:root{--bg:#f3f1ec;--paper:#fffefa;--ink:#1d2428;--muted:#687075;--faint:#969b9d;--line:#d8d7d2;--soft:#ebe9e3;--accent:#344d5b;--accent2:#263d49;--accent-soft:#edf1f2;--ok:#51655a;--ok-soft:#f1f4f1;--danger:#765a57;--danger-soft:#f6f1f0;--sidebar:252px;--header:62px;--radius:8px;--shadow:0 8px 28px rgba(35,39,41,.035)}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--ink);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif;line-height:1.55;-webkit-font-smoothing:antialiased}button,input,select{font:inherit}button{cursor:pointer}a{text-decoration:none;color:inherit}.hidden{display:none!important}
@keyframes spin{to{transform:rotate(360deg)}}:focus-visible{outline:3px solid rgba(48,74,95,.2);outline-offset:2px}.m-app{min-height:100vh}.m-topbar{position:sticky;top:0;z-index:50;height:var(--header);background:rgba(255,255,255,.95);backdrop-filter:blur(14px);border-bottom:1px solid var(--line)}.m-topbar-inner{height:100%;max-width:1600px;margin:auto;padding:0 22px;display:grid;grid-template-columns:minmax(205px,1fr) auto auto minmax(150px,1fr);align-items:center;gap:16px}.m-brand{display:flex;align-items:center;gap:10px;min-width:0}.m-brand-mark{width:38px;height:38px;display:grid;place-items:center;border:1px solid #27313a;border-radius:9px;background:#fff;font-size:12px;font-weight:800}.m-brand-copy{display:grid}.m-brand-copy strong{font-size:14px;line-height:1.2}.m-brand-copy small{font-size:10px;color:var(--faint);margin-top:2px}.suite-tabs,.mode-tabs{display:flex;gap:3px;padding:3px;border:1px solid var(--soft);background:#f7f8f9;border-radius:9px}.suite-tabs a,.mode-tabs button{border:0;background:transparent;border-radius:6px;padding:7px 11px;color:#58636c;font-size:12px;white-space:nowrap}.suite-tabs a.active,.mode-tabs button.active{background:#fff;color:#203748;box-shadow:inset 0 0 0 1px #ccd4da,0 1px 2px rgba(20,30,40,.04);font-weight:650}.m-top-actions{justify-self:end;display:flex;gap:5px}.icon-btn{width:36px;height:36px;border:1px solid transparent;border-radius:8px;background:transparent;color:#56616a}.icon-btn:hover,.icon-btn[aria-pressed="true"]{background:var(--accent-soft);border-color:#d7e0e6;color:var(--accent)}.mobile-strip{display:none}.m-workspace{max-width:1600px;margin:auto;padding:20px 22px 58px;display:grid;grid-template-columns:var(--sidebar) minmax(0,1fr);gap:26px}.m-sidebar{position:sticky;top:calc(var(--header) + 18px);align-self:start;max-height:calc(100vh - var(--header) - 34px);overflow:auto;padding:2px 3px 20px 0;scrollbar-width:thin}.side-heading{display:flex;justify-content:space-between;align-items:flex-start}.eyebrow{font-size:9px;letter-spacing:.12em;color:var(--faint);font-weight:750}.side-heading h2{font-size:16px;margin:2px 0 12px}.mobile-close{display:none}.scope-switch{display:grid;grid-template-columns:1fr 1fr;gap:4px;padding:4px;background:#eceff1;border-radius:9px}.scope-switch button{border:0;background:transparent;padding:8px 7px;border-radius:6px;color:#65717a;font-size:12px}.scope-switch button.active{background:#fff;color:#243847;font-weight:650;box-shadow:0 1px 2px rgba(0,0,0,.04)}.filter-block{display:grid;gap:11px;padding:16px 0;border-bottom:1px solid var(--line)}.filter-count{display:flex;align-items:baseline;gap:6px;color:var(--muted);font-size:11px}.filter-count strong{font-size:22px;color:var(--ink);font-variant-numeric:tabular-nums}.field-row{display:grid;grid-template-columns:1fr 1fr;gap:8px}label{display:grid;gap:5px;color:var(--muted);font-size:10px}select,input[type=search]{width:100%;height:37px;border:1px solid var(--line);border-radius:7px;background:#fff;padding:0 9px;color:var(--ink);font-size:12px}.text-link{justify-self:start;border:0;background:transparent;color:var(--muted);font-size:11px;padding:0;text-decoration:underline;text-decoration-color:#c8ced3}.chapter-block{padding:15px 0;border-bottom:1px solid var(--line)}.section-caption{display:flex;justify-content:space-between;align-items:center;margin-bottom:8px;color:var(--muted);font-size:10px;font-weight:650}.mini{border:0;background:transparent;color:var(--muted);font-size:10px;padding:3px 6px;border-radius:5px}.mini.active{background:var(--accent-soft);color:var(--accent)}.chapter-tree{display:grid;gap:4px}.chapter-item{border-radius:8px}.chapter-row{width:100%;border:0;background:transparent;display:grid;grid-template-columns:20px minmax(0,1fr) auto;align-items:center;gap:6px;padding:8px 6px;text-align:left;border-radius:7px;color:#47545e}.chapter-row:hover{background:#eef1f3}.chapter-row.active{background:var(--accent-soft);color:var(--accent);font-weight:650}.chapter-row .chev{transition:.15s;display:inline-block;text-align:center}.chapter-item.open .chev{transform:rotate(90deg)}.chapter-count{font-size:10px;color:var(--faint);font-variant-numeric:tabular-nums}.section-list{display:none;padding:2px 0 5px 25px}.chapter-item.open .section-list{display:grid;gap:2px}.section-row{border:0;background:transparent;text-align:left;padding:7px 8px;border-radius:6px;color:#66717a;font-size:10px;display:flex;justify-content:space-between;gap:5px}.section-row:hover{background:#f0f2f3}.section-row.active{background:#edf2f5;color:#2e4c61}.section-row em{font-style:normal;color:#9aa2a8;font-size:9px}.taxonomy-note{margin:10px 5px 0;color:#959da4;font-size:9px;line-height:1.55}.side-progress{padding:15px 0}.progress-line{display:flex;justify-content:space-between;color:var(--muted);font-size:10px}.progress-line strong{color:var(--ink)}.progress-track,.index-track{height:3px;background:#e3e7ea;border-radius:99px;overflow:hidden}.progress-track{margin:8px 0 12px}.progress-track i,.index-track i{display:block;height:100%;width:0;background:var(--accent);transition:width .2s}.metrics{display:grid;grid-template-columns:repeat(4,1fr);gap:5px}.metrics div{text-align:center}.metrics b{display:block;font-size:13px}.metrics span{display:block;color:var(--faint);font-size:8px}.m-main{min-width:0}.question-view,.review-view{max-width:1160px;margin:0 auto}.question-view{background:var(--paper);border:1px solid var(--line);border-radius:14px;box-shadow:var(--shadow);overflow:hidden}.question-head{padding:22px 25px 17px;display:flex;justify-content:space-between;gap:20px}.crumbs{display:flex;flex-wrap:wrap;gap:5px}.crumbs span{font-size:9px;color:#63707a;border:1px solid var(--soft);background:#fafbfb;border-radius:5px;padding:3px 6px}.question-head h1{font-size:18px;margin:9px 0 5px;font-weight:700}.question-sub{display:flex;align-items:center;gap:8px;flex-wrap:wrap}.section-badge,.status-badge{font-size:10px;color:var(--muted)}.status-badge.wrong{color:var(--danger)}.status-badge.mastered{color:var(--ok)}.inline-link{border:0;background:transparent;padding:0;color:var(--accent);font-size:10px;text-decoration:underline;text-decoration-color:#aabac5}.head-side{display:flex;align-items:flex-start;gap:8px;color:var(--faint);font-size:11px}.star-btn{width:34px;height:34px;border:1px solid var(--soft);background:var(--paper);border-radius:8px;font-size:20px;line-height:1;color:#78838c}.star-btn.active{color:#334d60;background:var(--accent-soft)}.index-track{height:2px}.question-body{padding:26px 25px 23px}.image-panel{position:relative;border:1px solid var(--line);border-radius:8px;background:var(--paper);padding:18px;overflow:auto}.image-panel img{display:block;max-width:100%;height:auto;margin:auto;opacity:0;transition:opacity .25s ease}.image-panel img.loaded{opacity:1}.image-panel.wide img{max-width:100%}.image-panel.readable{overflow-x:auto}.image-panel.readable img{max-width:none}.panel-tools{position:absolute;right:8px;top:8px;display:flex;gap:5px;z-index:2}.panel-tools button{border:1px solid #dce1e5;border-radius:6px;background:rgba(255,255,255,.95);padding:5px 8px;color:#64717a;font-size:10px;box-shadow:0 1px 2px rgba(20,30,40,.03)}.panel-tools button[aria-pressed="true"]{background:var(--accent-soft);border-color:#c9d5dd;color:var(--accent)}.zoom-btn,.read-btn{font-weight:500}.choice-box{display:grid;grid-template-columns:repeat(4,1fr);gap:8px;margin-top:18px}.choice-box button{border:1px solid var(--line);background:var(--paper);border-radius:8px;padding:10px;display:flex;align-items:center;gap:8px;color:#53606a}.choice-box button b{width:27px;height:27px;display:grid;place-items:center;border:1px solid #ccd3d8;border-radius:50%;font-size:12px}.choice-box button:hover{border-color:#aebac2;background:#fafbfb}.choice-box button.selected{border-color:#93a8b6;background:var(--accent-soft);color:#29475a}.choice-box button.correct{border-color:#a8bdae;background:var(--ok-soft);color:var(--ok)}.choice-box button.incorrect{border-color:#cbaaaa;background:var(--danger-soft);color:var(--danger)}.work-hint{margin-top:18px;padding:11px 13px;border-left:3px solid #b7c1c8;background:#f8f9fa;color:#66717a;font-size:11px}.feedback{margin-top:12px;padding:10px 12px;border-radius:8px;font-size:11px}.feedback.ok{background:var(--ok-soft);color:var(--ok)}.feedback.bad{background:var(--danger-soft);color:var(--danger)}.feedback.neutral{background:#f1f3f4;color:#5f6c76}.action-row{display:flex;gap:8px;flex-wrap:wrap;margin-top:18px}.button{min-height:40px;border-radius:8px;padding:0 18px;border:1px solid var(--line);font-size:13px;font-weight:600}.button.primary{background:var(--accent);border-color:var(--accent);color:#fff}.button.primary:hover{background:var(--accent2)}.button.secondary{background:var(--paper);color:var(--muted)}.answer-area{border-top:1px solid var(--line);padding:22px 25px 25px;background:#fbfcfc}.answer-top{display:flex;justify-content:space-between;gap:15px;align-items:flex-start}.answer-top h2{font-size:16px;margin:2px 0 0}.answer-tabs{display:flex;padding:3px;border:1px solid var(--line);border-radius:8px;background:#f3f5f6}.answer-tabs button{border:0;background:transparent;padding:6px 