*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
:root{
  --bg:#f7f9fc;--surface:#fff;--surface-2:#f9fafb;--surface-3:#eff6ff;
  --border:#e5e7eb;--text:#111827;--muted:#4b5563;--dim:#6b7280;--soft:#9ca3af;
  --accent:#2563eb;--accent-dark:#1d4ed8;--accent-soft:#e0ecff;
  --success:#16a34a;--success-soft:#dcfce7;
  --warning:#d97706;--warning-soft:#fef3c7;
  --danger:#dc2626;--danger-soft:#fee2e2;
  --purple:#7c3aed;--purple-soft:#ede9fe;
  --teal:#0f766e;--teal-soft:#ccfbf1;
  --radius:18px;--shadow:0 10px 30px rgba(15,23,42,.04);
  --sans:Inter,Arial,sans-serif
}
html{scroll-behavior:smooth;overflow-x:hidden}
body{background:var(--bg);color:var(--text);font-family:var(--sans);font-size:15px;line-height:1.7;-webkit-font-smoothing:antialiased;overflow-x:hidden}
a{color:var(--accent);text-decoration:none}a:hover{text-decoration:underline}
img,table,pre,iframe,video,canvas{max-width:100%}
.hero,.article-hero,.hero-card,.content-card,.definition-card,.content-stack,.layout,.article-card,.sidebar,.sidebar-card,.related-card,.cta-block,.hub-cta,.calculator-callout,.formula-box,.table-wrap{max-width:100%;min-width:0}
.site-header{background:rgba(255,255,255,.92);border-bottom:1px solid var(--border);position:sticky;top:0;z-index:50;backdrop-filter:blur(10px)}
.nav-wrap{max-width:1120px;margin:0 auto;padding:14px 20px;display:flex;align-items:center;justify-content:space-between;gap:18px}
.brand{display:flex;align-items:center;gap:10px;color:var(--text);font-weight:800;font-size:18px;text-decoration:none}.brand:hover{text-decoration:none;color:var(--text)}
.brand-mark{width:32px;height:32px;border-radius:10px;background:var(--accent);color:#fff;display:grid;place-items:center;font-weight:800}
.top-nav{display:flex;align-items:center;gap:18px;font-size:14px;font-weight:600}.top-nav a{color:var(--muted)}.top-nav a:hover{color:var(--accent);text-decoration:none}
.menu-btn{display:none;background:none;border:none;cursor:pointer;padding:8px;color:var(--text);border-radius:8px;line-height:1}
.mobile-nav{visibility:hidden;pointer-events:none;position:fixed;top:0;left:0;right:0;bottom:0;z-index:9999}.mobile-nav.open{visibility:visible;pointer-events:auto}.mobile-nav-overlay{position:absolute;top:0;left:0;right:0;bottom:0;background:rgba(15,23,42,.5)}
.mobile-nav-panel{position:absolute;top:0;right:0;width:280px;max-width:85vw;height:100%;background:#fff;box-shadow:-4px 0 24px rgba(15,23,42,.15);display:flex;flex-direction:column;overflow-y:auto;transform:translateX(100%);transition:transform .25s ease}.mobile-nav.open .mobile-nav-panel{transform:translateX(0)}
.mobile-nav-head{display:flex;align-items:center;justify-content:space-between;padding:18px 20px;border-bottom:1px solid var(--border);background:#fff}.mobile-nav-head strong{font-weight:800;font-size:16px;color:var(--text)}
.mobile-nav-close{background:none;border:none;cursor:pointer;color:var(--dim);padding:6px;border-radius:8px;line-height:1;font-size:22px}.mobile-nav-links{flex:1}.mobile-nav-links a{display:block;padding:15px 20px;font-size:15px;font-weight:600;color:var(--text);border-bottom:1px solid var(--border);text-decoration:none}.mobile-nav-links a:active{background:var(--surface-2)}.mobile-nav-footer{padding:16px 20px;border-top:1px solid var(--border);font-size:12px;color:var(--dim)}
.main{max-width:1120px;margin:0 auto;padding:20px 20px 70px}.breadcrumb{font-size:13px;color:var(--dim);display:flex;flex-wrap:wrap;gap:8px;align-items:center;margin:0 0 14px}.breadcrumb a{color:var(--muted);font-weight:600}.breadcrumb span:last-child{color:var(--dim)}
.hero{background:linear-gradient(135deg,#fff,#f8fbff);border:1px solid var(--border);border-radius:var(--radius);box-shadow:var(--shadow);padding:22px 28px;margin-bottom:20px;position:relative}
