:root{font-family:Inter,Arial,sans-serif;color:#182b25;background:#f5f7f8;font-synthesis:none;--green:#182b25;--lime:#d7f96b;--muted:#626e68;--line:#e0e6e3}*{box-sizing:border-box}body{margin:0}button,a,summary{-webkit-tap-highlight-color:transparent}button,select{font:inherit}button,a,summary{touch-action:manipulation}button{cursor:pointer}a{color:inherit;text-decoration:none}button:focus-visible,a:focus-visible,summary:focus-visible,select:focus-visible{outline:3px solid #75972c;outline-offset:4px}.skip{position:fixed;top:-80px;background:white;padding:16px;z-index:10}.skip:focus{top:0}.sidebar{position:fixed;inset:0 auto 0 0;width:256px;background:var(--green);color:#fff;padding:38px 22px;display:flex;flex-direction:column}.brand{display:flex;align-items:center;gap:12px;font-weight:800;letter-spacing:.5px;font-size:21px}.brand-icon{display:grid;place-items:center;background:var(--lime);color:var(--green);width:42px;height:44px;border-radius:12px;font-family:Georgia,serif;font-size:34px}.brand small{display:block;color:#b6c6bd;letter-spacing:0;font-size:12px;font-weight:400;margin-top:6px}.eyebrow{font-size:12px;letter-spacing:1.6px;text-transform:uppercase;font-weight:700}.sidebar>.eyebrow{margin:50px 14px 16px;color:#a6bab0}nav{display:grid;gap:8px}nav a{display:flex;align-items:center;gap:13px;padding:15px 13px;border-radius:9px;color:#c8d5ce;font-size:15px}nav a:hover{background:#283d33}nav a.active{background:var(--lime);color:var(--green);font-weight:700}.nav-icon{font-size:21px;width:23px;text-align:center}.side-bottom{margin-top:auto;padding:30px 14px 0}.mini-grid{border:1px solid #42584b;border-radius:8px;padding:20px 8px;text-align:center;font:italic 23px Georgia;color:#d7f96b;background-image:linear-gradient(#ffffff08 1px,transparent 1px),linear-gradient(90deg,#ffffff08 1px,transparent 1px);background-size:17px 17px}.side-bottom p{font-size:14px;line-height:1.7;color:#b6c6bd}.author{border-top:1px solid #3a4d42;margin-top:30px;padding-top:22px;font-size:14px}.author small{display:block;color:#a6bab0;font-size:12px;margin-top:7px}.shell{margin-left:256px}header{height:86px;display:flex;align-items:center;justify-content:space-between;padding:0 48px;border-bottom:1px solid var(--line);background:white}#breadcrumb{font-size:14px;color:var(--muted)}.language{display:flex;border:1px solid var(--line);padding:4px;border-radius:9px;gap:3px}.language button{border:0;background:none;font-size:12px;font-weight:700;padding:9px 12px;border-radius:5px;color:#58675e}.language button.active{background:var(--green);color:white}main{max-width:1440px;margin:auto;padding:42px 48px 56px;min-height:calc(100vh - 150px)}.intro{display:flex;justify-content:space-between;align-items:center;gap:24px;margin-bottom:30px}.intro .eyebrow{color:#66843c;font-size:12px;margin-bottom:13px}h1{font-size:clamp(28px,3vw,40px);letter-spacing:-1.1px;margin:0 0 12px;font-weight:750;line-height:1.2}.sub{color:var(--muted);font-size:16px;line-height:1.65;margin:0;max-width:650px}.number{font:52px Georgia;letter-spacing:-2px}.count{min-width:116px;text-align:right;color:#344f3b}.count small{display:block;font:13px Arial;letter-spacing:0;margin-top:5px}.feature{background:var(--green);color:white;border-radius:15px;padding:26px 30px;display:grid;grid-template-columns:1fr 1fr;align-items:center;gap:24px;margin-bottom:32px;overflow:hidden}.feature .eyebrow{color:var(--lime)}.feature h2{font-size:21px;margin:12px 0}.feature p{font-size:14px;line-height:1.6;color:#d2ded5;margin:0}.feature-math{font:italic 39px Georgia;text-align:center;padding:24px 12px;color:var(--lime);background-image:linear-gradient(#ffffff0a 1px,transparent 