:root{--ink:#14202b;--muted:#586775;--paper:#f8fafc;--surface:#fff;--line:#d8e1e8;--brand:#075a9b;--brand-dark:#034574;--accent:#eaf5ff;--radius:16px;color-scheme:light dark}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--paper);color:var(--ink);font-family:ui-rounded,SF Pro Rounded,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,sans-serif;font-size:16px;line-height:1.6}.page-shell{width:min(100% - 32px,760px);margin:0 auto;padding:32px 0 52px}.site-header{background:color-mix(in srgb,var(--surface) 94%,transparent);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:10;backdrop-filter:blur(16px)}.header-inner{width:min(100% - 32px,960px);min-height:64px;margin:auto;display:flex;align-items:center;justify-content:space-between;gap:16px}.brand{font-weight:800;color:var(--ink);text-decoration:none;letter-spacing:-.02em}.brand span{color:var(--muted);font-weight:600}.site-header nav{display:flex;gap:4px}.site-header nav a{color:var(--ink);text-decoration:none;padding:10px 12px;border-radius:10px}.site-header nav a[aria-current=page],.site-header nav a:hover{background:var(--accent);color:var(--brand-dark)}.skip-link{position:absolute;left:12px;top:-100px;background:var(--ink);color:#fff;padding:8px 12px;border-radius:8px;z-index:100}.skip-link:focus{top:12px}.hero{padding:20px 0 36px}.eyebrow{margin:0 0 6px;color:var(--brand);font-size:.82rem;font-weight:800;letter-spacing:.08em;text-transform:uppercase}.hero h1,.topic-header h1,.search-page h1{font-size:clamp(2rem,7vw,3.4rem);line-height:1.08;letter-spacing:-.045em;margin:.1em 0 .38em}.hero>p:not(.eyebrow){max-width:600px;font-size:1.1rem;color:var(--muted);margin:0 0 24px}.search-form{display:flex;gap:8px;max-width:620px}.search-form input{min-width:0;flex:1;border:1px solid var(--line);background:var(--surface);color:var(--ink);border-radius:12px;padding:13px 14px;font:inherit}.search-form button,.button{min-height:48px;border:0;border-radius:12px;padding:10px 16px;font:inherit;font-weight:750;text-decoration:none;display:inline-flex;align-items:center;justify-content:center;gap:8px}.search-form button,.button-primary{background:var(--brand);color:#fff}.search-form button:hover,.button-primary:hover{background:var(--brand-dark)}.section-heading{display:flex;justify-content:space-between;gap:16px;align-items:end;margin:0 0 12px}.section-heading h2{margin:0;font-size:1.5rem;letter-spacing:-.03em}.section-heading>span{color:var(--muted);font-size:.9rem}.topic-grid{display:grid;gap:10px}.topic-card{display:grid;grid-template-columns:42px 1fr auto;gap:10px;align-items:center;min-height:68px;border:1px solid var(--line);border-radius:var(--radius);padding:12px 14px;background:var(--surface);text-decoration:none;color:var(--ink);transition:transform .15s ease,border-color .15s ease,box-shadow .15s ease}.topic-card:hover{transform:translateY(-1px);border-color:var(--brand);box-shadow:0 8px 20px #075a9b15}.topic-number{font-weight:800;color:var(--brand)}.topic-title{font-weight:700}.topic-arrow{font-size:1.3rem;color:var(--brand)}.reference-links{display:grid;grid-template-columns:1fr 1fr;gap:10px;margin:28px 0}.reference-links a{display:grid;gap:2px;text-decoration:none;color:var(--ink);background:var(--accent);border-radius:var(--radius);padding:16px}.reference-links span{font-size:.86rem;color:var(--muted)}.quizlet-cta{display:flex;justify-content:space-between;gap:20px;align-items:center;margin:32px 0;padding:20px;border-radius:var(--radius);background:#e7f4ed;border:1px solid #c2e7d0}.quizlet-cta h2{font-size:1.25rem;margin:0}.quizlet-cta p:not(.eyebrow){margin:.2rem 0 0;color:var(--muted);font-size:.94rem}.button-disabled{background:#c9d4da;color:#3f4e57;cursor:not-allowed;white-space:nowrap}.notice,.empty-study,.search-placeholder{border-left:4px