:root{
  --ink:#22204f;
  --paper:#fffdf9;
  --paper-2:#f6f3ff;
  --yellow:#ffd84d;
  --yellow-dark:#e6b900;
  --purple:#5b3fc4;
  --blue:#3b82f6;
  --aqua:#7de3d4;
  --coral:#ff8a73;
  --line:#ded9ef;
  --muted:#68647f;
  --white:#ffffff;
  --max:1180px;
  --article:760px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--paper);color:var(--ink);font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;line-height:1.55}
a{color:inherit;text-decoration:none}
img{display:block;max-width:100%;height:auto}
.shell{width:min(calc(100% - 40px),var(--max));margin:0 auto}
.site-header{position:sticky;top:0;z-index:30;background:rgba(255,253,249,.94);backdrop-filter:blur(14px);border-bottom:1px solid rgba(34,32,79,.08)}
.nav-inner{display:flex;align-items:center;justify-content:space-between;min-height:76px}
.text-logo,.footer-logo{font-weight:900;letter-spacing:-.045em;color:var(--purple)}
.text-logo{font-size:24px;position:relative}
.text-logo:after{content:'+';display:inline-grid;place-items:center;width:18px;height:18px;margin-left:4px;border-radius:50%;background:var(--yellow);color:var(--ink);font-size:13px;vertical-align:top}
.nav-links{display:flex;align-items:center;gap:26px;font-size:15px}
.nav-cta,.btn{display:inline-flex;align-items:center;justify-content:center;background:var(--purple);color:#fff;border:2px solid var(--purple);border-radius:999px;padding:13px 22px;font-weight:800;box-shadow:0 5px 0 #392688;transition:.18s ease}
.nav-cta:hover,.btn:hover{background:var(--yellow);border-color:var(--ink);color:var(--ink);box-shadow:0 3px 0 var(--ink);transform:translateY(2px)}
.hero{padding:72px 0 80px;background:linear-gradient(135deg,#fffdf9 0%,#f5f1ff 55%,#e9fbf7 100%);overflow:hidden}
.hero-grid{display:grid;grid-template-columns:minmax(0,1fr) minmax(360px,.86fr);gap:72px;align-items:center}
.hero h1{font-size:clamp(58px,7vw,94px);line-height:.92;letter-spacing:-.07em;margin:0 0 28px;max-width:720px}
.hero h1 em{font-style:normal;color:var(--purple);position:relative;white-space:nowrap}
.hero h1 em:after{content:'';position:absolute;left:0;right:0;bottom:-8px;height:11px;background:var(--yellow);border-radius:50%;transform:rotate(-2deg);z-index:-1}
.hero p{font-size:21px;max-width:700px;color:#403c34;margin:0 0 30px}
.hero-meta{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:24px}
.hero-meta span{font-size:13px;font-weight:800;background:#fff;border:1px solid var(--line);border-radius:999px;padding:7px 11px}
.hero-visual{position:relative;padding:26px 22px 38px 38px}
.hero-image{aspect-ratio:4/5;object-fit:cover;width:100%;border-radius:48% 48% 28px 28px;box-shadow:18px 18px 0 var(--yellow)}
.hero-note{position:absolute;left:0;bottom:8px;background:#fff;border:2px solid var(--ink);border-radius:18px;padding:14px 18px;box-shadow:6px 6px 0 var(--aqua)}
.hero-note strong,.hero-note span{display:block}.hero-note span{font-size:13px;color:var(--muted)}
.math-doodle{position:absolute;z-index:2;display:grid;place-items:center;border-radius:50%;font-weight:900}
.doodle-one{right:-22px;top:4px;width:64px;height:64px;background:var(--coral);font-size:34px;transform:rotate(9deg)}
.doodle-two{left:8px;top:2px;width:48px;height:48px;background:var(--aqua);font-size:24px;transform:rotate(-8deg)}
.section{padding:92px 0;border-top:0}
.section:nth-of-type(2n){background:#fff}
.section h2{font-size:clamp(38px,5vw,64px);line-height:1;letter-spacing:-.05em;margin:0 0 26px;max-width:900px}
.section-intro{font-size:20px;max-width:760px;color:#4e493f;margin:0 0 52px}
.grade-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px}
.grade{padding:32px;border:2px solid var(--ink);border-radius:24px;min-height:250px;box-shadow:7px 7px 0 var(--ink)}
.grade+.grade{padding-left:32px;border-left:2px solid var(--ink)}
.grade>span{display:inline-grid;place-items:center;min-width:56px;height:38px;padding:0 10px;border:2px solid var(--ink);border-radius:999px;background:#fff;font-size:14px;font-weight:900;margin-bottom:30px}
.grade-yellow{background:#fff3ad}.grade-blue{background:#dcecff}.grade-coral{background:#ffd9d2}
.grade h3{font-size:26px;margin:0 0 14px;letter-spacing:-.03em}
.grade p{margin:0;color:#514c43}
