:root{--bg:#f5f6fa;--ink:#172b38;--muted:#637380;--line:#e0e6eb;--teal:#087e83;--teal-light:#e5f5f2;--amber:#d78726;--red:#c85353;--blue:#477ec2;--shadow:0 10px 35px #223b4910}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font-family:"Segoe UI","Microsoft YaHei",sans-serif}button,select{font:inherit}button{cursor:pointer;border:0;transition:background .18s,box-shadow .18s}button:focus-visible,a:focus-visible,select:focus-visible{outline:3px solid #cf923e;outline-offset:4px}button:disabled{cursor:default;opacity:.4}[hidden]{display:none!important}.topbar{height:76px;background:#fff;border-bottom:1px solid var(--line);padding:0 4vw;display:flex;justify-content:space-between;align-items:center}.brand{display:flex;align-items:center;gap:12px;text-decoration:none;color:var(--ink);font-size:20px;font-weight:700}.brand-icon{display:grid;place-items:center;background:var(--teal);color:white;width:38px;height:38px;border-radius:10px;font-size:26px}.brand-sub{font-weight:400;font-size:14px;margin-left:18px;color:var(--muted);border-left:1px solid var(--line);padding-left:18px}.top-actions{display:flex;align-items:center;gap:12px}.course{color:var(--muted);font-size:13px;margin-right:15px}main{max-width:1600px;margin:auto;padding:30px 4vw 116px}.heading{display:flex;justify-content:space-between;align-items:center;margin-bottom:22px}.eyebrow{color:var(--teal);font-size:12px;font-weight:700;letter-spacing:2px;margin-bottom:9px}h1{font-size:clamp(26px,2.5vw,38px);margin:0 0 8px;letter-spacing:-1px}.heading p{color:var(--muted);font-size:16px;margin:0}.chapter-number{font-size:48px;letter-spacing:-3px;color:#cbd7dd;font-weight:300}.chapter-number small{font-size:18px;letter-spacing:0}.workspace{display:grid;grid-template-columns:minmax(0,1fr) 280px;gap:22px;align-items:stretch}.visual-panel{background:#fff;box-shadow:var(--shadow);border:1px solid var(--line);border-radius:18px;overflow:hidden;min-width:0}.panel-top{display:flex;justify-content:space-between;gap:10px;padding:18px 22px;border-bottom:1px solid #edf0f3;font-size:13px;color:var(--muted)}.status{color:var(--teal);font-size:12px}.status:before{content:"";display:inline-block;width:6px;height:6px;border-radius:50%;background:currentColor;margin-right:7px}#stage{aspect-ratio:940/420;background-image:radial-gradient(#d9e2e7 1px,transparent 1px);background-size:22px 22px;overflow:hidden}#stage svg{display:block;width:100%;height:100%;font-family:inherit}.caption{min-height:60px;padding:17px 24px;background:#f5faf9;border-top:1px solid #e2eeeb;font-size:17px;line-height:1.6}.notes{padding:23px 22px;background:#edf1f4;border-radius:18px;display:flex;flex-direction:column}.note-label{font-size:11px;letter-spacing:2px;color:var(--muted);margin-bottom:16px}.notes h2{font-size:24px;line-height:1.45;margin:0 0 14px}.notes p{font-size:16px;line-height:1.8;margin:0 0 20px;color:#4b606c}.question{font-size:15px;line-height:1.8;border-top:1px solid #d4dfe5;padding-top:17px}.question:before{content:"问一问";display:block;color:var(--teal);font-size:12px;font-weight:700;margin-bottom:5px}.takeaway{padding:12px 0 0;color:var(--teal);font-size:14px;line-height:1.8}.source{font-size:11px;color:#7d8d97;margin-top:auto;padding-top:24px;line-height:1.6}.timeline{display:flex;align-items:center;gap:16px;margin-top:21px;color:var(--muted);font-size:12px}.step-dots{display:flex;gap:6px}.step-dots