1px),linear-gradient(90deg,#ffffff0a 1px,transparent 1px);background-size:25px 25px;border-left:1px solid #456047}.section-bar{display:flex;justify-content:space-between;align-items:center;gap:18px;margin:24px 0}.section-bar h2{font-size:21px;margin:0}.chips{display:flex;gap:8px;flex-wrap:wrap}.chips button{border:1px solid var(--line);background:white;border-radius:8px;padding:11px 16px;font-size:14px;color:#4c5d52}.chips button.active{background:var(--green);border-color:var(--green);color:white}.grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:18px}.card{background:white;border:1px solid var(--line);border-radius:12px;padding:23px;min-width:0;transition:border-color .18s,transform .18s}.card:hover{border-color:#9aaf9e}.card-top{display:flex;align-items:center;justify-content:space-between;margin-bottom:20px}.tag{font-size:12px;background:#eef4ea;color:#506d34;padding:6px 9px;border-radius:5px}.card-number{color:#8a9790;font-size:12px;font-variant-numeric:tabular-nums}.card h3{font-size:17px;line-height:1.45;margin:0 0 13px}.formula{font:23px/1.7 Georgia,'Times New Roman',serif;min-height:55px;color:#1d442e;overflow-wrap:anywhere}.card p{font-size:14px;line-height:1.65;color:var(--muted);margin:12px 0}.card details{border-top:1px solid var(--line);margin-top:18px;padding-top:15px}.card summary{cursor:pointer;font-size:14px;font-weight:600;line-height:1.5}.card details p{background:#f4f7f1;padding:13px;border-radius:6px;color:#354d3b}.notice{background:#edf2e8;color:#435437;padding:16px 20px;border-radius:9px;font-size:14px;line-height:1.7;margin:22px 0}.resource{display:flex;flex-direction:column}.resource .resource-logo{font:bold 25px Georgia;width:50px;height:50px;background:#e9efff;color:#3452a0;border-radius:12px;display:grid;place-items:center;margin-bottom:20px}.resource:nth-child(2n) .resource-logo{background:#f2eefd;color:#725399}.resource .links{margin-top:auto;padding-top:20px;display:flex;flex-wrap:wrap;gap:10px}.link-button{display:inline-block;padding:11px 15px;border:1px solid #b5c4b5;border-radius:7px;color:var(--green);font-size:14px;font-weight:600}.link-button:hover{background:#eaf3df}.resource-meta{font-size:13px;color:#62745d;margin:8px 0 15px}.book-list{display:grid;gap:13px}.book-row{background:white;border:1px solid var(--line);border-radius:11px;padding:23px;display:flex;justify-content:space-between;align-items:center;gap:20px}.book-row h3{margin:0 0 8px;font-size:18px}.book-row p{margin:0;font-size:14px;color:var(--muted);line-height:1.6}.book-symbol{height:61px;min-width:51px;background:#dcecc5;border-left:4px solid #a4bc88;border-radius:2px 7px 7px 2px;display:grid;place-items:center;font:24px Georgia}.book-info{display:flex;gap:22px;align-items:center}.book-links{display:flex;gap:9px;flex-wrap:wrap}.source-note{font-size:13px;line-height:1.7;color:var(--muted);margin-top:28px}.source-note a{text-decoration:underline}.problem .question{font-size:16px;color:#253c2e;min-height:65px}.problem .formula{font-size:20px}footer{border-top:1px solid var(--line);margin:0 48px;padding:21px 0;display:flex;justify-content:space-between;gap:20px;font-size:12px;color:#758078}@media(min-width:1500px){.grid{grid-template-columns:repeat(4,minmax(0,1fr))}}@media(max-width:1200px){.grid{grid-template-columns:repeat(2,minmax(0,1fr))}.sidebar{width:230px;padding:32px 17px}.shell{margin-left:230px}header{padding:0 30px}main{padding:32px 30px}.section-bar{align-items:flex-start;flex-direction:column}.book-row{align-items:flex-start;flex-direction:column}}@media(max-width:760px){.sidebar{position:static;width:auto;padding:18px 20px 