:root{--ink: #17202a;--muted: #5b6675;--line: #d8e0ea;--paper: #fbfcff;--white: #fff;--blue: #1c64f2;--green: #047857;--amber: #b45309;--rose: #be123c;--indigo: #4f46e5;--sky: #0284c7;--shadow: 0 18px 55px rgba(23, 32, 42, .12)}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,sans-serif;color:var(--ink);background:var(--paper);line-height:1.65}a{color:inherit}a:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible,textarea:focus-visible{outline:3px solid #93c5fd;outline-offset:3px}img,canvas{max-width:100%}.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}.skip-link{position:absolute;left:-999px;top:12px;background:var(--ink);color:#fff;padding:10px 14px;z-index:50}.skip-link:focus{left:12px}.site-header{position:sticky;top:0;z-index:20;background:#ffffffeb;backdrop-filter:blur(14px);border-bottom:1px solid var(--line)}.nav-shell{max-width:1180px;margin:0 auto;display:flex;align-items:center;justify-content:space-between;padding:12px 20px}.brand{display:flex;gap:10px;align-items:center;min-height:44px;text-decoration:none}.brand-mark{display:grid;place-items:center;width:42px;height:42px;border-radius:8px;background:var(--ink);color:#fff;font-weight:800}.brand-logo{display:block;width:208px;height:auto}.brand small{display:block;color:var(--muted);font-size:12px}.nav-links{display:flex;gap:4px;align-items:center}.nav-links a{display:inline-flex;align-items:center;min-height:44px;padding:9px 12px;text-decoration:none;border-radius:8px;color:#334155;font-weight:650}.nav-links a:hover,.nav-links a:focus{background:#eef4ff;color:#0f3d8f}.nav-toggle{display:none}.hero{position:relative;min-height:720px;display:flex;align-items:center;overflow:hidden;background:#eef6ff}.hero canvas{position:absolute;inset:0;width:100%;height:100%;opacity:.85}.hero-inner{position:relative;max-width:1180px;margin:0 auto;padding:92px 20px 70px}.eyebrow{margin:0 0 12px;text-transform:uppercase;letter-spacing:.08em;font-size:12px;font-weight:800;color:#0f766e}.hero h1,.page-hero h1{max-width:900px;margin:0;font-size:76px;line-height:1.02;letter-spacing:0;overflow-wrap:anywhere}.hero-copy,.page-hero p{max-width:760px;font-size:19px;color:#334155}.hero-actions{display:flex;gap:12px;flex-wrap:wrap;margin:28px 0}.button{display:inline-flex;align-items:center;justify-content:center;min-height:46px;padding:11px 17px;border-radius:8px;text-decoration:none;font-weight:800}.button.primary{background:var(--blue);color:#fff}.button.secondary{background:#fff;color:#17324d;border:1px solid var(--line)}.stat-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:12px;margin-top:34px;max-width:920px}.stat-card{background:#ffffffe0;border:1px solid rgba(216,224,234,.9);border-radius:8px;padding:16px;box-shadow:0 10px 35px #17202a14}.stat-card strong{display:block;font-size:30px;line-height:1}.stat-card span{color:var(--muted);font-size:13px}.band,.split-band{max-width:1180px;margin:0 auto;padding:72px 20px}.split-band{display:grid;grid-template-columns:minmax(0,1.35fr) minmax(280px,.65fr);gap:42px;align-items:start}.section-head{max-width:780px;margin-bottom:28px}.section-head h2,.split-band h2{font-size:44px;line-height:1.08;margin:0 0 12px;overflow-wrap:anywhere}.section-head p,.split-band p{color:var(--muted)}.level-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:16px}.level-card,.chapter-card,.method-panel{background:var(--white);border:1px solid var(--line);border-radius:8px;box-shadow:0 12px 42px #17202a12}.level-card{padding:20px;min-height:240px;display:flex;flex-direction:column}.card-topline{font-size:12px;font-weight:800;text-transform:uppercase;color:#64748b}.level-card h3,.chapter-card h3{font-size:22px;line-height:1.18;margin:14px 0 10px}.level-card h3 a,.chapter-card h3 a{display:inline-flex;align-items:center;min-height:44px;text-decoration:none}.level-card p,.chapter-card p{color:var(--muted);margin:0}.mini-metrics{display:flex;flex-wrap:wrap;gap:7px;margin-top:auto;padding-top:20px}.mini-metrics span,.pill-link,.resource-type{border:1px solid var(--line);border-radius:999px;padding:5px 9px;font-size:12px;font-weight:750;background:#f8fafc}.tone-emerald{border-top:4px solid var(--green)}.tone-sky{border-top:4px solid var(--sky)}.tone-indigo{border-top:4px solid var(--indigo)}.tone-amber{border-top:4px solid var(--amber)}.tone-rose{border-top:4px solid var(--rose)}.tone-teal{border-top:4px solid #0f766e}.tone-violet{border-top:4px solid #7c3aed}.tone-orange{border-top:4px solid #ea580c}.method-panel{padding:22px}.method-panel h3{margin-top:0;font-size:22px}.check-list{padding:0;margin:18px 0 0;list-style:none}.check-list li{position:relative;padding-left:28px;margin:10px 0}.check-list li:before{content:"";position:absolute;left:0;top:.62em;width:14px;height:8px;border-left:3px solid var(--green);border-bottom:3px solid var(--green);transform:rotate(-45deg)}.page-hero{max-width:1180px;margin:0 auto;padding:86px 20px 34px}.page-hero.compact