:root{--ink:#18302e;--muted:#6f8581;--line:#dce8e4;--paper:#f4f8f6;--card:#fff;--deep:#142b2c;--deep-2:#1e3b39;--mint:#169681;--mint-soft:#e5f5ef;--amber:#c08331;--red:#d05c54;--blue:#4a78b5;--shadow:0 12px 32px rgba(18,55,48,.09)}
*{box-sizing:border-box}html,body{margin:0;min-width:320px;background:var(--paper);color:var(--ink);font-family:Inter,"Noto Sans SC","Microsoft YaHei",sans-serif}button,input,select,textarea{font:inherit}button{cursor:pointer}.is-hidden{display:none!important}.app-shell{min-height:100vh;display:grid;grid-template-columns:246px minmax(0,1fr)}
.sidebar{display:flex;flex-direction:column;min-height:100vh;padding:25px 15px 18px;background:var(--deep);color:#dbe9e5;position:sticky;top:0;height:100vh;align-self:start;overflow-y:auto;overscroll-behavior:contain}.brand{display:flex;align-items:center;gap:11px;padding:0 10px 23px}.brand-mark{display:grid;place-items:center;width:36px;height:36px;border-radius:9px;background:#d9f1e9;color:var(--mint);font:bold 12px ui-monospace,monospace}.brand strong{display:block;color:#fff;font-size:15px}.brand small{display:block;margin-top:3px;color:#9bb9b1;font-size:10px}.source-badge{display:flex;align-items:center;gap:8px;padding:9px 10px;border:1px solid rgba(222,244,237,.16);border-radius:6px;color:#a5c2bb;font-size:11px}.source-badge span{width:7px;height:7px;border-radius:50%;background:#59d0b4;box-shadow:0 0 0 3px rgba(89,208,180,.13)}.primary-nav{display:grid;gap:4px;margin-top:24px}.nav-item,.category-item{display:flex;align-items:center;width:100%;border:0;border-radius:6px;background:transparent;color:#9ab5af;text-align:left}.nav-item{justify-content:space-between;padding:11px 10px;font-size:12px}.nav-item:hover,.nav-item.is-active{background:var(--deep-2);color:#fff}.nav-item.is-active{box-shadow:inset 3px 0 var(--mint)}.nav-item b,.category-item b{color:#6f9790;font:10px ui-monospace,monospace}.sidebar-heading{margin:29px 10px 9px;color:#739790;font:10px ui-monospace,monospace;letter-spacing:1px}.category-list{display:grid;gap:2px}.category-item{justify-content:space-between;padding:8px 10px;font-size:11px}.category-item:hover,.category-item.is-active{background:rgba(255,255,255,.08);color:#fff}.category-item.is-active{box-shadow:inset 2px 0 var(--mint)}.sidebar-bottom{margin-top:auto;padding:16px 10px 0;border-top:1px solid rgba(222,244,237,.13)}.sidebar-bottom a{display:block;margin-top:7px;color:#9bb9b1;text-decoration:none;font-size:10px}.sidebar-bottom a:hover{color:#fff}
.main-content{min-width:0}.topbar{position:sticky;top:0;z-index:5;display:flex;align-items:center;justify-content:space-between;height:66px;padding:0 42px;border-bottom:1px solid var(--line);background:rgba(255,255,255,.9);backdrop-filter:blur(12px)}.breadcrumb{display:flex;align-items:center;gap:9px;color:#9aaea9;font-size:11px}.breadcrumb i{font-style:normal;color:#c3d0cd}.breadcrumb strong{color:var(--ink)}.top-actions{display:flex;align-items:center;gap:9px}.search-box{display:flex;align-items:center;gap:7px;width:min(360px,38vw);height:36px;padding:0 10px;border:1px solid var(--line);border-radius:6px;background:#fff;color:#78938e}.search-box>span{font-size:21px;line-height:1}.search-box input{width:100%;min-width:0;border:0;outline:0;background:transparent;color:var(--ink);font-size:11px}.search-box kbd{padding:2px 5px;border:1px solid var(--line);border-radius:3px;color:#9aaca8;font:10px ui-monospace,monospace}.icon-button{display:grid;place-items:center;width:35px;height:35px;border:1px solid var(--line);border-radius:6px;background:#fff;color:#527873}.icon-button:hover{border-color:#9bd2c6;color:var(--mint)}.menu-toggle{display:none}
