:root{--paper:#f1f5ff;--ink:#182b55;--lime:#72e1ef}html{scroll-behavior:smooth;scroll-padding-top:90px}body{background:var(--paper);color:var(--ink)}header{gap:24px}header nav{display:flex;gap:24px;font-size:13px}header nav a{text-decoration:none}.math-hero{display:grid;grid-template-columns:1.05fr 1fr;gap:60px;align-items:center;padding-top:75px;padding-bottom:70px}.math-hero h1{font-size:clamp(48px,6.4vw,92px);line-height:1.02;letter-spacing:-4px;margin:25px 0}.math-hero h1 em{font-family:Georgia,serif;font-weight:400}.intro{max-width:500px;line-height:1.8;font-size:16px}.hero-art{position:relative;min-height:440px;background:#dce9ff;border-radius:48% 48% 12px 12px;display:flex;align-items:center}.hero-art>img:not(.spark){width:100%;animation:float 8s ease-in-out infinite}.hero-art .spark{position:absolute;width:125px;bottom:-15px;right:-5px}.art-tag{position:absolute;top:35px;width:100%;text-align:center;font-size:10px;letter-spacing:2px}.formula-sticker{position:absolute;bottom:15px;left:-20px;background:#ffb29c;transform:rotate(-5deg);padding:23px 25px;font:24px Georgia,serif;box-shadow:0 9px 22px #182b5512}.formula-sticker small{font-size:15px}.hero-meta{display:flex;gap:36px;margin-top:45px}.hero-meta>span{font-family:Georgia,serif;font-size:28px}.hero-meta small{display:block;font:9px Arial,sans-serif;letter-spacing:1px;margin-top:7px}.ticker{padding:20px 5%;background:var(--ink);color:var(--lime);font-size:13px;letter-spacing:2px;display:flex;gap:32px;justify-content:center;flex-wrap:wrap}.ticker span{font-size:18px}.course-grid{display:grid;grid-template-columns:1fr 1fr;gap:22px}.course{display:block;padding:35px;text-decoration:none;color:var(--ink);border-radius:8px;transition:transform .2s}.course:hover{transform:translateY(-5px)}.course3{background:#dce9ff}.course5{background:#ffe1d8}.course-no{font:50px Georgia,serif;display:flex;gap:22px;align-items:center}.course-no span{font:10px Arial,sans-serif;letter-spacing:2px}.course h3{font:clamp(29px,3vw,44px)/1.1 Georgia,serif;margin:30px 0 22px}.course p{font-size:14px;line-height:1.8;max-width:450px}.course-footer{border-top:1px solid #182b5533;margin-top:30px;padding-top:22px;display:flex;gap:15px;justify-content:space-between;flex-wrap:wrap;font-size:11px}.course-footer b{font-size:13px}.drive-shell{height:720px;background:#e2e5dc;border:1px solid #182b5533;border-radius:8px;overflow:hidden;position:relative}.drive-shell iframe{width:100%;height:100%;border:0}.drive-shell #exitMath5{display:none;position:absolute;top:12px;right:18px;background:var(--paper)}.drive-shell:fullscreen{height:100vh;background:var(--paper)}.drive-shell:fullscreen #exitMath5,.drive-shell.expanded #exitMath5{display:block}.drive-shell.expanded{position:fixed;inset:0;z-index:1000;height:100dvh;border-radius:0}.playground{display:grid;grid-template-columns:1fr 1.1fr;gap:70px;background:#e3ecff;max-width:none;padding-left:max(5%,calc((100vw - 1200px)/2));padding-right:max(5%,calc((100vw - 1200px)/2))}.playground label{display:block;margin:22px 0;font-size:13px}.playground output{float:right}.playground input[type=range]{display:block;width:100%;accent-color:var(--ink);margin-top:14px}.playground .check{display:flex;gap:10px;align-items:center}.graph-panel{align-self:center;background:var(--ink);padding:22px;border-radius:12px;color:var(--lime)}.graph-panel svg{display:block;width:100%}.graph-panel p{text-align:center;font:22px Georgia,serif}.legend{display:flex;gap:22px;justify-content:center;font-size:11px}.legend span:last-child{color:#ffb29c}.number-row{display:grid;grid-template-columns:repeat(3,1fr);gap:12px}.number-row input{width:100%;min-width:0}.number-row label{display:block}.method-strip{display:grid;grid-template-columns:repeat(4,1fr);gap:25px;margin-top:40px;padding:30px 0;border-top:1px solid #182b5533;font-size:12px;line-height:2}.chapter-cards{display:grid;grid-template-columns:repeat(3,1fr);gap:15px}.chapter-cards button{text-align:left;background:transparent;border:1px solid #182b5533;color:inherit;padding:24px;border-radius:6px;min-height:150px;cursor:pointer}.chapter-cards button:hover{background:#dce9ff}.chapter-cards b{display:block;font:21px/1.3 Georgia,serif;margin:13px 0}.chapter-cards span{font-size:11px}.closing{background:#dce9ff;display:flex;gap:65px;align-items:center;border-radius:12px;margin-bottom:70px}.closing img{width:190px}.closing p{max-width:600px;line-height:1.8}.reader-main{min-width:0}button,a,input{touch-action:manipulation}a:focus-visible,button:focus-visible,input:focus-visible{outline:3px