h1{font-size:60px}.chapter-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}.chapter-card{padding:20px}.chapter-number{font-weight:900;color:#94a3b8}.pill-row{display:flex;flex-wrap:wrap;gap:10px}.pill-link{display:inline-flex;align-items:center;min-height:44px;text-decoration:none;background:#fff}.resource-list{display:grid;gap:10px}.resource-row{display:grid;grid-template-columns:150px minmax(0,1fr) 170px;gap:12px;align-items:center;min-height:54px;padding:13px 14px;background:#fff;border:1px solid var(--line);border-radius:8px;text-decoration:none}.resource-row:hover,.resource-row:focus{border-color:#93c5fd;box-shadow:0 10px 30px #1c64f21a}.method-panel .resource-row{grid-template-columns:1fr}.resource-main{display:grid;gap:3px;min-width:0}.resource-main small{color:var(--muted);overflow:hidden;text-overflow:ellipsis;white-space:nowrap}.resource-meta{display:flex;justify-content:flex-end;gap:6px;flex-wrap:wrap}.resource-meta span{border:1px solid var(--line);border-radius:999px;padding:4px 8px;font-size:12px;color:#475569;background:#f8fafc}.course-blocks{display:grid;gap:14px;margin-top:22px}.course-block{background:#fff;border:1px solid var(--line);border-radius:8px;padding:18px}.course-block h3,.example-box h3{margin-top:0}.course-block p,.example-box p{margin-bottom:0}.example-box+.example-box{margin-top:16px}.followup-panel{margin-top:28px}.course-visual{margin:0 0 22px}.course-visual svg{display:block;width:100%;border-radius:8px;border:1px solid var(--line)}.course-visual text{font:800 18px Inter,ui-sans-serif,system-ui,sans-serif;fill:var(--ink)}.course-visual figcaption{margin-top:8px;font-size:13px;color:var(--muted)}.study-steps{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:10px;margin:22px 0}.study-steps div{display:grid;gap:6px;align-content:start;min-height:92px;padding:14px;border:1px solid var(--line);border-radius:8px;background:#fff}.study-steps strong{display:grid;place-items:center;width:30px;height:30px;border-radius:999px;background:var(--ink);color:#fff}.study-steps span{font-weight:750}.formula-panel{margin-top:22px;padding:18px;border:1px solid var(--line);border-radius:8px;background:#f8fafc}.formula-panel h3,.quick-check h3{margin-top:0}.formula-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:10px}.formula-grid code{display:block;padding:12px;border:1px solid #dbeafe;border-radius:8px;background:#fff;white-space:normal;overflow-wrap:anywhere}.quick-check{margin-top:22px;padding-top:18px;border-top:1px solid var(--line)}.related-resources{margin-top:28px}.chapter-nav{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px;margin-top:30px}.chapter-nav-link{display:grid;gap:4px;min-height:72px;padding:16px;border:1px solid var(--line);border-radius:8px;background:#fff;text-decoration:none}.chapter-nav-link span{color:var(--muted);font-size:13px;font-weight:750}.chapter-nav-link.next{text-align:right}.empty-actions{display:flex;flex-wrap:wrap;gap:10px;margin-top:14px}.muted{color:var(--muted)}.archive-toolbar{display:grid;grid-template-columns:2fr repeat(4,minmax(130px,1fr));gap:12px;margin-bottom:22px}.archive-toolbar label{display:grid;gap:6px;font-weight:800}.archive-toolbar input,.archive-toolbar select{width:100%;min-height:46px;border:1px solid var(--line);border-radius:8px;padding:10px 12px;font:inherit;background:#fff}.archive-results{display:grid;gap:10px}.archive-summary{margin:0 0 14px;color:var(--muted);font-weight:750}.prose{max-width:840px}.prose p{color:var(--muted)}.site-footer{border-top:1px solid var(--line);background:#101820;color:#fff;margin-top:50px}.footer-grid{max-width:1180px;margin:0 auto;padding:36px 20px;display:grid;grid-template-columns:2fr 1fr 1fr;gap:22px}.footer-grid p{color:#cbd5e1}.footer-grid a{display:flex;align-items:center;min-height:44px;color:#e2e8f0;text-decoration:none}.footer-title{display:block;font-weight:900;margin-bottom:8px}@media(max-width:1050px){.level-grid{grid-template-columns:repeat(2,minmax(0,1fr))}}@media(max-width:900px){.nav-toggle{display:inline-flex;justify-content:center;width:46px;min-height:44px;align-items:center;border:1px solid var(--line);background:#fff;border-radius:8px;padding:8px 12px}.brand-logo{width:174px}.nav-toggle-icon,.nav-toggle-icon:before,.nav-toggle-icon:after{display:block;width:18px;height:2px;border-radius:999px;background:var(--ink)}.nav-toggle-icon{position:relative}.nav-toggle-icon:before,.nav-toggle-icon:after{content:"";position:absolute;left:0}.nav-toggle-icon:before{top:-6px}.nav-toggle-icon:after{top:6px}.nav-links{display:none;position:absolute;left:16px;right:16px;top:68px;background:#fff;border:1px solid var(--line);border-radius:8px;box-shadow:var(--shadow);padding:10px;flex-direction:column;align-items:stretch}.nav-links.is-open{display:flex}.hero{min-height:auto}.hero-inner{padding-top:70px}.stat-grid,.level-grid,.chapter-grid,.archive-toolbar,.footer-grid,.split-band,.resource-row{grid-template-columns:1fr}.resource-meta{justify-content:flex-start}.resource-main small{white-space:normal}.study-steps,.formula-grid,.chapter-nav{grid-template-columns:1fr}.resource-type{width:max-content}.hero h1,.page-hero h1{font-size:40px}.page-hero.compact h1{font-size:38px}.section-head h2,.split-band h2{font-size:32px}}@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}}