i{height:5px;width:26px;background:#dce4e8;border-radius:4px}.step-dots i.done{background:var(--teal)}#nextHint{margin-left:auto}.controls{position:fixed;bottom:0;left:0;right:0;background:#ffffffed;backdrop-filter:blur(16px);border-top:1px solid var(--line);height:85px;display:flex;align-items:center;justify-content:space-between;padding:0 4vw;z-index:5;gap:15px}.control-left,.control-right{display:flex;gap:12px;align-items:center}.primary{padding:15px 28px;min-width:174px;border-radius:10px;background:var(--teal);color:#fff;display:flex;align-items:center;justify-content:space-between;gap:24px;font-weight:600;box-shadow:0 4px 10px #087e8320}.primary:hover:not(:disabled){background:#05686c}.secondary{padding:12px 17px;border:1px solid #dbe3e8;border-radius:9px;background:white;color:var(--ink)}.secondary:hover:not(:disabled),.quiet:hover:not(:disabled){background:#edf4f4}.quiet{background:transparent;color:var(--muted);padding:10px 12px;border-radius:8px;font-size:13px}.keyboard-hint{font-size:12px;color:#82919c}kbd{font-family:inherit;border:1px solid #d8e0e5;border-bottom-width:2px;border-radius:4px;padding:2px 5px;background:white}.snapshots{display:grid;grid-template-columns:repeat(8,1fr);gap:6px;padding:10px 12px;background:#fafcfc}.snapshot{background:#fff;border:1px solid var(--line);border-radius:7px;padding:5px;min-width:0}.snapshot svg{width:100%;height:58px}.snapshot span{font-size:10px;color:var(--muted)}dialog{border:1px solid var(--line);border-radius:20px;padding:28px;width:min(560px,94vw);max-height:85vh;color:var(--ink);box-shadow:0 24px 80px #172b3830}dialog::backdrop{background:#142b3d65;backdrop-filter:blur(4px)}.dialog-heading{display:flex;align-items:center;justify-content:space-between}.dialog-heading h2{margin:0;font-size:24px}.muted{color:var(--muted);font-size:14px;line-height:1.8}nav{display:grid;gap:6px;margin:20px 0}nav button{text-align:left;padding:13px;border-radius:9px;background:#f3f6f8;display:flex;gap:16px;align-items:center}nav button.active{background:var(--teal-light);color:var(--teal)}nav button small{margin-left:auto;color:var(--muted)}.settings{display:flex;justify-content:space-between;align-items:center;padding:16px 0;border-top:1px solid var(--line)}select{padding:6px 10px;border:1px solid var(--line);border-radius:7px;background:white}details{font-size:12px;color:var(--muted);line-height:1.9}summary{cursor:pointer}a{color:var(--teal)}.backup{font-size:12px;background:white;border:1px solid var(--line);border-radius:7px;padding:6px 9px;margin:6px 5px 0 0;color:var(--teal)}
@media(min-width:1001px){main{height:calc(100dvh - 161px);display:flex;flex-direction:column;padding-bottom:18px}.heading,.timeline{flex-shrink:0}.workspace{flex:1;min-height:0}.visual-panel{display:flex;flex-direction:column}.panel-top,.caption,.snapshots{flex-shrink:0}#stage{flex:1;min-height:0;aspect-ratio:auto}.notes{overflow:auto}}
@media(min-width:1500px){.workspace{grid-template-columns:minmax(0,1fr) 310px}.notes h2{font-size:28px}.notes p{font-size:18px}}
@media(max-height:820px) and (min-width:1001px){main{height:calc(100dvh - 136px);padding-top:18px}.heading{margin-bottom:15px}.topbar{height:62px}.notes{padding:18px}.notes h2{font-size:22px;margin-bottom:10px}.notes p{font-size:15px;margin-bottom:12px}.note-label{margin-bottom:10px}.source{padding-top:12px}.caption{font-size:16px;min-height:52px;padding:12px 20px}.controls{height:74px}.timeline{margin-top:14px}.snapshot svg{height:44px}.snapshots{padding:6px 10px}}
