:root{--primary:#5145cd;--navy:#1d2450;--teal:#087f74;--orange:#a44b20;--amber:#996100;--ink:#202334;--sub:#5e6575;--soft:#f5f4fc;--line:#e4e4ed;--white:#fff;--shadow:0 16px 50px rgba(31,31,68,.055)}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:#fff;color:var(--ink);font-family:-apple-system,BlinkMacSystemFont,"Apple SD Gothic Neo","Malgun Gothic","Noto Sans KR",system-ui,sans-serif;line-height:1.7;font-size:16px;letter-spacing:-.018em;word-break:keep-all}button,input,select{font:inherit}button{cursor:pointer}button:focus-visible,input:focus-visible,select:focus-visible{outline:3px solid #a99afc;outline-offset:3px}button:disabled{opacity:.45;cursor:not-allowed}h1,h2,h3,p{margin-top:0}h1,h2,h3{line-height:1.35;color:var(--navy)}.muted{color:var(--sub)}.sm{font-size:13px}.hide{display:none!important}.page{max-width:1500px;margin:auto;padding:0 34px 90px}.topbar{border-bottom:1px solid var(--line);background:rgba(255,255,255,.96);position:sticky;top:0;z-index:30;backdrop-filter:blur(16px)}.top-inner{max-width:1500px;margin:auto;padding:12px 34px;min-height:68px;display:flex;align-items:center;justify-content:space-between;gap:16px}.brand{font-weight:750;color:var(--navy);font-size:21px;display:flex;align-items:center;gap:10px;letter-spacing:-.045em}.brand-mark{display:grid;place-items:center;background:var(--primary);color:#fff;width:31px;height:31px;border-radius:9px;font-size:18px}.toplinks{display:flex;align-items:center;gap:10px;flex-wrap:wrap}.top-caption{font-size:13px;color:var(--sub);margin-right:8px}.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;min-height:45px;border:1px solid var(--line);background:white;border-radius:11px;padding:10px 18px;font-size:14px;font-weight:700;color:var(--navy);transition:background .12s,border .12s;text-align:center;white-space:nowrap}.btn:hover:not(:disabled){background:var(--soft)}.btn.primary{background:var(--primary);border-color:var(--primary);color:white}.btn.primary:hover:not(:disabled){background:#4034b5}.btn.flat{border-color:transparent;background:transparent}.btn.small{padding:8px 12px;min-height:37px}.btn.secondary{border-color:#d7d3fb;color:var(--primary)}.btn.warn{color:var(--orange)}.pill{color:var(--primary);font-size:12px;font-weight:750;letter-spacing:.05em}.intro-wrap{max-width:1060px;margin:70px auto}.intro-heading{padding-bottom:30px;border-bottom:1px solid var(--line)}.intro-heading h1{font-size:clamp(35px,4.2vw,53px);letter-spacing:-.06em;margin:14px 0 18px;font-weight:760}.intro-heading p{font-size:19px;max-width:660px;color:var(--sub)}.select-grid{display:grid;grid-template-columns:1fr 1fr;gap:45px;margin-top:38px}.select-grid h2{font-size:20px;margin-bottom:19px}.grades{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}.grade-button{border:1px solid var(--line);background:white;border-radius:13px;text-align:left;padding:16px 14px;min-height:88px;color:var(--navy);font-weight:750;font-size:23px}.grade-button.selected{border:2px solid var(--primary);padding:15px 13px;background:var(--soft);color:var(--primary)}.grade-button small{display:block;font-size:11px;font-weight:600;color:var(--sub);margin-top:2px}.grade-button:disabled{color:#a6a8b5;background:#fafafa}.sem-button{border:1px solid var(--line);background:white;min-height:69px;width:100%;padding:12px 17px;text-align:left;border-radius:12px;margin-bottom:10px;font-size:17px;font-weight:700;color:var(--navy)}.sem-button.active{border:2px solid var(--primary);background:var(--soft);color:var(--primary);padding:11px 16px}.start-row{margin-top:30px;display:flex;align-items:center;gap:20px;flex-wrap:wrap}.start-row .btn{min-height:54px;padding:13px 29px;font-size:17px}.notice-inline{font-size:14px;color:var(--sub)}.content-head{padding:34px 0 23px;border-bottom:1px solid var(--line);display:flex;justify-content:space-between;align-items:end;gap:22px;flex-wrap:wrap}.content-head