/* Figma V3: shared website tokens, responsive content, and one-shot hint motion. */
:root{--bx-bg:#f5f6f8;--bx-paper:#fff;--bx-ink:#20242c;--bx-muted:#687180;--bx-line:#e5e8ee;--bx-orange:#2563eb;--bx-orange-dark:#1d4ed8;--bx-blue:#2563eb;--bx-mint:#227d5a;--bx-soft-orange:#f0f5ff;--bx-soft-blue:#f0f5ff;--bx-soft-mint:#f6f8fa;--bx-soft-coral:#f7f9fc;--bx-soft-violet:#f7f9fc;--bx-radius:12px;--bx-shadow:none;--bx-font:"Noto Sans SC","PingFang SC","Microsoft YaHei",system-ui,sans-serif}
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.study-title h1{font-size:22px}.study-title button{min-height:44px}.study-context-bar,.study-retention,.study-save-note{color:var(--bx-muted)}.study-chat-surface{border:1px solid var(--bx-line);border-radius:12px}.study-message>.chat-rich,.study-message.user>.chat-rich{background:#fff;border:0;border-radius:12px;color:var(--bx-ink);font-size:15px;line-height:1.8}.study-message.user>.chat-rich{background:#f1f4f8}.study-message>small{color:var(--bx-muted)}.study-attachment{background:#fff;border-color:var(--bx-line)}.study-attachment span small{color:var(--bx-muted)}.study-question-card{background:#fff;border:1px solid var(--bx-line);border-radius:12px;min-width:0}.study-question-stem{font-size:16px}.study-source-options>div,.study-own-work{background:#f7f9fc;border-color:var(--bx-line);border-radius:10px}.study-verdict{border-radius:6px}.study-composer{background:#fff;border-top:1px solid var(--bx-line);align-items:flex-end}.study-composer textarea{background:#f7f9fc;border:1px solid var(--bx-line);border-radius:10px;min-height:44px;font-size:16px;max-height:120px}.study-composer .primary{min-width:64px}.study-history-tabs button{min-height:44px;border-radius:10px}.study-history-tabs button.active{background:#f0f5ff;color:#2563eb}.study-history-item{background:#fff;border-color:var(--bx-line);border-radius:12px}.study-history-icon{background:#f0f5ff;color:#2563eb}.study-upload{border-color:var(--bx-line);background:#fff;border-radius:12px;box-shadow:none}.study-upload-illustration{background:#f0f5ff;color:#2563eb}.study-upload h2{font-size:20px}.study-working{color:var(--bx-muted)}.study-image-viewer{max-width:100%;overflow:auto;max-height:72dvh;touch-action:pan-x pan-y pinch-zoom}.study-image-viewer img{width:auto;max-width:100%;height:auto;max-height:none;margin:auto}.study-image-viewer.zoomed img{max-width:none;width:auto;min-width:140%;height:auto}.chat-rich{overflow-wrap:anywhere;min-width:0;line-height:1.8}.chat-rich img{max-width:100%;height:auto}.chat-rich pre,.chat-rich .katex-display{overflow-x:auto;max-width:100%}.chat-rich table{display:block;overflow:auto;max-width:100%}.chat-rich code{white-space:pre-wrap}
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.lesson-coach{background:#fff;border-color:var(--bx-line);border-radius:12px}.lesson-coach header{color:var(--bx-ink)}.lesson-coach-step{background:#f0f5ff;color:var(--bx-ink);border-radius:10px;animation:kf_52_2934_opacity_0 2s linear 1 both,kf_52_2934_y_0 2s linear 1 both}.lesson-coach-step small{display:none}.bx-hint-bubble{background:#f0f5ff;color:var(--bx-ink);border:1px solid #bbcff9;border-radius:12px;box-shadow:0 4px 18px #1e345216;transform-origin:0 0;animation:kf_52_2913_opacity_0 2s linear 1 both,kf_52_2913_y_0 2s linear 1 both}.bx-hint-bubble:before{background:#f0f5ff;border-color:#bbcff9}.bx-hint-bubble>small{color:#2563eb}.bx-hint-close{color:var(--bx-muted);width:36px;height:36px;display:grid;place-items:center}.bx-hint-actions button{min-height:44px;border-radius:10px}.hint-target-active{outline:2px solid #2563eb!important;animation:none}.bx-hint-keyword{background:#dbe8ff}.bx-hint-pin{border-color:#2563eb;background:#2563eb22;animation:none}
@keyframes kf_52_2913_opacity_0{0%,8%{opacity:0;animation-timing-function:ease-out}19%,100%{opacity:1}}@keyframes kf_52_2913_y_0{0%,8%{transform:translateY(8px);animation-timing-function:ease-out}19%,100%{transform:translateY(0)}}@keyframes kf_52_2934_opacity_0{0%,21%{opacity:0;animation-timing-function:ease-out}32%,100%{opacity:1}}@keyframes kf_52_2934_y_0{0%,21%{transform:translateY(8px);animation-timing-function:ease-out}32%,100%{transform:translateY(0)}}