@media(max-width:1000px){.workspace{grid-template-columns:1fr}.notes{display:grid;grid-template-columns:1fr 1fr;gap:12px}.note-label,.source{grid-column:1/-1;margin:0;padding:0}.notes h2{font-size:21px;margin:0}.notes p{margin:0}.question{border:0;padding:0}.course,.keyboard-hint{display:none}.heading p{font-size:14px}.topbar{padding:0 4vw}main{padding-top:22px}.snapshots{grid-template-columns:repeat(4,1fr)}}
@media(max-width:600px){.brand-sub,#fullButton,.chapter-number{display:none}.topbar{height:64px}.brand{font-size:17px}.workspace{gap:12px}.panel-top{padding:12px;font-size:11px}.caption{padding:12px;font-size:14px}.notes{display:block;padding:18px}.notes h2{margin:12px 0}.notes p,.question{font-size:14px}.source{margin-top:14px}.controls{padding:0 12px;height:76px}.primary{min-width:125px;padding:13px 16px}.secondary{padding:10px;font-size:12px}.control-left,.control-right{gap:4px}#replayButton{font-size:11px;padding:8px}.timeline{gap:8px}#nextHint{display:none}.step-dots i{width:18px}.top-actions{gap:0}}
@media(prefers-reduced-motion:reduce){button{transition:none}}

/* 试卷原题保持独立、醒目；动画与解析放在其下方。 */
.exam-panel{background:#fff;border:1px solid #bddbd8;border-left:5px solid var(--teal);border-radius:12px;margin-bottom:14px;flex-shrink:0;overflow:hidden;box-shadow:0 4px 18px #173c3a08}.exam-top{display:flex;align-items:center;gap:16px;padding:6px 16px;background:#edf7f5;min-height:34px}.exam-top strong{font-size:14px;color:var(--teal);white-space:nowrap}.exam-top #examSource{font-size:13px;color:#314a56;font-weight:600}.exam-top .quiet{margin-left:auto;padding:3px 6px;white-space:nowrap}.question-image-button{display:block;width:100%;height:142px;background:white;padding:7px 18px;cursor:zoom-in}.question-image-button img{display:block;width:100%;height:100%;object-fit:contain}.exam-panel[data-question="1"] .question-image-button{height:82px}.exam-panel[data-question="2"] .question-image-button{height:62px}.wide-dialog{width:min(1280px,94vw)}#largeQuestion{display:block;max-width:100%;max-height:68vh;margin:25px auto 12px;object-fit:contain}.large-source{font-size:17px;text-align:right;font-weight:600}#snapshotGallery{display:grid;grid-template-columns:repeat(4,1fr);gap:16px;margin-top:24px}#snapshotGallery .snapshot{padding:12px}#snapshotGallery .snapshot span{font-size:15px}#snapshotGallery svg{height:170px}#hanoiTools{margin-left:auto;display:flex;gap:8px;align-items:center;font-size:12px}#diskCount{padding:3px 8px}.panel-top{align-items:center}#snapshotButton{padding:0 8px;color:var(--teal)}.notes .source{padding-top:12px}.notes h2{font-size:22px}.notes p{font-size:15px;line-height:1.65}.question,.takeaway{font-size:14px;line-height:1.7}
@media(min-width:1001px){.topbar{height:58px}main{height:calc(100dvh - 143px);padding-top:16px;padding-bottom:12px}.heading{margin-bottom:13px}.eyebrow{margin-bottom:5px;font-size:10px}h1{font-size:30px;margin-bottom:5px}.heading p{font-size:14px}.chapter-number{font-size:37px}.panel-top{padding:11px 18px}.timeline{margin-top:10px}.notes{padding:17px}.note-label{margin-bottom:10px}.notes p{margin-bottom:12px}.question{padding-top:12px}.source{font-size:10px}}