.split{display:grid;grid-template-columns:1fr 1fr;gap:72px;align-items:center}
.split.reverse .split-media{order:2}
.split-media{padding:18px;border-radius:28px;transform:rotate(-1.2deg)}
.split-media img{width:100%;aspect-ratio:5/4;object-fit:cover;border-radius:20px}
.media-aqua{background:var(--aqua)}.media-yellow{background:var(--yellow);transform:rotate(1.2deg)}
.check-list{display:grid;gap:0;margin:32px 0 0;padding:0;list-style:none;border-top:1px solid var(--ink)}
.check-list li{padding:17px 0;border-bottom:1px solid var(--line);font-size:17px}
.triple{display:grid;grid-template-columns:repeat(3,1fr);gap:18px;background:transparent;border:0}
.triple article{background:#fff;padding:34px;min-height:260px;border:2px solid var(--line);border-radius:22px}
.triple article:nth-child(1){border-top:8px solid var(--aqua)}.triple article:nth-child(2){border-top:8px solid var(--yellow)}.triple article:nth-child(3){border-top:8px solid var(--coral)}
.triple h3{font-size:25px;line-height:1.1;margin:0 0 14px;letter-spacing:-.03em}
.visual-band{padding:0;background:var(--purple)}
.visual-grid{display:grid;grid-template-columns:1.2fr .8fr}
.visual-grid img{width:100%;height:520px;object-fit:cover;filter:saturate(1.05)}
.visual-copy{background:var(--purple);color:#fff;padding:64px;display:flex;flex-direction:column;justify-content:center}
.visual-copy h2{font-size:48px;line-height:1;letter-spacing:-.05em;margin:0 0 24px}
.visual-copy p{font-size:20px;margin:0 0 28px}
.visual-copy .btn{align-self:flex-start}
.blog-preview{display:grid;grid-template-columns:1.2fr .8fr;gap:60px}
.blog-feature img{aspect-ratio:16/10;object-fit:cover;margin-bottom:22px;border-radius:22px}
.blog-feature h3{font-size:34px;line-height:1.06;letter-spacing:-.04em;margin:0 0 10px}
.blog-feature p{color:#514c43;margin:0 0 16px}
.blog-list{border-top:1px solid var(--ink)}
.blog-row{display:block;padding:22px 16px;border-bottom:1px solid var(--line);border-radius:14px;transition:.18s ease}
.blog-row:hover{background:#f2efff;transform:translateX(4px)}
.blog-row strong{display:block;font-size:20px;margin-bottom:6px}
.blog-row span{color:var(--muted);font-size:14px}
.faq-list{border-top:1px solid var(--ink);max-width:900px}
.faq-item{border-bottom:1px solid var(--line)}
.faq-question{width:100%;border:0;background:transparent;text-align:left;padding:22px 42px 22px 0;font:inherit;font-size:19px;font-weight:750;cursor:pointer;position:relative;color:var(--ink)}
.faq-question:after{content:'+';position:absolute;right:0;top:20px;font-size:26px;font-weight:400}
.faq-item.open .faq-question:after{content:'–'}
.faq-answer{display:none;padding:0 50px 22px 0;color:#514c43;max-width:760px}
.faq-item.open .faq-answer{display:block}
.cta{background:var(--yellow);padding:86px 0;position:relative;overflow:hidden}
.cta:after{content:'×  +  π  ÷';position:absolute;right:4%;top:4px;color:rgba(34,32,79,.09);font-size:100px;font-weight:900;letter-spacing:.08em;white-space:nowrap}
.cta-inner{display:flex;align-items:end;justify-content:space-between;gap:40px}
.cta h2{font-size:clamp(44px,6vw,74px);line-height:.96;letter-spacing:-.055em;max-width:780px;margin:0}
.site-footer{border-top:1px solid var(--line);padding:54px 0 22px;background:#24214f;color:#fff}
.footer-grid{display:flex;justify-content:space-between;gap:40px}
.footer-grid p{color:#c9c6df;margin:10px 0 0}
.footer-links{display:grid;grid-template-columns:repeat(2,max-content);gap:10px 28px;font-size:14px}
.footer-bottom{margin-top:38px;padding-top:20px;border-top:1px solid rgba(255,255,255,.14);font-size:11px;color:#aaa6c7;display:flex;gap:12px;flex-wrap:wrap}
.footer-bottom a:hover{color:#fff;text-decoration:underline}

/* Blog */
.blog-hero{padding:82px 0 54px}
.blog-hero h1{font-size:clamp(52px,7vw,88px);line-height:.95;letter-spacing:-.06em;margin:0 0 20px;max-width:900px}
.blog-hero p{font-size:21px;color:#514c43;max-width:720px;margin:0}
.blog-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:46px 30px;padding-bottom:92px}
.post-card img{aspect-ratio:16/10;object-fit:cover;margin-bottom:18px;border-radius:22px}
.post-card:hover img{transform:translateY(-4px);box-shadow:0 12px 28px rgba(51,38,116,.18)}
.post-card img{transition:.2s ease}