.view{max-width:1320px;margin:0 auto;padding:39px 48px 60px}.hero-row{display:flex;align-items:flex-end;justify-content:space-between;gap:26px;margin-bottom:27px}.eyebrow{margin:0 0 8px;color:#71928b;font:10px ui-monospace,monospace;letter-spacing:1.1px}.hero-row h1{margin:0;font-size:clamp(28px,3.2vw,42px);line-height:1.2}.intro{max-width:620px;margin:10px 0 0;color:var(--muted);font-size:12px;line-height:1.7}.metric{min-width:110px;padding:0 0 3px 18px;border-left:1px solid var(--line)}.metric strong{display:block;color:var(--mint);font-size:26px;line-height:1.1}.metric span{color:#829a94;font-size:10px}.topic-scroller{display:flex;flex-wrap:wrap;gap:7px;margin-bottom:19px}.topic-chip{padding:8px 11px;border:1px solid #d2e3de;border-radius:6px;background:transparent;color:#6e8983;font-size:10px;white-space:nowrap}.topic-chip:hover,.topic-chip.is-active{border-color:#96d1c3;background:var(--mint-soft);color:var(--mint)}.toolbar{display:flex;align-items:center;justify-content:space-between;min-height:45px;padding:10px 2px;border-top:1px solid var(--line);border-bottom:1px solid var(--line);color:#839691;font-size:10px}.toolbar-controls{display:flex;gap:17px}.toolbar label{display:flex;align-items:center;gap:5px;white-space:nowrap}.toolbar select{border:0;outline:0;background:transparent;color:var(--ink);font-size:10px}.browse-grid{display:grid;grid-template-columns:minmax(0,1.08fr) minmax(350px,.92fr);align-items:start;gap:16px;margin-top:16px}.question-list{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px;min-width:0}.question-card{position:relative;display:flex;flex-direction:column;min-width:0;aspect-ratio:1/.86;padding:15px;border:1px solid var(--line);border-top:3px solid var(--line);border-radius:7px;background:var(--card);cursor:pointer;transition:border-color .18s,box-shadow .18s,transform .18s}.question-card:hover,.question-card.is-selected{border-color:#9bd2c5;box-shadow:var(--shadow);transform:translateY(-1px)}.question-card.level-border-1{border-top-color:var(--blue)}.question-card.level-border-2{border-top-color:var(--amber)}.question-card.level-border-3{border-top-color:var(--mint)}.card-meta{display:flex;align-items:center;gap:7px;padding-right:29px;color:var(--mint);font:10px ui-monospace,monospace}.level-dot{color:#8c9f9a}.level-dot.level-1{color:var(--blue)}.level-dot.level-2{color:var(--amber)}.level-dot.level-3{color:var(--mint)}.star{position:absolute;top:12px;right:12px;width:25px;height:25px;border:0;background:transparent;color:#a5b7b2;font-size:19px;line-height:1}.star:hover,.star.is-favorite{color:var(--amber)}.question-card h2{display:-webkit-box;overflow:hidden;margin:18px 23px 0 0;font-size:14px;line-height:1.55;-webkit-box-orient:vertical;-webkit-line-clamp:4}.card-foot{display:flex;align-items:center;justify-content:space-between;gap:6px;margin-top:auto;padding-top:12px;border-top:1px solid #edf3f1}.mastery-select{max-width:76px;padding:4px 3px;border:1px solid var(--line);border-radius:4px;background:#fff;color:#6a817b;font-size:10px;outline:0}.mastery-select.level-1{border-color:#b9cde6;color:var(--blue)}.mastery-select.level-2{border-color:#e5cda5;color:var(--amber)}.mastery-select.level-3{border-color:#a9dacc;color:var(--mint)}.open-answer{color:#6aada0;font-size:10px;white-space:nowrap}.empty{grid-column:1/-1;display:grid;place-items:center;padding:56px 18px;border:1px dashed #cadcd6;border-radius:7px;background:rgba(255,255,255,.55);text-align:center}.empty strong{color:#9fb4ae;font-size:24px}.empty h2{margin:10px 0 5px;font-size:16px}.empty p{margin:0;color:#839893;font-size:11px;line-height:1.7}