solid #176ec8;outline-offset:4px}.dark{--paper:#0c1730;--ink:#e8efff;--lime:#72e1ef}.dark .hero-art,.dark .course3,.dark .playground{background:#162747}.dark .course5,.dark .closing{background:#392b3c}.dark .ticker,.dark .graph-panel{background:#0c1935}.dark .course,.dark .chapter-cards button{color:#e8efff}.dark .formula-sticker{color:#182b55}.dark .chapter-cards button:hover{background:#162747}@keyframes float{50%{transform:translateY(-8px)}}@media(min-width:1600px){.math-hero{gap:110px}.hero-art{min-height:480px}}@media(max-width:850px){header nav{gap:14px}.math-hero{gap:25px}.math-hero h1{letter-spacing:-2px}.hero-art{min-height:330px}.hero-art .spark{width:95px}.hero-meta{gap:22px}.playground{gap:25px}.chapter-cards{grid-template-columns:repeat(2,1fr)}.closing{gap:25px}.closing img{width:125px}}@media(max-width:600px){header{flex-wrap:wrap;padding:16px 5%;gap:15px}header nav{order:3;width:100%;justify-content:space-between;font-size:11px}header .brand{flex:1}section{padding-top:50px;padding-bottom:50px}.math-hero{grid-template-columns:1fr;padding-top:40px;gap:50px}.math-hero h1{font-size:58px}.hero-art{min-height:340px;margin:0 12px 15px}.hero-art>img:not(.spark){max-height:350px}.hero-meta{justify-content:space-between;gap:10px}.hero-meta small{font-size:8px}.ticker{gap:12px;font-size:10px;letter-spacing:1px}.course-grid,.playground{grid-template-columns:1fr}.course{padding:26px}.section-head{align-items:flex-start;gap:20px}.drive-shell{height:70dvh;min-height:430px}.chapter-cards{grid-template-columns:1fr}.method-strip{grid-template-columns:1fr 1fr}.closing{flex-direction:column;text-align:center;margin-left:5%;margin-right:5%;padding-left:20px;padding-right:20px}.closing img{width:110px}.number-row{gap:8px}#topicSearch{width:100%}.formula-sticker{left:-10px;font-size:21px}}@media(prefers-reduced-motion:reduce){*{animation:none!important;scroll-behavior:auto!important;transition:none!important}}

header #theme{width:auto;height:auto;min-width:85px;white-space:nowrap;border-radius:30px;padding:11px 15px}header nav{flex:1;justify-content:center}.graph-panel{position:relative}.reader-main:fullscreen{background:var(--paper);overflow:auto;padding:20px}.reader-main.pdf-expanded{background:var(--paper)}

/* Mathematics identity: blueprint blue, cyan and coral. */
.math-hero h1{font-family:Arial,Helvetica,sans-serif;font-weight:650}.math-hero h1 em{color:#2272be}.hero-art{border-radius:16px;background-image:linear-gradient(#182b5508 1px,transparent 1px),linear-gradient(90deg,#182b5508 1px,transparent 1px);background-size:28px 28px}.formula-sticker{transform:rotate(3deg);border-radius:6px}.course{border:1px solid #182b5515}.course-no{font-family:Arial,sans-serif;font-weight:700}.dark .math-hero h1 em{color:#72e1ef}.dark .formula-sticker{color:#182b55}.dark .hero-art{background-image:linear-gradient(#ffffff0a 1px,transparent 1px),linear-gradient(90deg,#ffffff0a 1px,transparent 1px)}header{height:auto;min-height:94px}.legend span:first-child{color:#72e1ef}
/* Keep navigation and introductory copy in separate, spacious rows. */
header{position:relative;z-index:20;min-height:104px;padding-top:22px;padding-bottom:22px;row-gap:22px;background:var(--paper)}
header nav{flex-wrap:wrap;column-gap:28px;row-gap:14px;line-height:1.5}
header nav a{display:inline-flex;align-items:center;min-height:36px;white-space:nowrap}
.math-hero{margin-top:0;padding-top:96px}
.math-hero .eyebrow{line-height:1.8;margin-top:0;margin-bottom:28px}
@media(max-width:850px){header{column-gap:20px}header nav{column-gap:18px}.math-hero{padding-top:76px}}
@media(max-width:600px){header{min-height:0;padding-top:20px;padding-bottom:24px;row-gap:20px}header nav{flex:0 0 100%;justify-content:space-between;column-gap:16px;row-gap:12px;padding-top:10px;border-top:1px solid var(--line)}.math-hero{padding-top:64px}.math-hero .eyebrow{max-width:100%;font-size:9px;letter-spacing:1.6px;line-height:1.9;margin-bottom:26px}}
@media(max-width:340px){header nav{justify-content:flex-start;column-gap:20px;row-gap:10px}.math-hero{padding-top:50px}}
header nav{position:static;inset:auto;z-index:auto;background:transparent;border-bottom:0;padding-bottom:0}
@media(max-width:850px){header{flex-wrap:wrap;height:auto}header nav{position:static;flex:0 0 100%;order:3;width:100%;justify-content:center;padding:16px 0 0;margin-top:4px;border-top:1px solid var(--line)}header .brand{flex:1}header #theme{flex:0 0 auto}.math-hero{clear:both}}