.eyebrow{display:inline-flex;align-items:center;gap:6px;padding:5px 10px;border-radius:999px;background:var(--accent-soft);color:var(--accent-dark);font-size:12px;font-weight:800;letter-spacing:.04em;text-transform:uppercase;margin-bottom:10px}
h1{font-size:clamp(24px,3.4vw,38px);line-height:1.12;letter-spacing:-.04em;max-width:100%;margin-bottom:10px;color:var(--text)}.hero-subtitle{font-size:15px;line-height:1.6;max-width:100%;color:var(--muted)}
.meta-row{display:flex;flex-wrap:wrap;gap:8px;margin-top:14px}.meta-pill{display:inline-flex;align-items:center;gap:6px;padding:6px 10px;border-radius:999px;background:#fff;border:1px solid var(--border);font-size:12px;font-weight:700;color:var(--muted)}
.hero-search-panel{margin-top:14px;max-width:480px;position:relative;z-index:100}.hero-search-label{font-size:11.5px;font-weight:700;color:var(--muted);letter-spacing:.04em;text-transform:uppercase;margin-bottom:8px;display:block}.search-container{position:relative}.search-input-wrap{position:relative}.search-input{width:100%;padding:11px 14px 11px 40px;border-radius:12px;border:1px solid var(--border);background:var(--surface-2);color:var(--text);font-size:14px;font-family:var(--sans);outline:none;transition:border-color .15s ease,background .15s ease}.search-input:focus{border-color:var(--accent);background:#fff}.search-input::placeholder{color:var(--soft)}.search-icon{position:absolute;left:12px;top:50%;transform:translateY(-50%);color:var(--soft);pointer-events:none}.search-dropdown{position:absolute;left:0;right:0;top:calc(100% + 6px);background:var(--surface);border:1px solid var(--border);border-radius:14px;box-shadow:0 20px 40px rgba(15,23,42,.18);max-height:300px;overflow-y:auto;z-index:9999}.search-dropdown.hidden{display:none}.search-results{padding:4px 0}.search-result{display:flex;align-items:center;justify-content:space-between;gap:10px;padding:10px 14px;font-size:13.5px;color:var(--text);font-weight:600;border-bottom:1px solid var(--border);transition:background .1s ease;text-decoration:none;line-height:1.4}.search-result:last-child{border-bottom:0}.search-result:hover{background:var(--surface-2);text-decoration:none;color:var(--text)}.search-cat{font-size:11px;font-weight:700;color:var(--dim);background:var(--surface-2);padding:2px 7px;border-radius:999px;white-space:nowrap;flex-shrink:0}.search-empty{padding:12px 14px;font-size:13.5px;color:var(--dim)}
.layout{display:grid;grid-template-columns:minmax(0,1fr) 300px;gap:24px;align-items:start}.content-stack{display:flex;flex-direction:column;gap:18px}.content-card,.definition-card,.sidebar-card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);box-shadow:var(--shadow);padding:22px;min-width:0;max-width:100%;overflow-wrap:break-word;word-wrap:break-word}.definition-card{border-left:4px solid var(--accent)}
h2{font-size:21px;line-height:1.25;margin-bottom:10px;letter-spacing:-.025em}h3{font-size:17px;line-height:1.35;margin:16px 0 8px}.content-card p,.definition-card p{color:var(--muted);margin-bottom:12px}.content-card p:last-child,.definition-card p:last-child{margin-bottom:0}.content-card ul{padding-left:20px;color:var(--muted);margin:8px 0 0}.content-card li{margin:6px 0}.lead-definition{font-size:17px;color:var(--text)!important;font-weight:600}.formula-box{background:#0f172a;color:#e5e7eb;border-radius:14px;padding:14px 16px;overflow-x:auto;max-width:100%;margin-top:10px}.formula-box code{display:block;max-width:100%;white-space:pre;font-family:ui-monospace,SFMono-Regular,Menlo,Monaco,Consolas,"Liberation Mono",monospace;font-size:13px;line-height:1.6}.example-box{background:var(--surface-3);border:1px solid #bfdbfe;border-radius:14px;padding:14px;margin-top:10px}.example-box strong{color:var(--accent-dark)}