0;background:var(--green)}.brand{font-size:19px}.brand-icon{width:36px;height:38px;font-size:30px}.sidebar>.eyebrow,.side-bottom{display:none}nav{display:grid;grid-template-columns:repeat(4,1fr);gap:4px;margin:18px -12px 0}nav a{padding:13px 4px;gap:5px;flex-direction:column;border-radius:8px 8px 0 0;text-align:center;font-size:12px}nav .nav-icon{font-size:20px}.shell{margin-left:0}header{height:61px;padding:0 20px}main{padding:27px 20px 35px}h1{font-size:29px}.intro{margin-bottom:23px;gap:8px}.count{min-width:65px}.number{font-size:37px}.count small{font-size:12px}.sub{font-size:15px}.feature{padding:22px;grid-template-columns:1fr;gap:12px}.feature h2{font-size:19px}.feature-math{border-left:0;border-top:1px solid #456047;font-size:32px;padding:17px}.grid{gap:13px}.card{padding:19px}.chips{gap:6px}.chips button{padding:10px 12px}.book-row{padding:20px}.book-info{gap:15px}.book-links{width:100%}footer{margin:0 20px;flex-direction:column;gap:8px}}@media(max-width:500px){.grid{grid-template-columns:1fr}.card .formula{font-size:25px}.intro{align-items:flex-start}.intro .count{display:none}.book-links .link-button{font-size:13px}}@media(prefers-reduced-motion:reduce){*{transition:none!important}}
/* ALL MATH mobile reference direction */
:root{--green:#1688da;--lime:#dff3ff;--muted:#60788b;--line:#d8e7ef;color:#143750;background:#f2f8fb}.sidebar{background:#fff;color:#173e57;border-right:1px solid var(--line);padding-top:28px;overflow-y:auto}.brand{color:#13adbf}.brand-icon{background:#16b4c6;color:white}.brand small{color:#657e8c;font-size:10px;letter-spacing:1px}.sidebar>.eyebrow{color:#7a929f;margin-top:32px}.sidebar nav a{color:#36596f;padding:11px 12px}.sidebar nav a.active{background:#e0f2ff;color:#087bc9}.sidebar nav a:hover{background:#eff8fe}.side-bottom{padding-top:25px}.mini-grid{background-color:#f4fbff;border-color:#d5eaf4;color:#2192bf}.side-bottom p,.author small{color:#617f91}.author{border-color:#dcebf1}header{background:#319eea;color:#fff;height:72px}#breadcrumb{color:white;font-weight:600}.language{background:#ffffff20;border-color:#ffffff50}.language button{color:white}.language button.active{background:white;color:#1788ce}main{max-width:1260px;padding-top:32px}h1{font-size:32px;letter-spacing:-.5px}.intro .eyebrow{color:#119dad}.intro{margin-bottom:30px}.feature{background:#177dcc}.feature-math,.feature .eyebrow{color:white}.feature p{color:#e1f3ff}.count{color:#1688da}.card{border-radius:12px;box-shadow:0 3px 12px #235c7610}.card:hover{border-color:#84bddb}.formula{color:#1e719f}.tag{background:#e4f4ff;color:#2a749f}.chips button.active{background:#1688da;border-color:#1688da}.card details p,.notice{background:#eaf6ff;color:#345b73}.home-group{margin:26px 0 32px}.home-group h2{font-size:18px;font-weight:650;margin:0 0 14px}.tile-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:19px}.tile{background:white;border:1px solid #c8dfe9;border-radius:12px;overflow:hidden;box-shadow:0 4px 14px #22557309;transition:transform .18s,border-color .18s}.tile:hover{transform:translateY(-3px);border-color:#4aa8d8}.tile-art{height:130px;display:flex;justify-content:center;align-items:center;font:600 59px Georgia,serif;color:#fff;background:linear-gradient(120deg,#17b9d4,#1688da);letter-spacing:3px}.tile:nth-child(2n) .tile-art{background:linear-gradient(120deg,#366adc,#6586f1)}.home-group:nth-of-type(3) .tile-art{background:#7258c3}.home-group:nth-of-type(3) .tile:nth-child(2n) .tile-art{background:#e52961}.home-group:nth-of-type(4) .tile-art{background:linear-gradient(120deg,#147daa,#3da7d9)}.home-group:nth-of-type(5) .tile-art{background:linear-gradient(120deg,#3aa9ab,#69babe)}.tile-copy{padding:17px 20px;position:relative}.tile