solid var(--brand);background:var(--accent);padding:14px 16px;margin:0 0 28px}.topic-header{padding:0 0 24px}.back-link{font-size:.93rem;color:var(--brand-dark);font-weight:700}.topic-header-row{display:flex;justify-content:space-between;align-items:start;gap:16px;margin-top:17px}.language-switcher{border:1px solid var(--line);background:var(--surface);border-radius:11px;display:flex;overflow:hidden;flex:0 0 auto}.language-switcher a,.language-switcher span{padding:8px 10px;text-decoration:none;color:var(--ink);font-size:.88rem;font-weight:700}.language-switcher a[aria-current=page]{background:var(--brand);color:#fff}.language-switcher span{color:var(--muted)}.prose{font-family:ui-serif,Georgia,Cambria,Times New Roman,serif;font-size:1.08rem;line-height:1.75}.prose>:first-child{margin-top:0}.prose h1,.prose h2,.prose h3{font-family:ui-rounded,system-ui,sans-serif;line-height:1.2;letter-spacing:-.025em;scroll-margin-top:86px}.prose h1{display:none}.prose h2{margin-top:2.4em;font-size:1.55rem}.prose h3{margin-top:1.8em;font-size:1.22rem}.prose a{color:var(--brand-dark);font-weight:700}.prose table{display:block;max-width:100%;overflow:auto;border:1px solid var(--line);border-radius:10px;border-spacing:0;font-size:.92rem}.prose th,.prose td{padding:10px 12px;text-align:left;vertical-align:top;border-bottom:1px solid var(--line)}.prose th{background:var(--accent);font-family:ui-sans-serif,system-ui,sans-serif}.prose tr:last-child td{border-bottom:0}.prose details{margin:1.2em 0;padding:12px 14px;border-radius:10px;background:var(--accent);border:1px solid #c7dfef}.prose summary{cursor:pointer;font-family:ui-sans-serif,system-ui,sans-serif;font-weight:800}.prose blockquote{border-left:4px solid var(--brand);padding-left:16px;margin-left:0;color:var(--muted)}.topic-pager{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin-top:28px}.topic-pager a{min-height:74px;padding:12px;border:1px solid var(--line);border-radius:12px;color:var(--ink);text-decoration:none;font-weight:700}.topic-pager a:last-child{text-align:right}.topic-pager span{display:block;color:var(--brand);font-size:.8rem;margin-bottom:4px}.reading-progress{height:3px;background:transparent;position:fixed;top:64px;left:0;right:0;z-index:12}.reading-progress span{display:block;height:100%;width:0;background:#35a6e8}.site-footer{border-top:1px solid var(--line);padding:24px 16px;text-align:center;color:var(--muted);font-size:.83rem}.search-page{padding-top:20px}.search-placeholder{margin-top:24px}.muted{color:var(--muted)}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}a:focus-visible,button:focus-visible,input:focus-visible,summary:focus-visible{outline:3px solid #e08a00;outline-offset:3px}@media(max-width:480px){.page-shell{width:min(100% - 24px,760px);padding-top:24px}.header-inner{width:min(100% - 24px,960px)}.brand span{display:none}.search-form{flex-direction:column}.search-form button{width:100%}.reference-links{grid-template-columns:1fr}.quizlet-cta{align-items:stretch;flex-direction:column}.topic-header-row{flex-direction:column}.topic-pager{grid-template-columns:1fr}.topic-pager a:last-child{text-align:left}.prose{font-size:1.03rem}}@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important;transition:none!important}}@media(prefers-color-scheme:dark){:root{--ink:#edf4f8;--muted:#b2c0ca;--paper:#0e1820;--surface:#162530;--line:#2c3d49;--brand:#65bbf4;--brand-dark:#a1d8fa;--accent:#163343}.quizlet-cta{background:#123a2b;border-color:#246344}.button-primary,.search-form button{color:#06131d;background:#65bbf4}.button-primary:hover,.search-form button:hover{background:#a1d8fa}.button-disabled{background:#40515c;color:#dae4e9}}