@media(max-height:820px) and (min-width:1001px){.topbar{height:52px}main{height:calc(100dvh - 126px);padding-top:12px;padding-bottom:10px}.heading{margin-bottom:10px}.eyebrow{display:none}h1{font-size:27px}.heading p{font-size:13px}.exam-panel{margin-bottom:10px}.question-image-button{height:122px;padding:5px 12px}.exam-panel[data-question="1"] .question-image-button{height:70px}.exam-panel[data-question="2"] .question-image-button{height:53px}.exam-top{padding:4px 12px;min-height:29px}.exam-top #examSource{font-size:12px}.notes h2{font-size:20px}.notes p{font-size:14px}.caption{min-height:45px;padding:9px 16px;font-size:14px}.timeline{margin-top:9px}.panel-top{padding:9px 16px}}
@media(max-width:1000px){.exam-top{flex-wrap:wrap;gap:6px}.exam-top #examSource{order:3;width:100%;font-size:12px}.question-image-button{height:auto;max-height:none;padding:12px}.question-image-button img{height:auto}.exam-panel[data-question] .question-image-button{height:auto}#stage:has(svg[viewBox="0 0 940 340"]){aspect-ratio:940/340}#snapshotGallery{grid-template-columns:repeat(2,1fr)}#snapshotGallery svg{height:130px}}
.question-nav-button{position:fixed;left:0;top:42%;z-index:8;display:flex;flex-direction:column;align-items:center;gap:10px;width:38px;padding:15px 8px;background:var(--teal);color:#fff;border-radius:0 10px 10px 0;box-shadow:0 3px 12px #087e8328;font-size:15px}.question-nav-button span:last-child{writing-mode:vertical-rl;letter-spacing:3px}.question-nav-button:hover{background:#05686c}.question-drawer{position:fixed;inset:0 auto 0 0;margin:0;width:min(440px,92vw);height:100dvh;max-height:100dvh;border-radius:0 18px 18px 0;padding:26px 22px}.question-drawer nav{gap:8px}.question-drawer nav h3{font-size:12px;letter-spacing:2px;color:var(--muted);margin:12px 0 3px}.question-drawer nav button{display:block;padding:14px;text-align:left;line-height:1.5}.question-drawer nav strong{display:block;font-size:16px}.question-drawer nav small{display:block;margin:6px 0 0;font-size:11px;font-weight:400;line-height:1.7}.question-drawer nav button[aria-current="page"]{box-shadow:inset 3px 0 var(--teal)}
@media(max-width:1000px){main{padding-left:46px}.question-nav-button{width:31px;font-size:13px;padding:12px 6px}}

/* Entry cover */
.cover{min-height:100vh;min-height:100svh;display:grid;place-items:center;padding:64px 24px;background:radial-gradient(ellipse at 50% 15%,#e5f5f2 0,transparent 65%),var(--bg)}
.cover-content{width:100%;max-width:1120px;text-align:center}
.cover-kicker{margin:0 0 26px;color:var(--teal);font-size:15px;letter-spacing:2px}
.cover h1{font-size:clamp(32px,4.4vw,60px);line-height:1.45;letter-spacing:-1px;margin:0;text-wrap:balance}
.cover-references{margin:36px auto 0;max-width:780px}
.cover-references h2{font-size:14px;font-weight:500;color:var(--muted);margin:0 0 16px}
.cover-references nav{display:flex;flex-wrap:wrap;justify-content:center;gap:12px 24px;font-size:14px;line-height:1.8}
.cover-references a{color:var(--teal);text-underline-offset:5px;text-decoration-color:#087e8350}
.cover-references a:hover{text-decoration-color:var(--teal)}
.cover-start{margin:44px auto 0}
@media(max-width:600px){.cover{padding:44px 24px}.cover-kicker{font-size:12px}.cover-references nav{flex-direction:column;gap:12px}.cover-start{margin-top:32px}}