.answer-panel{position:sticky;top:82px;min-height:540px;padding:22px 24px;border:1px solid var(--line);border-radius:7px;background:#fff}.answer-head{display:flex;align-items:center;justify-content:space-between;color:var(--mint);font:10px ui-monospace,monospace}.answer-head>div{display:flex;align-items:center;gap:6px}.star.inline{position:static;width:25px}.answer-panel>h2{margin:16px 28px 6px 0;font-size:21px;line-height:1.45}.answer-tag{display:inline-flex;padding:4px 7px;border-radius:4px;background:#f0f6f4;color:#79918b;font-size:10px}.answer-content{max-height:590px;margin-top:16px;overflow:auto;padding:3px 5px 3px 2px;color:#506d66;font-size:12px;line-height:1.85}.answer-content p{margin:0 0 12px;padding-left:10px;border-left:3px solid #d6ebe4}.answer-content h4{margin:20px 0 8px;color:var(--ink);font-size:13px;text-decoration:underline;text-decoration-color:#8acbbd;text-decoration-thickness:2px;text-underline-offset:4px}.answer-content ul,.answer-content ol{margin:9px 0 15px;padding:0;list-style:none;counter-reset:answer-point}.answer-content li{position:relative;margin:9px 0;padding:10px 12px 10px 35px;border:1px solid #d9ebe5;border-left:4px solid var(--mint);border-radius:5px;background:#f5fbf8;font-weight:500}.answer-content ol li{counter-increment:answer-point}.answer-content ol li::before{content:counter(answer-point);position:absolute;left:10px;top:10px;color:var(--mint);font-weight:800}.answer-content ul li::before{content:'•';position:absolute;left:13px;top:8px;color:var(--mint);font-size:18px;font-weight:800}.answer-content strong{color:#0f7e6d;font-weight:800}.answer-content code{padding:2px 4px;border-radius:3px;background:#edf4f1;color:#b04d3c}.answer-content pre{overflow:auto;padding:12px;border-radius:5px;background:#162d2d;color:#dff1ea;font:11px/1.7 ui-monospace,monospace}.write-answer{margin-top:18px;width:100%;min-height:37px;border:1px solid #9bd2c5;border-radius:5px;background:var(--mint-soft);color:var(--mint);font-size:11px}.write-answer:hover{background:#d6f1e9}.note-editor{margin-top:18px}.editor-head{display:flex;justify-content:space-between;align-items:baseline;margin-bottom:9px}.editor-head strong{color:var(--ink);font-size:13px}.editor-head span{color:#9aaca7;font-size:10px}.note-editor textarea,.practice-editor textarea{width:100%;min-height:220px;padding:13px;resize:vertical;border:1px solid #a9d8cd;border-radius:6px;outline:0;color:var(--ink);background:#fbfefd;font-size:12px;line-height:1.8}.note-editor textarea:focus,.practice-editor textarea:focus{box-shadow:0 0 0 3px #edf9f5}.editor-actions,.practice-actions{display:flex;gap:9px;margin-top:12px}.secondary,.primary{min-height:35px;padding:0 13px;border-radius:5px;font-size:11px}.secondary{border:1px solid #b9ddd3;background:#fff;color:var(--mint)}.primary{border:0;background:var(--mint);color:#fff}.practice-card{max-width:900px;margin:28px auto 0;padding:34px 38px 25px;border:1px solid var(--line);border-radius:8px;background:#fff;box-shadow:var(--shadow)}.practice-meta{display:flex;align-items:center;justify-content:space-between;color:var(--mint);font:10px ui-monospace,monospace}.practice-card h2{margin:18px 0 23px;font-size:clamp(22px,3vw,31px);line-height:1.45}.practice-editor{display:grid;gap:10px}.practice-editor .primary{justify-self:start}.practice-reference{margin-top:18px;padding:16px 17px;border:1px solid #cfe9e0;border-radius:6px;background:#f3fbf8}.next-button{margin-left:auto}.mastery-summary{display:flex;flex-wrap:wrap;gap:7px;margin-bottom:16px}.review-filter{padding:8px 11px;border:1px solid var(--line);border-radius:5px;background:#fff;color:#6e8983;font-size:10px}.review-filter.is-active,.review-filter:hover{border-color:#95d1c3;background:var(--mint-soft);color:var(--mint)}.review-filter