.lesson-hero{min-height:430px;padding:155px 0 78px;color:#fff;background:radial-gradient(circle at 82% 28%,#24446eaa 0,transparent 38%),linear-gradient(120deg,var(--navy),var(--navy2));position:relative;overflow:hidden}.lesson-hero:before{content:'';position:absolute;inset:0;opacity:.12;background-image:linear-gradient(#fff2 1px,transparent 1px),linear-gradient(90deg,#fff2 1px,transparent 1px);background-size:76px 76px}.lesson-hero .wrap{position:relative}.lesson-hero h1{margin:12px 0 18px;font-size:clamp(48px,7vw,82px);line-height:1;letter-spacing:-.045em;font-weight:400}.lesson-hero p{max-width:760px;margin:0;color:#c4ccda;font-size:18px;line-height:1.7}.lesson-shell{padding:72px 0 100px}.lesson-grid{display:grid;grid-template-columns:minmax(0,1fr) 270px;gap:38px;align-items:start}.lesson-content{display:grid;gap:28px}.lesson-card{background:#fff;border:1px solid #ddd9d1;border-top:5px solid var(--red);padding:clamp(24px,4vw,44px);box-shadow:0 18px 45px #0712240d}.lesson-card h2{margin:0 0 22px;font-size:clamp(30px,4vw,44px);font-weight:400;letter-spacing:-.025em}.lesson-card h3{margin:30px 0 14px;font-size:25px;font-weight:400}.lesson-card p,.lesson-card li{line-height:1.75}.math-list{display:grid;gap:12px;margin:0;padding:0;list-style:none}.math-row{padding:13px 16px;background:#f8f5ef;border-left:4px solid #163d70;overflow-x:auto}.formula-box{margin:22px 0;padding:20px;background:#071b3d;color:#fff;border-radius:4px;overflow-x:auto}.formula-box .mjx-container{color:#fff!important}.pascal{width:100%;border-collapse:collapse;text-align:center}.pascal td{padding:7px 5px}.pascal td:last-child{text-align:left;padding-left:20px;color:#4f5969}.pascal .arrow{color:var(--red);font-weight:800}.note{padding:18px 20px;border:1px solid #e2d8c7;background:#fff8e9}.toc{position:sticky;top:24px;background:#071b3d;color:#fff;padding:24px}.toc strong{display:block;margin-bottom:14px;font-family:Georgia,serif;font-size:23px;font-weight:400}.toc a{display:block;padding:11px 0;border-top:1px solid #ffffff24;color:#c8d0dc;font-size:14px}.toc a:hover{color:#fff}.page-nav{display:flex;justify-content:space-between;gap:14px;margin-top:14px}.page-nav a{padding:14px 18px;background:#163d70;color:#fff;font-weight:800}.page-nav a:last-child{background:var(--red)}@media(max-width:900px){.lesson-grid{grid-template-columns:1fr}.toc{position:static;order:-1}.pascal{font-size:14px}}@media(max-width:520px){.lesson-hero{padding-top:135px}.lesson-card{padding:22px 16px}.page-nav{flex-direction:column}.page-nav a{text-align:center}}