h1{font-size:clamp(28px,3vw,35px);margin:7px 0 8px;letter-spacing:-.05em}.content-head p{font-size:14px;margin:0;color:var(--sub)}.chapter-wrap{display:grid;grid-template-columns:258px minmax(0,1fr);gap:35px;margin-top:28px;align-items:start}.sidebar{position:sticky;top:92px;padding-right:15px;border-right:1px solid var(--line);max-height:calc(100vh - 115px);overflow-y:auto}.side-label{font-size:12px;font-weight:750;color:var(--sub);margin:0 0 12px}.side-units{display:flex;flex-direction:column;gap:3px}.side-unit{width:100%;border:0;background:white;text-align:left;display:flex;align-items:center;gap:10px;min-height:49px;padding:11px 9px;font-size:14px;font-weight:650;border-radius:9px;color:#45485c}.side-unit.on{background:var(--soft);color:var(--primary)}.unit-num{width:24px;height:24px;flex:none;border:1px solid #d6d6e6;border-radius:7px;display:grid;place-items:center;font-size:12px}.side-unit.on .unit-num{background:var(--primary);color:#fff;border-color:var(--primary)}.side-title{flex:1;line-height:1.3}.side-tick{font-size:11px;color:var(--teal)}.side-footer{border-top:1px solid var(--line);padding-top:16px;margin-top:18px;color:var(--sub);font-size:12px}.study{min-width:0;max-width:1080px}.chapter-heading{margin-bottom:26px}.chapter-heading h2{font-size:clamp(29px,3vw,39px);margin:7px 0 12px;letter-spacing:-.06em}.chapter-heading p{font-size:17px;color:var(--sub);margin:0}.chapter-rule{height:3px;background:var(--primary);width:56px;margin-bottom:23px}.tabs{display:flex;gap:9px;border-bottom:1px solid var(--line);padding-bottom:11px;margin:25px 0 29px;flex-wrap:wrap}.tab{border:0;background:none;padding:9px 12px;min-height:42px;border-radius:8px;color:var(--sub);font-size:14px;font-weight:700}.tab.active{background:var(--soft);color:var(--primary)}.topic-label{color:var(--primary);font-weight:750;font-size:13px;margin-bottom:12px}.concept{font-size:17px}.concept h3{font-size:24px;margin-bottom:16px}.concept .lead{font-size:18px;line-height:1.85;max-width:860px}.concept-block{margin:31px 0}.concept-block h3{font-size:20px;margin-bottom:12px}.explain-list{padding:0 0 0 21px;max-width:870px}.explain-list li{padding:0 0 10px 5px;line-height:1.8}.visual-panel{background:var(--soft);padding:14px 18px;border-radius:12px;margin:24px 0;max-width:690px}.diagram{width:100%;max-width:630px;min-height:90px;margin:0 auto;display:block}.diagram svg{display:block;width:100%;height:auto;max-height:245px}.example-section{border-top:1px solid var(--line);padding-top:26px;margin-top:35px}.worked{border-left:3px solid var(--primary);padding:3px 0 8px 18px;margin:18px 0 25px;max-width:870px}.worked h4{color:var(--primary);font-size:15px;margin:0 0 5px}.worked p{margin:6px 0;line-height:1.75}.worked .how{color:var(--teal);font-size:15px}.caution{border-left:3px solid var(--orange);padding:12px 17px;background:#fffaf5;max-width:870px}.caution strong{color:var(--orange)}.action-foot{border-top:1px solid var(--line);padding-top:23px;margin-top:35px;display:flex;justify-content:flex-end;gap:10px;flex-wrap:wrap}.practice-meta{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap;margin-bottom:18px}.progress-track{height:5px;border-radius:20px;background:#efedf8;overflow:hidden;min-width:150px;flex:1;max-width:340px}.progress-fill{background:var(--primary);height:100%}.question-header{display:flex;justify-content:space-between;color:var(--sub);font-size:14px;gap:10px;margin:7px 0 16px}.question-header strong{color:var(--primary)}.question-text{font-size:clamp(20px,2.4vw,26px);font-weight:730;line-height:1.65;color:var(--navy);margin:16px 0 26px;letter-spacing:-.035em}.math-inline mjx-container{display:inline-block!important;vertical-align:middle!important;margin:0 .05em!important}.choice-list{display:grid;gap:10px}.choice-item{border:1px