.callout{border-radius:14px;padding:14px 16px;background:var(--warning-soft);border:1px solid #fde68a;color:#78350f;margin-top:10px}.callout p{color:#78350f;margin:0}.calculator-callout{display:flex;align-items:center;justify-content:space-between;gap:16px;background:var(--accent);color:#fff;border-radius:16px;padding:18px;overflow:hidden}.calculator-callout p{color:#dbeafe;margin:4px 0 0}.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;border-radius:999px;padding:10px 16px;border:1px solid transparent;font-size:14px;font-weight:800;text-decoration:none;cursor:pointer}.btn:hover{text-decoration:none}.btn-white{background:#fff;color:var(--accent-dark)}.btn-primary{background:var(--accent);color:#fff}.btn-primary:hover{background:var(--accent-dark);color:#fff}
.term-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;margin-top:10px}.term-pill{display:block;padding:12px;border-radius:14px;border:1px solid var(--border);background:var(--surface-2);font-weight:700;color:var(--text)}.term-pill:hover{color:var(--accent);text-decoration:none;background:#fff}.sidebar{position:sticky;top:86px;display:flex;flex-direction:column;gap:16px}.sidebar-card{padding:16px}.sidebar-card h2{font-size:14px;text-transform:uppercase;letter-spacing:.06em;color:var(--dim);margin-bottom:10px}.toc{display:flex;flex-direction:column;gap:0}.toc a{display:block;padding:9px 0;border-bottom:1px solid var(--border);font-size:14px;font-weight:600;color:var(--text)}.toc a:last-child{border-bottom:0}.toc a:hover{color:var(--accent);text-decoration:none}.toc-select{display:none;width:100%;padding:10px 12px;border:1px solid var(--border);border-radius:12px;background:#fff;color:var(--text);font-size:14px;font-weight:600;cursor:pointer}
.related-guide-nav,.also-useful-nav,.quick-links-nav{display:flex;flex-direction:column;gap:0}.related-guide-nav a,.also-useful-nav a,.quick-links-nav a{display:block;padding:10px 0;font-size:14px;font-weight:600;color:var(--text);border-bottom:1px solid var(--border);text-decoration:none;line-height:1.4}.related-guide-nav a:last-child,.also-useful-nav a:last-child,.quick-links-nav a:last-child{border-bottom:0}.related-guide-nav a:hover,.also-useful-nav a:hover,.quick-links-nav a:hover{color:var(--accent);text-decoration:none}.related-sidebar-mobile,.also-useful-sidebar-mobile,.quick-links-sidebar-mobile{display:none;padding:0 12px 24px;box-sizing:border-box;width:100%}
.footer{border-top:1px solid var(--border);background:#fff;padding:40px 20px 24px;margin-top:40px}.footer-inner{max-width:1120px;margin:0 auto}.footer-cols{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:32px;margin-bottom:32px}.footer-col h4{font-size:11px;font-weight:800;letter-spacing:.08em;text-transform:uppercase;color:var(--dim);margin-bottom:12px}.footer-col ul{list-style:none;display:flex;flex-direction:column;gap:8px}.footer-col ul li a{color:var(--muted);font-size:13px;font-weight:600;transition:color .12s ease}.footer-col ul li a:hover{color:var(--accent);text-decoration:none}.footer-base{border-top:1px solid var(--border);padding-top:20px;color:var(--dim);font-size:12px}
@media(max-width:980px){.layout{display:flex;flex-direction:column}.sidebar{position:static;order:-1;width:100%}.toc{display:none}.toc-select{display:block}.related-sidebar{display:none}.also-useful-sidebar{display:none}.quick-links-sidebar{display:none}.related-sidebar-mobile{display:block}.also-useful-sidebar-mobile{display:block}.quick-links-sidebar-mobile{display:block}.term-grid{grid-template-columns:1fr}}
@media(max-width:760px){.top-nav{display:none}.menu-btn{display:block}.main{padding:16px 12px 48px}.hero{padding:16px}.content-card,.definition-card{padding:16px}.sidebar-card{padding:14px}.calculator-callout{padding:16px;display:block}.calculator-callout .btn{margin-top:12px;display:block;text-align:center}.btn{width:100%;box-sizing:border-box}h1{font-size:22px}h2{font-size:19px;margin-bottom:10px}h3{font-size:16px}.hero-subtitle{font-size:14px}.hero-search-panel{max-width:100%}.footer-cols{grid-template-columns:repeat(2,minmax(0,1fr));gap:20px}}
@media(max-width:420px){.footer-cols{grid-template-columns:1fr}}