10px;border-radius:5px;color:#69747d;font-size:10px}.answer-tabs button.active{background:#fff;color:#263f52;box-shadow:0 1px 2px rgba(0,0,0,.04)}.rebuild-panel{margin-top:18px}.solution-certified{display:grid;gap:14px}.solution-summary{display:grid;grid-template-columns:auto minmax(0,1fr);gap:13px;padding:15px;border:1px solid #dce4e9;border-radius:10px;background:#fff}.answer-pill{min-width:48px;min-height:48px;height:auto;display:grid;place-items:center;background:var(--accent);color:#fff;border-radius:9px;padding:8px 10px;font-size:18px;font-weight:750;line-height:1.25;text-align:center}.answer-pill-long{max-width:280px;font-size:12px;white-space:normal;overflow-wrap:anywhere}.solution-summary h3{font-size:14px;margin:0 0 3px}.solution-summary p{margin:0;color:#66717a;font-size:11px}.solution-summary .solution-result{margin-top:6px;color:#334853}.solution-result b{font-size:10px;margin-right:5px;color:#5d6a73}.solution-block{padding:14px 0;border-top:1px solid var(--soft)}.solution-block h4{font-size:11px;margin:0 0 8px;color:#46545e}.solution-block p,.solution-block li{font-size:12px;color:#35434d}.solution-block ol{margin:0;padding-left:20px;display:grid;gap:7px}.solution-key{display:grid;grid-template-columns:1fr 1fr;gap:10px}.solution-key div{padding:12px;border-radius:8px;background:#f2f5f6}.alternate-solution{border-top:1px solid var(--soft);padding-top:12px}.alternate-solution summary{cursor:pointer;color:#405563;font-size:11px;font-weight:650}.alternate-solution ol{margin:10px 0 0;padding-left:20px;display:grid;gap:6px}.alternate-solution li,.alternate-solution p{font-size:11px;color:#4b5963}.alternate-solution p{margin:8px 0 0;color:#73808a}.solution-key b{display:block;font-size:10px;color:#5c6871;margin-bottom:4px}.solution-key span{font-size:11px}.pending-solution{border:1px dashed #cfd6db;border-radius:10px;padding:18px;background:#fff}.pending-solution strong{font-size:13px}.pending-solution p{font-size:11px;color:#68747d;margin:7px 0 0}.quality-line{margin-top:10px;display:flex;gap:6px;flex-wrap:wrap}.quality-line span{font-size:9px;border:1px solid var(--soft);border-radius:5px;padding:3px 6px;color:#74808a}.official-panel{margin-top:18px}.reference-notice{display:flex;gap:8px;align-items:baseline;margin-bottom:10px}.reference-notice strong{font-size:11px}.reference-notice span{font-size:10px;color:#7a858d}.answer-image-panel{background:#fff}.self-grade{display:flex;align-items:center;gap:8px;flex-wrap:wrap;margin-top:15px;font-size:10px;color:#68747d}.self-grade button{border:1px solid var(--line);background:#fff;border-radius:7px;padding:7px 10px;color:#56636c}.question-nav{display:flex;justify-content:space-between;padding:15px 25px;border-top:1px solid var(--line);background:#fff}.question-nav button{border:0;background:transparent;color:#52616c;font-size:13px;font-weight:600;padding:10px 20px;border-radius:8px;transition:background .15s ease,transform .1s ease;cursor:pointer}.empty{max-width:800px;margin:80px auto;text-align:center}.empty-symbol{font-size:34px;color:#a4acb2}.empty h2{font-size:18px}.empty p{color:var(--muted);font-size:12px}.review-hero{border-bottom:1px solid var(--line);padding:15px 2px 20px;display:flex;justify-content:space-between;gap:30px}.review-hero h1{font-size:25px;margin:3px 0 7px}.review-hero p{max-width:700px;color:var(--muted);font-size:12px;margin:0}.review-stats{display:grid;grid-template-columns:repeat(3,94px);gap:7px}.review-stats div{padding:10px;background:#fff;border:1px solid var(--line);border-radius:9px;text-align:center}.review-stats b{display:block;font-size:18px}.review-stats span{display:block;color:var(--faint);font-size:8px}.knowledge-map{display:grid;gap:12px;padding:20px 0}.knowledge-node{background:#fff;border:1px solid var(--line);border-radius:11px;padding:16px 18px}.knowledge-node header{display:flex;justify-content:space-between;gap:16px;align-items:flex-start}.knowledge-node h3{font-size:14px;margin:0}.knowledge-node .node-id{color:var(--faint);font-size:10px;margin-right:5px}.knowledge-node p{font-size:11px;color:#59666f;margin:8px 0 0}.node-meta{font-size:9px;color:#8b959c;white-space:nowrap}.node-actions{display:flex;gap:7px;margin-top:12px}.node-actions button{border:1px solid var(--soft);background:#fafbfb;border-radius:6px;padding:6px 8px;color:#5b6871;font-size:9px}.review-bottom{display:flex;align-items:center;gap:12px;padding:4px 0 30px}.review-bottom span{font-size:10px;color:#7d878f}.dialog{width:min(1000px,calc(100vw - 36px));max-height:85vh;border:1px solid var(--line);border-radius:12px;padding:0;background:var(--paper);box-shadow:0 30px 90px rgba(15,25,34,.2);display:flex;flex-direction:column}.dialog::backdrop{background:rgba(23,31,38,.42);backdrop-filter:blur(2px)}.dialog-head{display:flex;justify-content:space-between;align-items:flex-start;padding:17px 19px;border-bottom:1px solid var(--line);flex-shrink:0}.dialog-head h2{font-size:16px;margin:2px 