solid #dfe0ea;text-align:left;padding:14px 16px;display:flex;align-items:center;gap:14px;background:#fff;border-radius:11px;min-height:58px;color:var(--ink);font-size:17px}.choice-item.selected{border:2px solid var(--primary);padding:13px 15px;background:var(--soft)}.choice-number{flex:none;width:28px;height:28px;border-radius:50%;border:1px solid #cbcbdc;display:grid;place-items:center;color:var(--sub);font-size:14px}.choice-item.selected .choice-number{background:var(--primary);border-color:var(--primary);color:#fff}.answer-input{font-size:22px;border:1px solid #d3d3df;border-radius:11px;padding:13px 16px;min-height:58px;width:min(390px,100%);background:#fff}.input-tip{font-size:12px;color:var(--sub);margin:10px 0}.keypad{display:flex;gap:7px;flex-wrap:wrap;margin:12px 0}.keypad .btn{min-width:47px;min-height:46px;padding:7px}.feedback{background:#f8fbfb;border:1px solid #cbdedb;padding:21px 23px;margin-top:23px;border-radius:11px;font-size:15px;line-height:1.77}.feedback.wrong{background:#fffaf6;border-color:#eedccb}.feedback h3{font-size:18px;color:var(--teal);margin:0 0 13px}.feedback.wrong h3{color:var(--orange)}.sol-row{padding:6px 0;border-bottom:1px solid #e3e9e8}.sol-row:last-child{border:0}.sol-row strong{display:inline-block;min-width:80px;color:var(--navy)}.sol-steps{margin:5px 0 8px 0;padding-left:20px}.sol-steps li{margin:5px 0}.sol-answer{color:var(--primary);font-weight:750}.end-unit{padding:26px 0}.end-unit h3{font-size:24px}.end-unit p{color:var(--sub)}.end-stat{display:flex;gap:12px;margin:22px 0;flex-wrap:wrap}.stat{background:var(--soft);border-radius:11px;padding:12px 18px;min-width:130px}.stat strong{display:block;font-size:26px;color:var(--primary)}.level-nav{display:flex;gap:7px;flex-wrap:wrap;margin-bottom:13px}.level-nav .btn.on{background:var(--primary);color:#fff;border-color:var(--primary)}.builder-head{margin-bottom:28px}.builder-head h2{font-size:32px;margin:7px 0}.builder{display:grid;grid-template-columns:minmax(280px,1fr) minmax(280px,1fr);gap:28px;align-items:start}.panel{border:1px solid var(--line);border-radius:13px;padding:23px}.panel h3{font-size:18px;margin-bottom:17px}.unit-opts{display:grid;grid-template-columns:1fr;gap:4px}.unit-opt{display:flex;align-items:center;gap:12px;padding:9px 8px;min-height:41px;font-size:14px}.unit-opt input,.check input{width:18px;height:18px;accent-color:var(--primary)}.field{margin-bottom:21px}.field label.field-title{font-size:14px;font-weight:720;display:block;margin-bottom:8px}.field input[type=text],.field select{width:100%;padding:11px 12px;height:47px;border:1px solid #d1d2df;border-radius:9px;background:white}.check{display:flex;align-items:center;gap:11px;margin:13px 0;font-size:14px}.build-count{font-size:13px;color:var(--teal);font-weight:700}.build-actions{margin-top:20px;display:flex;gap:10px;flex-wrap:wrap}.dialog[hidden]{display:none!important}.dialog{position:fixed;inset:0;z-index:90;background:rgba(21,22,43,.70);display:flex;flex-direction:column;align-items:center}.dialog-toolbar{width:100%;padding:12px 24px;background:#fff;display:flex;justify-content:space-between;align-items:center;gap:12px;min-height:68px;flex-wrap:wrap}.dialog-toolbar strong{color:var(--navy)}.dialog-scroll{flex:1;overflow:auto;width:100%;padding:28px 16px 60px}.preview-doc{transform-origin:top center;width:210mm;margin:0 auto;background:white;box-shadow:0 10px 55px #0004;min-height:297mm;padding:18mm 16mm;color:#111}.preview-note{text-align:center;color:#e5e5ec;font-size:12px;margin:0 0 16px}.print-only{display:none}.print-paper{color:#111;font-family:"Malgun Gothic","Apple SD Gothic Neo",sans-serif;font-size:11pt;line-height:1.52}.print-header{border-bottom:2px solid #292929;padding-bottom:4mm;margin-bottom:6mm}.print-header h1{font-size:21pt;color:#111;margin:0 0 2mm}.print-header