.post-card h2{font-size:30px;line-height:1.05;letter-spacing:-.04em;margin:0 0 10px}
.post-card p{margin:0;color:#514c43}
.post-card .meta{font-size:13px;color:var(--muted);margin-top:14px}
.article-hero{padding:68px 0 38px}
.article-hero .article-kicker{font-size:14px;color:var(--muted);margin-bottom:20px}
.article-hero h1{font-size:clamp(48px,6.6vw,82px);line-height:.96;letter-spacing:-.06em;margin:0 0 20px;max-width:980px}
.article-hero .dek{font-size:21px;max-width:760px;color:#514c43;margin:0 0 18px}
.article-meta{font-size:13px;color:var(--muted)}
.article-hero-image{width:min(calc(100% - 40px),var(--max));margin:22px auto 64px;aspect-ratio:21/9;object-fit:cover}
.article-layout{width:min(calc(100% - 40px),var(--max));margin:0 auto 100px;display:grid;grid-template-columns:180px minmax(0,var(--article)) 220px;gap:44px;align-items:start;justify-content:center}
.article-toc,.author-card{position:sticky;top:106px}
.article-toc{border-top:1px solid var(--ink);padding-top:14px}
.article-toc strong,.author-card strong{font-size:13px;text-transform:uppercase;letter-spacing:.08em}
.article-toc nav{display:grid;margin-top:14px}
.article-toc a{font-size:13px;color:#625c50;padding:7px 0}
.article-toc a:hover{color:var(--ink)}
.author-card{border-top:1px solid var(--ink);padding-top:14px}
.author-card p{font-size:14px;color:#625c50}
.article-body{font-family:Georgia,"Times New Roman",serif;font-size:20px;line-height:1.72}
.article-body h2{font-family:Inter,ui-sans-serif,system-ui,sans-serif;font-size:38px;line-height:1.03;letter-spacing:-.04em;margin:64px 0 20px}
.article-body h3{font-family:Inter,ui-sans-serif,system-ui,sans-serif;font-size:26px;line-height:1.1;margin:38px 0 14px}
.article-body p{margin:0 0 24px}
.article-body ul{padding-left:22px}
.article-body img{margin:42px 0;width:100%}
.article-note{border-left:4px solid var(--yellow);padding:20px 24px;background:var(--paper-2);margin:34px 0;font-family:Inter,ui-sans-serif,system-ui,sans-serif;font-size:17px}
.article-cta{margin-top:64px;background:var(--yellow);padding:34px;font-family:Inter,ui-sans-serif,system-ui,sans-serif}
.article-cta h3{margin:0 0 10px;font-size:30px}
.related{border-top:1px solid var(--line);padding:72px 0}
.related h2{font-size:36px;letter-spacing:-.04em}
.related-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:26px}
.related-grid article{border-top:1px solid var(--ink);padding-top:16px}
.related-grid h3{font-size:22px;margin:0 0 8px}
.related-grid p{color:var(--muted);font-size:14px;margin:0}

@media (max-width:980px){
  .hero-grid,.split,.blog-preview,.visual-grid{grid-template-columns:1fr}
  .hero-visual{max-width:650px}.hero-image{aspect-ratio:16/10;border-radius:34px}
  .visual-grid img{height:420px}
  .grade-grid,.triple{grid-template-columns:1fr}
  .grade+.grade{padding-left:0;border-left:0}
  .article-layout{grid-template-columns:1fr;max-width:780px}
  .article-toc,.author-card{position:static}
  .article-toc nav{grid-template-columns:repeat(2,1fr);gap:0 20px}
  .author-card{border-bottom:1px solid var(--line);padding-bottom:18px}
}
@media (max-width:720px){
  .shell{width:min(calc(100% - 28px),var(--max))}
  .nav-inner{min-height:66px}
  .text-logo{font-size:16px}
  .nav-links{gap:14px}.nav-links>a:first-child{display:none}
  .nav-cta{padding:10px 13px;font-size:13px}
  .hero{padding:50px 0 52px}.hero-grid{gap:34px}.hero p,.section-intro,.blog-hero p,.article-hero .dek{font-size:18px}.hero-visual{padding:16px 10px 32px 22px}.hero-note{left:2px}.doodle-one{right:-4px}
  .section{padding:64px 0}.split{gap:34px}.visual-copy{padding:40px 24px}.visual-grid img{height:330px}
  .triple article{min-height:auto;padding:28px}.blog-grid{grid-template-columns:1fr}.cta{padding:58px 0}.cta-inner{align-items:flex-start;flex-direction:column}
  .footer-grid{flex-direction:column}.footer-links{grid-template-columns:1fr 1fr}.footer-bottom{gap:9px}
  .article-hero{padding-top:48px}.article-hero-image{width:calc(100% - 28px);aspect-ratio:16/9;margin-bottom:44px}
  .article-layout{width:calc(100% - 28px);gap:28px}.article-body{font-size:18px}.article-body h2{font-size:32px}.related-grid{grid-template-columns:1fr}.article-toc nav{grid-template-columns:1fr}
}