margin-top: .5rem; }
.btn:hover { background: var(--primary-dark); color: #fff; }
.related { margin-top: 2.5rem; }
.related ul { list-style: none; margin: 0; display: grid; gap: .5rem; }
details { background: var(--surface); border: 1px solid var(--border); border-radius: 14px; margin-bottom: .75rem; }
summary { cursor: pointer; padding: 1rem 1.25rem; font-weight: 600; min-height: 48px; }
details p { padding: 0 1.25rem 1rem; margin: 0; color: var(--text-2); }
.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(16rem, 1fr)); gap: 1.25rem; margin: 2rem 0; }
.card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow); padding: 1.5rem; }
.card h2 { font-size: 1.15rem; margin: 0 0 .5rem; }
.card p { color: var(--text-2); font-size: .95rem; margin-bottom: .75rem; }
footer { border-top: 1px solid var(--border); background: var(--surface); padding: 2rem 0; color: var(--text-2); font-size: .9rem; }
footer .wrap { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 1rem; }
footer a { color: var(--text-2); }
@media (max-width: 640px) { .nav-links { gap: 1rem; font-size: .9rem; } .btn { width: 100%; justify-content: center; } }

.fig { margin: 0 0 2rem; }
.fig img, .thumb { display: block; width: 100%; height: auto; border-radius: var(--radius); }
.thumb { margin-bottom: 1rem; }