0}.dialog-head p{font-size:10px;color:var(--muted);margin:3px 0 0}.dialog-head>button{border:0;background:transparent;font-size:24px;color:#6c7780}.question-grid{padding:17px;display:grid;grid-template-columns:repeat(10,1fr);gap:6px;overflow:auto;flex:1;min-height:0}.qnav-group{grid-column:1/-1;margin:11px 0 2px;font-size:10px;color:#69747d}.qcell{height:36px;border:1px solid var(--line);background:#fff;border-radius:6px;color:#5c6871;font-size:10px}.qcell.current{border-color:#6f8798;background:var(--accent-soft);color:#274457}.qcell.done:after{content:"";display:block;width:4px;height:4px;border-radius:50%;background:#759080;margin:2px auto 0}.qcell.wrong:after{background:#9e6969}.image-dialog{width:min(1200px,calc(100vw - 26px));height:min(88vh,900px)}.zoom-tools{display:flex;justify-content:center;gap:5px;padding:8px;border-bottom:1px solid var(--soft)}.zoom-tools button{border:1px solid var(--line);background:#fff;border-radius:6px;min-width:36px;height:31px}.zoom-viewport{height:calc(100% - 112px);overflow:auto;background:#eef0f1;padding:28px}.zoom-viewport img{display:block;margin:auto;transform-origin:top center;max-width:none}.toast{position:fixed;left:50%;bottom:30px;transform:translate(-50%,20px);opacity:0;pointer-events:none;z-index:90;background:#26323b;color:#fff;padding:8px 12px;border-radius:7px;font-size:11px;transition:.18s}.toast.show{opacity:1;transform:translate(-50%,0)}.backdrop{display:none}.mobile-bottom{display:none}
.m-app.focus .m-workspace{grid-template-columns:1fr}.m-app.focus .m-sidebar{display:none}.m-app.focus .question-view{max-width:1300px}
@media(max-width:1100px){.m-topbar-inner{grid-template-columns:minmax(180px,1fr) auto auto}.suite-tabs{display:none}.m-workspace{grid-template-columns:225px minmax(0,1fr);gap:18px;padding-inline:16px}.choice-box{grid-template-columns:repeat(2,1fr)}}
@media(max-width:820px){:root{--header:56px}.m-topbar-inner{grid-template-columns:1fr auto;padding:0 14px}.mode-tabs{justify-self:end}.m-top-actions{display:none}.m-brand-copy small{display:none}.mobile-strip{position:sticky;top:var(--header);z-index:38;display:flex;align-items:center;gap:5px;overflow:auto;background:#fff;border-bottom:1px solid var(--line);padding:7px 12px}.mobile-strip button{border:1px solid var(--soft);background:#fff;border-radius:7px;padding:6px 9px;white-space:nowrap;color:#5d6972;font-size:10px}.mobile-strip button.active{background:var(--accent-soft);color:var(--accent)}.mobile-strip span{margin-left:auto;font-size:9px;color:var(--faint);white-space:nowrap;position:sticky;right:0;background:#fff;padding-left:8px}.m-workspace{display:block;padding:12px 12px 75px}.m-sidebar{position:fixed;z-index:70;top:0;left:0;width:min(310px,88vw);height:100dvh;max-height:none;background:#fff;padding:18px;transform:translateX(-105%);transition:.2s;box-shadow:0 20px 80px rgba(20,30,40,.18)}.m-sidebar.open{transform:translateX(0)}.mobile-close{display:block;border:0;background:transparent;font-size:24px}.backdrop{position:fixed;inset:0;z-index:65;border:0;background:rgba(20,28,34,.35)}.backdrop.show{display:block}.question-view{border-radius:10px}.question-head{padding:17px 16px 13px}.question-head h1{font-size:16px}.question-body{padding:17px 14px}.image-panel{padding:12px 8px}.answer-area{padding:17px 14px}.question-nav{display:none}.mobile-bottom{position:fixed;z-index:45;left:0;right:0;bottom:0;display:grid;grid-template-columns:58px 1fr 58px;gap:7px;padding:8px max(10px,env(safe-area-inset-right)) calc(8px + env(safe-area-inset-bottom)) max(10px,env(safe-area-inset-left));background:rgba(255,255,255,.96);border-top:1px solid var(--line);backdrop-filter:blur(12px)}.mobile-bottom button{height:42px;border:1px solid var(--line);border-radius:8px;background:#fff;color:#53616b}.mobile-bottom button:nth-child(2){background:var(--accent);color:#fff;border-color:var(--accent)}.review-hero{display:block;padding:12px 2px 16px}.review-stats{margin-top:13px;grid-template-columns:repeat(3,1fr)}.question-grid{grid-template-columns:repeat(6,1fr)}.solution-key{grid-template-columns:1fr}}
@media(max-width:520px){.solution-summary{grid-template-columns:1fr}.answer-pill{justify-self:start;max-width:100%;font-size:14px}.answer-pill-long{width:100%;justify-self:stretch;text-align:left}.m-brand-mark{width:34px;height:34px}.m-brand-copy strong{font-size:12px}.mode-tabs button{padding:6px 8px;font-size:10px}.choice-box{grid-template-columns:1fr 1fr}.choice-box button{padding:9px 8px}.choice-box button span{font-size:10px}.answer-top{display:block}.answer-tabs{margin-top:12px;width:max-content}.review-hero h1{font-size:21px}.knowledge-node{padding:14px}.knowledge-node header{display:block}.node-meta{display:block;margin-top:5px}.question-grid{grid-template-columns:repeat(5,1fr)}.zoom-viewport{padding:14px}.image-panel.readable{scrollbar-width:thin}.panel-tools button{padding:5px 7px;font-size:9px}}