b{margin-left:5px}.progress-track{height:7px;overflow:hidden;border-radius:4px;background:#dcebe5}.toast{position:fixed;left:50%;bottom:25px;z-index:20;transform:translate(-50%,15px);padding:9px 13px;border-radius:5px;background:var(--deep);color:#fff;font-size:11px;opacity:0;pointer-events:none;transition:.2s}.toast.is-visible{transform:translate(-50%,0);opacity:1}.pagination{display:flex;justify-content:center;align-items:center;gap:5px;min-height:36px;margin-top:21px}.pagination button{min-width:32px;height:31px;padding:0 8px;border:1px solid #d6e4df;border-radius:5px;background:#fff;color:#6c8580;font-size:10px}.pagination button:hover:not(:disabled),.pagination button.is-active{border-color:#9bd2c5;background:var(--mint-soft);color:var(--mint)}.pagination button:disabled{opacity:.35;cursor:default}.pagination span{padding:0 3px;color:#a2b3ae}
@media(max-width:1100px){.view{padding:32px 28px 50px}.topbar{padding:0 28px}.question-list{grid-template-columns:repeat(2,minmax(0,1fr))}.browse-grid{grid-template-columns:minmax(0,1fr) 360px}}
@media(max-width:760px){.app-shell{display:block}.sidebar{position:fixed;inset:0 auto 0 0;z-index:10;width:246px;transform:translateX(-100%);transition:transform .2s;box-shadow:16px 0 35px rgba(15,39,37,.22)}.sidebar.is-open{transform:translateX(0)}.menu-toggle{display:grid}.topbar{gap:12px;padding:0 18px}.breadcrumb{margin-right:auto}.search-box{width:37px;border:0;background:transparent;padding:0}.search-box input,.search-box kbd{display:none}.view{padding:28px 18px 44px}.browse-grid{display:block}.answer-panel{position:static;min-height:0;margin-top:14px}.answer-content{max-height:none}.hero-row{align-items:flex-start}.practice-card{padding:27px 20px 20px}}
@media(max-width:500px){.question-list{grid-template-columns:1fr}.question-card{aspect-ratio:1/.76}.hero-row{display:block}.metric{display:inline-flex;align-items:baseline;gap:6px;margin-top:16px;padding:0;border:0}.metric strong{display:inline}.toolbar{align-items:flex-start;flex-direction:column;gap:10px}.toolbar-controls{width:100%;justify-content:space-between}.topic-scroller{flex-wrap:nowrap;overflow:auto;padding-bottom:3px}.practice-actions,.editor-actions{flex-wrap:wrap}.next-button{margin-left:0;width:100%}.secondary,.primary{flex:1}}

/* Keep answer hierarchy readable without turning every line into a banner. */
.answer-content p{padding-left:0;border-left:0;margin-bottom:13px}
.answer-content li{margin:6px 0;padding:5px 8px 5px 28px;border:0;border-left:2px solid #c8e4db;border-radius:0;background:transparent;font-weight:400}
.answer-content ol li::before{left:7px;top:5px;color:var(--mint)}
.answer-content ul li::before{left:9px;top:3px;color:var(--mint);font-size:15px}
.answer-content strong{color:#116f62;font-weight:800}
.answer-content em{color:#8a5d22;font-style:normal}
.answer-content u{text-decoration-color:#d1953f;text-decoration-thickness:2px;text-underline-offset:3px}
.answer-content mark{padding:1px 4px;border-radius:3px;background:#fff0bd;color:#795700}
.answer-content pre{background:#162d2d;color:#dff1ea}
.answer-content pre code{padding:0;background:transparent;color:inherit;border-radius:0}
.answer-panel{scroll-margin-top:82px}
.answer-close{display:none;border:0;background:transparent;color:#78908a;font-size:26px;line-height:1;width:30px;height:30px}
@media(max-width:760px){
  .answer-panel.is-open{position:fixed;inset:0;z-index:30;display:block;overflow:auto;margin:0;padding:22px 18px 34px;border:0;border-radius:0;min-height:100dvh;background:#fff;animation:answer-in .18s ease-out}
  .answer-panel.is-open .answer-close{display:grid;place-items:center}
  .answer-panel.is-open .answer-content{max-height:none}
  @keyframes answer-in{from{opacity:0;transform:translateY(14px)}to{opacity:1;transform:translateY(0)}}
}