h3{font-size:17px;margin:0;line-height:1.5}.tile p{font-size:14px;color:#668194;line-height:1.6;margin:5px 0 0}.tile small{position:absolute;right:15px;top:17px;color:#60869d}.resources{grid-template-columns:repeat(3,minmax(0,1fr))}.resources .tile-art{height:125px}.resources .tile:nth-child(3n) .tile-art{background:linear-gradient(120deg,#32acb2,#5bc3cc)}.book-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:18px}.book-card{background:#fff;border:1px solid #cbdfe9;border-radius:10px;overflow:hidden;display:flex;flex-direction:column}.book-card:hover{border-color:#269cdb;box-shadow:0 5px 20px #1688da18}.cover-wrap{background:#e9f2f7;display:grid;place-items:center;padding:15px;height:223px}.cover-wrap img{height:193px;width:100%;object-fit:contain;filter:drop-shadow(3px 4px 3px #23445225)}.cover-wrap>span{font:70px Georgia;color:#319ed0}.book-copy{padding:16px;display:flex;flex-direction:column;flex:1}.book-copy h3{font-size:15px;line-height:1.55;margin:12px 0 0;overflow-wrap:anywhere}.book-copy p{font-size:13px;color:#7890a0;margin:8px 0 13px}.book-copy .tag{align-self:flex-start}.book-open{font-size:13px;font-weight:600;color:#1685bd;margin-top:auto}.back-link{display:inline-block;margin:0 0 25px;border:1px solid #aed8ee;padding:10px 15px;background:white;border-radius:8px;color:#1883ba;font-size:14px}.shapes{display:flex;flex-wrap:wrap;gap:15px}.shapes button{font:50px Georgia;width:80px;height:85px;border:1px solid #bdd9e9;border-radius:10px;background:#eef8ff;color:#2197ca}.shapes button[aria-pressed=true]{background:#198fce;color:white}.self-check{margin-top:24px}.author-card{max-width:670px;text-align:center;padding:42px}.avatar{display:grid;place-items:center;width:82px;height:82px;background:#1caec8;border-radius:24px;color:white;font-size:30px;font-weight:700;margin:0 auto 25px}.author-card h2{line-height:1.5}.contact-links{display:flex;gap:12px;justify-content:center;flex-wrap:wrap;margin-top:24px}.contact-links a{padding:12px 17px;background:#eaf7ff;color:#147cad;border-radius:8px;font-size:15px}footer{color:#678496}@media(max-width:1100px){.book-grid{grid-template-columns:repeat(3,minmax(0,1fr))}.resources{grid-template-columns:repeat(2,minmax(0,1fr))}}@media(max-width:760px){.sidebar{padding:15px 16px 0;background:white;border-right:0}.sidebar nav{display:flex;overflow-x:auto;margin:14px -16px 0;padding:0 10px;gap:5px}.sidebar nav a{flex:0 0 auto;flex-direction:row;white-space:nowrap;padding:13px 10px;font-size:13px;border-radius:8px 8px 0 0}.sidebar nav .nav-icon{width:auto;font-size:17px}.sidebar .brand{font-size:20px}.brand small{font-size:9px}header{height:57px;padding:0 16px}main{padding:24px 16px 36px}h1{font-size:27px}.intro .sub{font-size:14px}.tile-grid{gap:13px}.tile-art{height:107px;font-size:47px}.tile-copy{padding:12px}.tile h3{font-size:15px}.tile p{font-size:12px;line-height:1.55}.tile small{display:none}.home-group{margin-bottom:26px}.home-group h2{font-size:16px}.book-grid{grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}.cover-wrap{height:205px;padding:12px}.cover-wrap img{height:181px}.book-copy{padding:12px}.book-copy h3{font-size:14px}.resources .tile-art{height:106px}.book-copy .tag{font-size:12px}.source-note{font-size:13px}.author-card{padding:28px 17px}.author-card h2{font-size:21px}.shapes{gap:8px}.shapes button{width:52px;height:62px;font-size:38px}.count{display:none}}@media(max-width:360px){.tile h3{font-size:14px}.tile-copy{padding:10px}.cover-wrap{height:174px}.cover-wrap img{height:150px}}