/* v6 account + review logging */
.dashboard-link{display:inline-flex;align-items:center;height:36px;padding:0 11px;border:1px solid var(--line,#dfe2e6);border-radius:10px;text-decoration:none;color:inherit;font-size:12px;font-weight:750;background:#fff}.account-badge{font-size:11px;color:#73777d;max-width:110px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}.button.record{background:#24272b;color:#fff;border-color:#24272b}.review-record-dialog{width:min(660px,calc(100vw - 28px));border:0;border-radius:20px;padding:0;box-shadow:0 28px 100px rgba(0,0,0,.24)}.review-record-dialog::backdrop{background:rgba(15,17,20,.42);backdrop-filter:blur(4px)}.review-record-dialog form{padding:22px}.review-record-dialog .dialog-head{padding:0 0 18px;border-bottom:1px solid #e6e8eb}.review-record-dialog .dialog-head p{margin:4px 0 0;color:#72777e;font-size:12px}.record-grid{display:grid;grid-template-columns:1.5fr 1fr 1fr 1.4fr;gap:10px;margin-top:18px}.record-grid label,.record-wide{display:block}.record-grid label span,.record-wide span{display:block;font-size:12px;font-weight:750;margin-bottom:6px}.record-grid select,.record-grid input,.record-wide textarea{width:100%;border:1px solid #dfe2e6;border-radius:10px;background:#fff;padding:10px;font:inherit;font-size:13px;outline:none}.record-wide{margin-top:12px}.record-wide textarea{resize:vertical;line-height:1.55}.record-note{margin-top:14px;padding:10px 12px;background:#f1f3f5;border-radius:10px;color:#686d74;font-size:12px;line-height:1.55}.record-actions{display:flex;justify-content:flex-end;gap:8px;margin-top:16px}@media(max-width:760px){.dashboard-link{font-size:0;width:36px;padding:0;justify-content:center}.dashboard-link:after{content:'鈫?;font-size:15px}.account-badge{display:none}.record-grid{grid-template-columns:1fr 1fr}.review-record-dialog form{padding:16px}}