p{font-size:10pt;margin:0 0 3mm}.print-fields{display:flex;gap:16mm;font-size:10pt}.print-q{page-break-inside:avoid;break-inside:avoid;margin-bottom:7mm}.print-q-title{font-size:11.5pt;font-weight:700;display:flex;gap:5mm;margin:0 0 2mm}.print-q .diagram{max-width:125mm;margin-left:0;min-height:0}.print-q .diagram svg{max-height:52mm}.print-choices{font-size:10.5pt;display:grid;gap:1.5mm;padding-left:6mm}.print-answer-space{border-bottom:1px solid #bbb;min-height:9mm;margin-left:6mm;width:60mm}.print-sol{border-top:1px solid #ddd;margin-bottom:4mm;padding-top:3mm;page-break-inside:avoid;break-inside:avoid;font-size:9.5pt}.print-sol strong{color:#111}.print-sol ol{margin:1mm 0 1mm 0}.answer-start{break-before:page;page-break-before:always}.answer-start h2{color:#111;border-bottom:2px solid #333;padding-bottom:4mm;font-size:19pt}.print-footer{margin-top:10mm;padding-top:4mm;border-top:1px solid #aaa;font-size:9pt;color:#555}.toast{position:fixed;bottom:23px;left:50%;transform:translateX(-50%);background:#282442;color:white;border-radius:10px;padding:10px 17px;z-index:120;display:none;max-width:90vw;text-align:center;font-size:13px}.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0,0,0,0)}
@media(min-width:1440px){.page{padding-left:50px;padding-right:50px}.top-inner{padding-left:50px;padding-right:50px}.chapter-wrap{grid-template-columns:295px minmax(0,1fr);gap:52px}}
@media(max-width:920px){.chapter-wrap{grid-template-columns:215px minmax(0,1fr);gap:22px}.sidebar{padding-right:8px}.page{padding-left:23px;padding-right:23px}.top-inner{padding-left:23px;padding-right:23px}.builder{grid-template-columns:1fr}}
@media(max-width:690px){body{font-size:15px}.page{padding:0 17px 75px}.top-inner{padding:9px 17px;min-height:60px}.brand{font-size:18px}.top-caption{display:none}.toplinks{gap:4px}.toplinks .btn{font-size:12px;min-height:39px;padding:8px 10px}.intro-wrap{margin:35px auto}.intro-heading h1{font-size:34px}.intro-heading p{font-size:16px}.select-grid{grid-template-columns:1fr;gap:25px;margin-top:29px}.grade-button{min-height:70px;font-size:21px}.start-row{align-items:stretch}.start-row .btn{width:100%}.content-head{padding:22px 0 14px}.content-head h1{font-size:28px}.chapter-wrap{display:block;margin-top:19px}.sidebar{position:static;max-height:none;border:0;padding:0;margin-bottom:22px}.side-label{display:none}.side-units{flex-direction:row;overflow-x:auto;scrollbar-width:thin;padding-bottom:8px;gap:8px}.side-unit{min-width:150px;max-width:205px;min-height:49px;flex:none;background:#fafafe;border:1px solid var(--line)}.side-unit.on{border-color:#bdb3ff}.side-footer{display:none}.chapter-heading h2{font-size:30px}.chapter-heading p{font-size:15px}.concept{font-size:16px}.concept .lead{font-size:16px}.concept h3{font-size:20px}.worked{padding-left:13px}.tabs{margin:20px 0}.question-text{font-size:20px}.preview-doc{margin-left:auto;margin-right:auto}.dialog-toolbar{padding:9px 11px}.dialog-toolbar .btn{padding:7px 10px;font-size:12px;min-height:35px}.dialog-scroll{padding:10px 7px 35px}.feedback{padding:17px 15px}.sol-row strong{min-width:67px}}
@media(max-width:380px){.toplinks .btn{font-size:11px;padding:7px 8px}.brand{font-size:17px}.grades{gap:7px}.grade-button{padding:12px 9px}.keypad .btn{min-width:42px}}
@media print{@page{size:A4 portrait;margin:13mm 15mm}html,body{margin:0!important;background:#fff!important;width:auto!important;print-color-adjust:exact;-webkit-print-color-adjust:exact}body>*:not(#printSurface){display:none!important}#printSurface{display:block!important;position:static!important;margin:0!important;padding:0!important;width:auto!important}#printSurface .print-paper{display:block!important}#printSurface .print-q .diagram svg{max-height:45mm}#printSurface .print-q{break-inside:avoid;page-break-inside:avoid}#printSurface mjx-container{max-width:100%}}