.reader-toolbar{display:flex;align-items:center;justify-content:space-between;gap:16px;margin:0 0 18px;flex-wrap:wrap}.reader-toolbar span{font-size:14px;color:var(--muted)}.formula-reader{width:100%;height:75vh;min-height:480px;background:#fff;border:1px solid var(--line);border-radius:12px;overflow:hidden}.formula-reader iframe{display:block;width:100%;height:100%;border:0}.topic-card{display:flex;flex-direction:column}.topic-card h2{font-size:18px;line-height:1.5;margin:0 0 8px}.topic-card p{margin:0 0 22px}.pdf-actions{display:flex;align-items:center;flex-wrap:wrap;gap:16px;margin-top:auto}.download-link{font-size:14px;color:#1685bd;text-decoration:underline;text-underline-offset:4px}.literacy-empty{max-width:700px;padding:32px}.literacy-empty h2{line-height:1.5}.literacy-empty .link-button{margin-top:16px}@media(max-width:760px){.formula-reader{height:70vh;min-height:440px}.reader-toolbar{gap:12px}.topic-card h2{font-size:17px}.literacy-empty{padding:23px}}
.reference-picture{display:block;position:relative;width:100%;overflow:hidden;background:#f0f7f5;flex-shrink:0}.reference-picture img{display:block;position:absolute;max-width:none;object-fit:fill}.tile>.reference-picture{border-radius:0}.tile{background:#f0f7f5;border-color:#71938a}.tile-copy{background:#f0f7f5}.tile-copy h3{font-weight:650}.brand-icon{width:45px;height:38px;background:white;overflow:hidden;border-radius:0}.brand-icon .reference-picture{width:45px}.author-card>.reference-picture{margin:-42px -42px 28px;width:calc(100% + 84px)}.author-card{overflow:hidden}.reference-formula-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:14px;margin-bottom:24px}.reference-formula-grid figure{margin:0;border:1px solid #91aca4;border-radius:10px;overflow:hidden;background:#f0f7f5}.reference-formula-grid figcaption{padding:12px;font-size:14px;font-weight:600}.test-reference{max-width:300px;margin-bottom:20px}.tile>.reference-picture:has(img[src$="screen-3.jpg"]){max-height:none}@media(max-width:760px){.reference-formula-grid{grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}.author-card>.reference-picture{margin:-28px -17px 24px;width:calc(100% + 34px)}.brand-icon,.brand-icon .reference-picture{width:36px}.brand-icon{height:30px}}
.formula-book-link{display:block}.formula-book-link:hover{background:#def3ff}.page-reader{border:1px solid #cbdae3;border-radius:12px;overflow:hidden;background:#e8eef2}.page-tools{display:flex;align-items:center;justify-content:center;flex-wrap:wrap;gap:12px;padding:16px;background:white;border-bottom:1px solid #d6e1e8}.page-tools button,.page-tools select{font:inherit;border:1px solid #b7d2e2;border-radius:7px;padding:10px 13px;background:white;color:#185c85}.page-tools button:disabled{opacity:.4;cursor:default}.page-tools label,.page-tools a{font-size:14px}.page-tools a{color:#1685bd;text-decoration:underline}.page-stage{overflow:auto;max-height:78vh;padding:22px;touch-action:pan-y pinch-zoom;overscroll-behavior:contain}.page-sheet{width:min(100%,780px);margin:auto;box-shadow:0 7px 25px #23435233;transform-origin:left center;background:white}.page-sheet img{display:block;width:100%;height:auto;max-width:none;user-select:none}.page-sheet.zoomed{width:1560px;max-width:none;margin:0}.page-stage:has(.zoomed){touch-action:pan-x pan-y pinch-zoom}.page-status{text-align:center;font-size:14px;color:#46677c;padding:14px;margin:0;background:#f8fbfd}@media(max-width:760px){.page-stage{padding:8px;max-height:72vh}.page-tools{gap:8px;padding:10px}.page-tools button,.page-tools select{font-size:14px;padding:10px}.page-sheet.zoomed{width:1000px}}
.reference-formula-grid figcaption small{display:block;font-size:12px;font-weight:400;color:#577d92;margin-top:7px}.page-tools button:focus-visible{outline:3px solid #246dba}.formula-book-link{height:100%}