/* v9 Academic UI 鈥?quiet, publication-like, low-anxiety */
:root{
  --bg:#f3f1ec;--paper:#fffefa;--ink:#1d2428;--muted:#687075;--faint:#969b9d;
  --line:#d8d7d2;--soft:#ebe9e3;--accent:#344d5b;--accent2:#263d49;--accent-soft:#edf1f2;
  --ok:#51655a;--ok-soft:#f1f4f1;--danger:#765a57;--danger-soft:#f6f1f0;
  --radius:8px;--shadow:0 8px 28px rgba(35,39,41,.035)
}
body{background:var(--bg);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif;letter-spacing:.005em}
.m-topbar{background:rgba(250,249,246,.94);border-bottom-color:#dcdad4}
.m-topbar-inner{max-width:1540px}
.m-brand-mark{border-radius:6px;border-color:#394247;background:transparent}
.m-brand-copy strong,.side-heading h2,.question-head h1,.answer-top h2,.review-hero h1,.knowledge-node h3{
  font-family:"Songti SC","STSong","Noto Serif CJK SC","Source Han Serif SC","SimSun",serif;
  font-weight:700;letter-spacing:.015em
}
.m-brand-copy small{letter-spacing:.06em;text-transform:uppercase}
.suite-tabs,.mode-tabs{border:0;background:transparent;border-radius:0;padding:0;gap:2px}
.suite-tabs a,.mode-tabs button{border-radius:4px;padding:7px 10px}
.suite-tabs a.active,.mode-tabs button.active{background:transparent;box-shadow:none;color:var(--ink);font-weight:750;border-bottom:1px solid #536875;border-radius:0}
.dashboard-link{height:34px;border-radius:5px;background:transparent;border-color:transparent;padding-inline:8px;color:#667076;font-weight:650}
.dashboard-link:hover{border-color:var(--line);background:#faf9f6}
.icon-btn{border-radius:5px}
.m-workspace{max-width:1540px;gap:34px;padding-top:24px}
.m-sidebar{padding-right:10px}
.eyebrow{font-size:9px;letter-spacing:.14em;color:#8f9494;font-weight:650}
.scope-switch{padding:2px;background:transparent;border-bottom:1px solid var(--line);border-radius:0;gap:12px}
.scope-switch button{padding:8px 2px;border-radius:0;text-align:left}
.scope-switch button.active{background:transparent;box-shadow:none;border-bottom:1px solid var(--accent);color:var(--ink)}
.filter-block{gap:13px;padding:18px 0 20px}.filter-count strong{font-family:Georgia,"Times New Roman",serif;font-size:20px;font-weight:500}
select,input[type=search]{border-radius:5px;background:#faf9f6;border-color:#d9d7d1}
.chapter-row,.section-row{border-radius:4px}.chapter-row:hover,.section-row:hover{background:#eceae5}.chapter-row.active,.section-row.active{background:#e8ecec;color:#263d49}
.taxonomy-note{color:#999a96}
.question-view,.review-view{max-width:1080px}
.question-view{border-radius:7px;border-color:#d7d5cf;background:var(--paper);box-shadow:var(--shadow)}
.question-head{padding:24px 30px 17px}.question-head h1{font-size:20px;margin-top:11px}.crumbs span{border:0;border-bottom:1px solid #dcdad5;background:transparent;border-radius:0;padding:2px 1px;margin-right:7px}
.star-btn{border-radius:5px;background:transparent}.index-track{background:#e7e4de}.index-track i{background:#657985}
.question-body{padding:28px 30px 26px}
.image-panel{border-radius:4px;border-color:#e0ddd6;background:#fff;padding:20px;box-shadow:0 1px 0 rgba(20,20,20,.02)}
.panel-tools{right:10px;top:10px}.panel-tools button{border-radius:4px;box-shadow:none;background:rgba(255,254,250,.95)}
.choice-box button{border-radius:5px;background:#fffefa}.choice-box button b{border-radius:50%}
.work-hint{background:transparent;border-left:2px solid #aeb8bd;padding:9px 12px;color:#6c7376}
.feedback{border-radius:4px}.action-row{margin-top:20px}.button{border-radius:8px}.button.primary{background:#344d5b}.button.record{background:#2e363a;border-color:#2e363a}
.answer-area{background:#fffefa;padding:28px 30px 32px}.answer-top{padding-bottom:12px;border-bottom:1px solid #dfddd7}.answer-top h2{font-size:19px}.answer-tabs{border:0;border-radius:0;background:transparent;padding:0;gap:12px}.answer-tabs button{border-radius:0;padding:6px 1px;border-bottom:1px solid transparent}.answer-tabs button.active{box-shadow:none;background:transparent;border-bottom-color:#4b606c;color:#263c48}
.rebuild-panel{margin-top:22px}.solution-certified{gap:0}.academic-summary{display:grid;grid-template-columns:minmax(180px,.65fr) minmax(0,1.35fr);gap:34px;padding:2px 0 25px;border:0;border-radius:0;background:transparent;border-bottom:1px solid #dfddd7}
.solution-label{display:block;font-size:10px;letter-spacing:.12em;color:#8a8f90;margin-bottom:9px;font-weight:700}
.answer-pill{display:block;min-width:0;min-height:0;background:transparent;color:#20323c;border-radius:0;padding:0;font-family:Georgia,"Times New Roman","Songti SC",serif;font-size:26px;font-weight:600;text-align:left;line-height:1.45}
.answer-pill-long{max-width:none;font-size:18px;overflow-wrap:anywhere}.solution-idea h3{font-family:"Songti SC","STSong","SimSun",serif;font-size:16px;margin:0 0 7px}.solution-idea p{font-size:12px;line-height:1.8;color:#5f686d}.solution-summary .solution-result{margin-top:10px}.solution-result b{font-weight:650}
.solution-block{padding:25px 0 24px;border-top:0;border-bottom:1px solid #dfddd7}.solution-block h4{font-family:"Songti SC","STSong","SimSun",serif;font-size:16px;color:#253239;margin:0;display:inline}.solution-caption{display:inline;margin-left:7px!important;color:#929695!important;font-size:10px!important}.solution-block ol{margin-top:16px;padding-left:24px;gap:10px}.solution-block li{font-size:13px;line-height:1.9;color:#30393e}
.solution-key{grid-template-columns:1fr 1fr;gap:34px;padding:24px 0;border-bottom:1px solid #dfddd7}.solution-key div{padding:0 0 0 13px;border-radius:0;background:transparent;border-left:2px solid #b8c0c3}.solution-key b{font-family:"Songti SC","STSong","SimSun",serif;font-size:13px;color:#354248;margin-bottom:7px}.solution-key span{font-size:12px;line-height:1.75;color:#4b555a}
.alternate-solution{padding:20px 0;border-top:0;border-bottom:1px solid #dfddd7}.alternate-solution summary{font-family:"Songti SC","STSong","SimSun",serif;font-size:13px}.quality-line{margin-top:14px}.quality-line span{border:0;border-radius:0;padding:0 8px 0 0;color:#9a9d9c}.pending-solution{border-radius:4px;background:transparent}
.question-nav{background:#fffefa;padding:14px 30px}.question-nav button{font-size:11px}.knowledge-node{border-radius:5px;background:#fffefa;border-color:#dcdad4;padding:19px 20px}.knowledge-map{gap:10px}.node-actions button{border-radius:4px}
.dialog{border-radius:7px;background:#fffefa}.qcell{border-radius:4px}.zoom-viewport{background:#eeece7}.review-record-dialog{border-radius:8px}.review-record-dialog .record-grid select,.review-record-dialog .record-grid input,.review-record-dialog .record-wide textarea{border-radius:5px}.record-note{border-radius:4px;background:#f1efe9}
.focus-exit{display:none;position:fixed;z-index:120;right:18px;top:16px;border:1px solid #d4d1ca;background:rgba(255,254,250,.92);color:#596267;border-radius:5px;padding:7px 10px;font-size:11px;backdrop-filter:blur(8px)}.focus-exit.show{display:block}
.m-app.focus .m-topbar,.m-app.focus .mobile-strip{display:none}.m-app.focus .m-workspace{padding-top:18px;grid-template-columns:1fr}.m-app.focus .m-sidebar{display:none}.m-app.focus .question-view{max-width:1120px;box-shadow:none;border-color:#dedbd4}.m-app.focus .crumbs,.m-app.focus .question-sub,.m-app.focus .head-side,.m-app.focus .index-track{display:none}.m-app.focus .question-head{padding-bottom:8px}.m-app.focus .question-head h1{margin-top:0}.m-app.focus .action-row{justify-content:center}.m-app.focus .question-nav{padding-inline:18px}
@media(max-width:820px){
  .m-workspace{padding:10px 10px 66px}.question-view{border-radius:5px}.question-head{padding:18px 16px 12px}.question-body,.answer-area{padding:18px 15px 21px}.image-panel{padding:12px 8px}.academic-summary{grid-template-columns:1fr;gap:18px}.answer-pill{font-size:21px}.solution-key{grid-template-columns:1fr;gap:18px}.mobile-strip{background:rgba(250,249,246,.96)}
  .mobile-bottom{left:50%;right:auto;bottom:calc(8px + env(safe-area-inset-bottom));transform:translateX(-50%);width:min(330px,calc(100vw - 24px));grid-template-columns:44px 1fr 44px;gap:4px;padding:4px;background:rgba(250,249,246,.92);border:1px solid #d7d4cd;border-radius:8px;box-shadow:0 8px 28px rgba(30,35,38,.08);backdrop-filter:blur(14px)}
  .mobile-bottom button{height:34px;border-radius:4px;border-color:transparent;background:transparent}.mobile-bottom button:nth-child(2){background:#344d5b;border-color:#344d5b}
  .m-app.focus .mobile-bottom{display:grid}.focus-exit{right:12px;top:10px}
}
@media(max-width:520px){.answer-top{display:flex;align-items:center}.answer-tabs{margin-top:0}.answer-pill-long{font-size:16px}.solution-block li{font-size:12.5px}.m-brand-copy strong{font-family:-apple-system,BlinkMacSystemFont,"PingFang SC",sans-serif}.question-head h1{font-size:18px}}

