:root{color-scheme:light;--ink:#29463e;--green:#3c7965;--line:#d4e0d9;--paper:#fffefa;--gold:#97712f;font-family:"Yu Gothic","Hiragino Kaku Gothic ProN",system-ui,sans-serif;color:var(--ink);background:#f4f6f1;font-size:17px;line-height:1.85}
*{box-sizing:border-box}body{margin:0}button,input,textarea{font:inherit}button,a,input,summary,textarea{-webkit-tap-highlight-color:transparent}a{color:var(--green);text-underline-offset:4px}button,summary{cursor:pointer}[hidden]{display:none!important}:focus-visible{outline:3px solid #aa813a;outline-offset:4px}h1,h2,p{margin:0}h1,h2{font-family:"Yu Mincho","Hiragino Mincho ProN",serif;font-weight:600;line-height:1.5}.shell{max-width:1010px;margin:auto;padding:18px 24px 30px}.site-nav{display:flex;justify-content:center;gap:10px;margin:0 0 28px}.site-nav a,.button{min-height:44px;padding:7px 18px;border:1px solid #b8cdc1;border-radius:10px;background:var(--paper);text-decoration:none;display:inline-flex;align-items:center;justify-content:center;gap:8px;font-weight:500;color:var(--green);line-height:1.5}.site-nav a{font-size:14px}.button:hover{background:#ecf2eb}.primary{background:var(--green);border-color:var(--green);color:#fff}.primary:hover{background:#315f50}.page-head{border-bottom:1px solid var(--line);padding:0 6px 25px}.eyebrow{font-size:13px;letter-spacing:.13em;color:var(--green)}h1{font-size:36px;margin:4px 0}.lead{font-size:21px;margin-bottom:5px}.downloads{display:flex;flex-wrap:wrap;gap:10px;margin:18px 0 8px}.small{font-size:13px;color:#597067;line-height:1.7}.record-panel{margin:22px 0;padding:18px 20px;border:1px solid var(--line);border-radius:14px;background:var(--paper)}#practice-progress{font-size:17px;font-weight:600}.question-links{display:flex;flex-wrap:wrap;gap:8px;margin:10px 0}.question-links a{padding:4px 12px;border:1px solid var(--line);border-radius:8px;text-decoration:none;font-size:14px;min-height:38px}.question-links a[data-state="done"]{background:#eaf3e9;border-color:#88ab96}.question-links a[data-state="retry"]{border-color:#bca26b;background:#fff8e7}.record-actions{display:flex;flex-wrap:wrap;gap:18px;font-size:14px;margin-bottom:8px}.entry-help{font-size:14px;margin:22px 4px}.question{scroll-margin-top:20px;background:var(--paper);border:1px solid var(--line);border-radius:18px;padding:28px 30px;margin:0 0 28px;box-shadow:0 5px 22px #28473705}.question-head{display:flex;align-items:center;gap:18px;margin-bottom:20px}.question-number{font-family:Georgia,serif;font-size:37px;line-height:1;color:var(--green);font-weight:400}.question-level{font-size:14px;color:var(--gold)}.question-level span{font-size:12px;letter-spacing:2px;margin-left:6px}h2{font-size:23px}.prompt{font-size:18px;line-height:1.95}.ask{margin-top:9px;font-weight:500}.memo-label{display:block;font-size:14px;color:#597067;margin:20px 0 5px}.memo{width:100%;border:1px solid #c6d8cd;background:#fff;border-radius:9px;padding:12px;resize:vertical;min-height:105px;font-size:17px;line-height:1.65}.answer-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(180px,1fr));gap:16px;margin:20px 0 14px}.answer-field label{font-size:15px;display:block;margin-bottom:6px}.answer-input{display:flex;align-items:center;gap:9px}.answer-input input{width:100%;min-width:0;max-width:185px;font-size:22px;border:1px solid #b2c7bb;border-radius:8px;background:#fff;padding:8px 12px;min-height:48px}.answer-field[data-state="right"] input{border-color:#558d68;background:#f1f8ef}.answer-field[data-state="retry"] input{border-color:#a67e38;background:#fffcf1}.field-hint{font-size:13px;color:#806232;min-height:22px;display:block}.answer-field[data-state="right"] .field-hint{color:var(--green)}.actions{display:flex;gap:10px;align-items:center;flex-wrap:wrap}.earned-medal{font-size:14px;font-weight:600;color:#826120;background:linear-gradient(125deg,#fff9dcbb,#e7c56d66);border:1px solid #b8964c66;border-radius:50px;padding:6px 15px}.check-feedback{font-size:15px;min-height:28px;margin-top:10px;color:#806232}.check-feedback[data-state="right"]{color:var(--green)}details{border-top:1px solid var(--line);padding:12px 0 0;margin-top:14px}summary{min-height:40px;line-height:1.8;font-size:16px;color:var(--green);padding:4px 0}details>p{margin:12px 0;font-size:16px}.next-hint{font-size:14px}.solution-body{padding:10px 0 5px}.answer-summary{padding:12px 15px;background:#edf4e9;border-radius:10px;color:var(--green);font-size:17px;font-weight:600}.solution figure{margin:18px 0 22px;padding:15px 12px;background:#fff;border:1px solid var(--line);border-radius:12px}.line-diagram{display:block;width:100%;max-width:760px;height:auto;margin:auto;font-family:"Yu Gothic","Hiragino Kaku Gothic ProN",system-ui,sans-serif}.solution figcaption{font-size:13px;line-height:1.7;color:#597067;margin-top:8px;text-align:center}.explanation-steps{padding-left:26px;margin:10px 0 18px}.explanation-steps li{margin:12px 0;padding-left:4px}.explanation-steps li::marker{color:var(--gold)}.explanation-steps strong{display:block;font-size:18px;font-weight:500;overflow-wrap:anywhere}.explanation-steps span{display:block;font-size:15px;color:#526d61}.proof{font-size:15px;line-height:1.9;border-left:3px solid #b4cbb8;padding:5px 14px;margin-top:16px}footer{text-align:center;font-size:13px;color:#597067;padding:5px 0 15px}.skip{position:absolute;left:12px;top:-100px;background:#fff;padding:8px 14px;z-index:2}.skip:focus{top:12px}noscript{padding:20px}
.diagram-mobile{display:none}
@media(max-width:620px){:root{font-size:16px}.shell{padding:14px 14px 24px}.site-nav{margin-bottom:20px}.page-head{padding:0 2px 20px}h1{font-size:30px}.lead{font-size:19px}.downloads{gap:8px}.downloads .button{font-size:14px;flex:1 1 180px}.question{padding:21px 17px;border-radius:14px}.question-head{gap:12px;align-items:flex-start}.question-number{font-size:32px;margin-top:8px}h2{font-size:21px}.prompt{font-size:17px}.answer-grid{grid-template-columns:1fr;gap:10px}.answer-input input{max-width:220px}.solution figure{padding:15px 12px}.line-diagram{display:none}.diagram-mobile{display:block}.diagram-mobile>p{font-size:15px;color:var(--green);line-height:1.8}.diagram-person,.transfer-person{margin:15px 0 25px;color:var(--person)}.diagram-row-head{display:flex;justify-content:space-between;gap:12px;font-size:15px;margin-bottom:28px}.diagram-line{display:flex;height:12px;min-width:0;position:relative}.diagram-piece{position:relative;border-left:2px solid var(--person);height:12px;flex-shrink:0}.diagram-piece:last-child{border-right:2px solid var(--person)}.diagram-piece::after{content:"";position:absolute;left:0;right:0;top:5px;border-top:2px solid var(--person)}.diagram-piece>span{position:absolute;left:50%;bottom:10px;transform:translateX(-50%);font-size:14px;white-space:nowrap;line-height:1.7}.diagram-piece.extra{--person:var(--gold);color:var(--gold)}.diagram-note{font-size:14px!important}.solution figcaption{text-align:left;padding:0 7px}.record-panel{padding:16px}.question-links{gap:6px}.question-links a{font-size:13px;padding:6px 10px}.explanation-steps strong{font-size:17px}}
@media print{@page{size:A4;margin:14mm}.site-nav,.record-panel,.downloads,.entry-help,.actions,.check-feedback,.field-hint,.practice-hints,.solution,.memo-label,.skip,footer,.small{display:none!important}:root{background:#fff;font-size:11pt}.shell{max-width:none;padding:0}.page-head{padding:0 0 7mm}.page-head h1{font-size:19pt}.page-head .lead{font-size:11pt}.page-head>p:not(.lead){display:none}.question{border:0;border-radius:0;box-shadow:none;margin:0;padding:7mm 0;break-inside:avoid;min-height:118mm;border-bottom:1px solid #aaa}.question:nth-of-type(2n){break-after:page}.question-head{margin-bottom:4mm}h2{font-size:13pt}.question-number{font-size:22pt}.prompt{font-size:11pt;line-height:1.7}.memo{min-height:27mm;border:0;resize:none;padding:2mm 0;font-size:11pt}.memo::placeholder{color:transparent}.answer-grid{display:flex;margin:0;gap:8mm}.answer-field{flex:1}.answer-field label{font-size:9pt}.answer-input input{border:0;border-bottom:1px solid #555;border-radius:0;min-height:7mm;padding:0;font-size:11pt;background:transparent!important}.answer-input span{font-size:10pt}}

.transfer-return{border-top:1px dashed var(--line);padding-top:14px}.transfer-return>p{font-size:15px;line-height:1.8;color:var(--green)}

.math-token{white-space:nowrap}.question-footer{display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap;border-top:1px solid var(--line);margin-top:20px;padding-top:16px}.question-footer a{font-size:14px;min-height:44px;display:inline-flex;align-items:center;text-decoration:none}.question-footer .related-model{border:1px solid #b9cfc1;border-radius:10px;padding:7px 13px;background:#f1f6ed}.question-footer a:hover{text-decoration:underline}.practice-finish{border:1px solid var(--line);background:var(--paper);border-radius:16px;padding:24px 28px;margin-bottom:26px}.practice-finish p{font-size:15px}.practice-finish h2{font-size:22px}.explanation-steps strong{line-height:1.9}
@media(max-width:620px){.question-footer{gap:6px}.question-footer .related-model{order:-1;width:100%;justify-content:center;margin-bottom:6px}.practice-finish{padding:20px 17px}.question-footer a{font-size:14px}.practice-finish p{line-height:2}}
@media print{.question-footer,.practice-finish{display:none!important}}