/* v10 路 chapter closure 鈥?neutral, opt-in reflection */
.quiet-close{color:#778085!important}.quiet-close:hover{color:#41535b!important}.chapter-close-dialog{width:min(560px,calc(100vw - 28px));border-radius:6px}.chapter-close-copy{padding:4px 2px 18px;border-bottom:1px solid var(--line,#d8d5ce);margin-bottom:16px}.chapter-close-copy p{margin:0;color:#667074;line-height:1.8;font-size:13px}.chapter-close-dialog .record-actions{margin-top:0}.chapter-close-dialog .button{text-decoration:none;display:inline-flex;align-items:center;justify-content:center}


/* ===== Enterprise UX Enhances ===== */

/* Smooth question transitions */
.question-view{transition:opacity .15s ease-out}
.question-view[style*="opacity:0"]{opacity:0}

/* Answer area slide-in */
.answer-area:not(.hidden){animation:slideIn .2s ease-out}
@keyframes slideIn{from{opacity:0;transform:translateY(8px)}to{opacity:1;transform:translateY(0)}}

/* Toast improvement */
.toast{transition:opacity .25s ease,transform .25s cubic-bezier(.2,.8,.2,1);border-radius:10px;padding:10px 16px;font-size:12px;font-weight:500;box-shadow:0 8px 32px rgba(20,30,40,.18);max-width:90vw;text-align:center}
.toast.show{opacity:1;transform:translate(-50%,0)}

/* Mobile bottom bar: better touch targets + haptic feedback look */
.mobile-bottom button{transition:background .15s ease,transform .1s ease;-webkit-tap-highlight-color:transparent}
.mobile-bottom button:active{transform:scale(.92)}
.mobile-bottom button:nth-child(2){font-weight:600;letter-spacing:.02em}

/* Choice buttons: better feedback */
.choice-box button{transition:all .12s ease;-webkit-tap-highlight-color:transparent}
.choice-box button:active{transform:scale(.95)}

/* Sidebar smooth slide */
.m-sidebar{transition:transform .25s cubic-bezier(.2,.8,.2,1)}

/* Index bar smooth */
.index-track i{transition:width .3s cubic-bezier(.2,.8,.2,1)}

/* Buttons: active feedback */
.button{transition:background .15s ease,transform .1s ease;-webkit-tap-highlight-color:transparent}
.button:active{transform:scale(.97)}
.icon-btn{transition:background .12s ease;-webkit-tap-highlight-color:transparent}
.icon-btn:active{background:var(--accent-soft)}

/* Star button feedback */
.star-btn{transition:transform .15s ease,background .12s ease;-webkit-tap-highlight-color:transparent}
.star-btn:active{transform:scale(.85)}

/* Chapter row feedback */
.chapter-row,.section-row{transition:background .12s ease;-webkit-tap-highlight-color:transparent}
.chapter-row:active,.section-row:active{background:#e8eaec}

/* Loading state: better skeleton look */
#loadingState .empty-symbol{display:inline-block;font-size:28px;color:var(--accent);margin-bottom:8px}
#loadingState h2{font-size:15px;font-weight:600;color:var(--ink)}
#loadingState p{font-size:12px;color:var(--muted);margin-top:4px}

/* Hide tap delay on mobile */
button,select,a{-webkit-tap-highlight-color:transparent;-webkit-touch-callout:none}

/* Smooth scroll for question change */
html{scroll-behavior:smooth}

/* Focus mode: cleaner */
.m-app.focus .question-view{transition:max-width .25s ease,box-shadow .25s ease}

/* Dialog: better open animation */
dialog[open]{animation:dialogIn .2s ease-out}
@keyframes dialogIn{from{opacity:0;transform:translateY(10px) scale(.98)}to{opacity:1;transform:translateY(0) scale(1)}}

/* Action row buttons: better spacing on mobile */
@media(max-width:820px){
  .action-row{gap:6px}
  .action-row .button{flex:1;min-height:40px;font-size:11px;padding:0 8px}
  .question-nav{display:none}
  .mobile-bottom{padding-bottom:calc(10px + env(safe-area-inset-bottom))}
  .mobile-bottom button{min-height:46px}
}

/* ===== v10 Enterprise Polish ===== */

/* Buttons: larger, more readable, better touch targets */
.button{font-size:13px;font-weight:600;letter-spacing:.01em;padding:0 18px;min-height:40px;transition:transform .12s ease,background .15s ease,box-shadow .15s ease}
.button.primary{box-shadow:0 1px 3px rgba(52,77,91,.25)}
.button.primary:hover{background:var(--accent2);box-shadow:0 2px 8px rgba(52,77,91,.3)}
.button.primary:active{transform:scale(.97)}
.button.secondary:hover{border-color:var(--accent);color:var(--ink)}
.button.secondary:active{transform:scale(.97)}
.action-row .button{font-size:13px;min-height:42px;padding:0 12px}

/* Question nav: styled as proper buttons */
.question-nav{background:var(--paper) !important}
.question-nav button{font-size:13px;font-weight:600;padding:10px 20px;border-radius:8px;transition:background .15s ease,transform .1s ease;cursor:pointer}
.question-nav button:not(:disabled):hover{background:var(--soft);color:var(--ink)}
.question-nav button:not(:disabled):active{transform:scale(.97)}
.question-nav button:disabled{opacity:.35;cursor:not-allowed}

/* Icon buttons: clearer affordance */
.icon-btn{transition:background .15s ease,transform .1s ease}
.icon-btn:hover{background:var(--soft)}
.icon-btn:active{transform:scale(.93)}

/* Mobile bottom bar: better touch targets and warm bg */
.mobile-bottom button{background:var(--paper) !important;transition:background .15s ease,transform .1s ease}
.mobile-bottom button:not(:disabled):active{transform:scale(.95);background:var(--soft)}

/* Star/bookmark button polish */
.star-btn:hover{background:var(--soft)}
.star-btn:active{transform:scale(.9)}

/* Choice buttons: better press feedback */
.choice-box button{transition:transform .1s ease,border-color .15s ease,background .15s ease}
.choice-box button:active{transform:scale(.97)}

/* Sidebar chapter items: hover and smooth expand */
.chapter-tree .chapter-item,.chapter-tree>div{transition:background .12s ease}
.chapter-tree button:hover{color:var(--accent)}

/* Topbar links: smooth transitions */
.suite-tabs a,.mode-tabs button,.dashboard-link{transition:color .15s ease,background .15s ease}

/* Image panel: subtle inner shadow for depth */
.image-panel{box-shadow:inset 0 1px 2px rgba(0,0,0,.02)}

/* Smooth scroll for chapter tree and dialogs */
.chapter-tree{scrollbar-width:thin;scrollbar-color:var(--line) transparent}
.chapter-tree::-webkit-scrollbar{width:5px}
.chapter-tree::-webkit-scrollbar-thumb{background:var(--line);border-radius:3px}

/* Dialog backdrop: subtle blur for premium feel */
dialog{backdrop-filter:blur(2px);-webkit-backdrop-filter:blur(2px)}

/* Focus visible: keyboard accessibility */
.button:focus-visible,.icon-btn:focus-visible,.star-btn:focus-visible,.choice-box button:focus-visible,.question-nav button:focus-visible{outline:2px solid var(--accent);outline-offset:2px}

/* Loading spinner: smooth */
@keyframes spin{to{transform:rotate(360deg)}}

/* Toast: slide-up with bounce */
.toast.show{transition:opacity .25s ease,transform .35s cubic-bezier(.2,.8,.2,1.2)}

/* Badge transitions */
.account-badge{transition:opacity .2s ease}
.account-badge.guest{opacity:.85}

/* Keyboard shortcuts dialog */
.shortcuts-dialog{width:min(420px,calc(100vw - 28px))}
.shortcuts-grid{padding:18px 19px;display:grid;gap:14px;overflow:auto}
.shortcut-item{display:flex;align-items:center;gap:10px;font-size:13px;color:var(--ink)}
.shortcut-item span{color:var(--muted)}
kbd{display:inline-flex;align-items:center;justify-content:center;min-width:28px;height:28px;padding:0 6px;border:1px solid var(--line);border-radius:5px;background:var(--bg);font-size:11px;font-weight:600;color:var(--ink);font-family:inherit;box-shadow:0 1px 0 var(--line)}
.shortcut-item kbd+kbd{margin-left:-4px}