.ebook-toolbar{background:#fff;border-color:var(--bx-line);border-radius:12px;gap:6px;flex-wrap:nowrap;overflow-x:auto;scrollbar-width:thin}.ebook-toolbar button{flex-shrink:0;min-height:44px;border-radius:10px}.ebook-page{background:#fff;border-color:var(--bx-line)}.speaker-large{background:#f0f5ff;color:#2563eb;border-color:#bbcff9}.dictation-source,.dictation-card{background:#fff;border-color:var(--bx-line);border-radius:12px}.listen-choice,.listen-controls button{border-radius:12px;min-height:46px}.admin-stat,.analytics-panel,.analytics-card{background:#fff;border-radius:12px;border-color:var(--bx-line)}.analytics-bar i{background:#2563eb}
@media(max-width:1023px){.desktop-sidebar,.topbar{display:none!important}.app-main{margin-left:0}.web-header{height:60px;display:flex;align-items:center;justify-content:space-between;padding:8px 16px;background:#fff;border-bottom:1px solid #f2f4f7}.web-brand{display:flex;gap:8px;align-items:center;font-size:18px;font-weight:700;padding:0;min-height:44px}.web-brand img{width:28px;height:28px;object-fit:contain}.web-header nav{display:flex;gap:8px}.web-header nav button{min-width:52px;min-height:44px;font-size:13px;padding:8px}.page{padding:20px 16px 24px;max-width:800px;margin:auto}.web-home{max-width:640px}.study-messages{max-height:calc(var(--learning-vh,100dvh) - 326px);min-height:160px}.study-title h1{font-size:20px}.study-title button{font-size:12px;padding:7px 9px}.study-title>div{gap:4px}.study-context-bar{font-size:12px}.study-context-bar button{min-height:44px}.study-message>.chat-rich{font-size:15px}.study-title{gap:8px}.study-upload{margin:10px 0}.study-upload p{font-size:14px}.study-composer{padding:10px}.lesson-toolbar{top:0}.lesson-question-list strong{font-size:14px}.lesson-question-list>button{gap:8px}.lesson-question-list small{font-size:11px}.lesson-step-nav{gap:6px}.lesson-step-nav>span{font-size:11px}.lesson-chapter-list>button{padding:12px}.auth-page{padding:20px 16px;min-height:100dvh}.auth-card{padding:22px 20px}.auth-welcome{display:none}body[data-view=arena] .page{padding:12px 16px 24px}.lesson-fixed-actions{padding:12px 0 max(12px,env(safe-area-inset-bottom));margin-left:0;margin-right:0;bottom:0}.dictation-stage{padding-bottom:0}.ebook-toolbar{position:sticky;top:0}.reader-layout{min-width:0}}
@media(min-width:651px) and (max-width:1023px){.web-home{max-width:640px}.web-tool.major{min-height:112px}.web-mybooks{grid-template-columns:1fr 1fr}.web-mybooks>.between,.web-reading-resume{grid-column:1/-1}.page{padding-top:24px}}
@media(max-width:360px){.web-greeting h1{font-size:16px}.web-tool.major strong{font-size:15px}.web-tools{gap:10px}.web-tool{padding:10px}.web-tool strong{font-size:13px}.web-tool.major{padding:12px}.web-tool small{font-size:11px}.lesson-secondary-actions button{font-size:12px}.study-title h1{font-size:18px}.study-title{align-items:flex-start}.study-title>div{justify-content:flex-end}.lesson-primary-actions{gap:8px}.lesson-primary-actions>button{padding:10px 8px}.lesson-question-list>button{flex-wrap:wrap}.web-menu{grid-template-columns:1fr}}
@media(max-width:650px){.web-mybooks{grid-template-columns:repeat(3,minmax(0,1fr));gap:8px}.web-mybooks>.between,.web-reading-resume{grid-column:1/-1}.web-book-row{padding:10px;align-items:flex-start}.web-book-row>span{width:100%}.web-book-row>svg{display:none}.web-book-row strong{font-size:13px;line-height:1.6}.web-book-row small{font-size:11px;line-height:1.6}.web-reading-resume{font-size:12px}}
@media(max-height:650px) and (max-width:650px){.page{padding-top:12px}.web-home{gap:10px}.web-greeting h1{font-size:16px}.web-tool.major{min-height:96px}.web-stats strong{font-size:20px}.study-messages{min-height:100px;max-height:calc(var(--learning-vh,100dvh) - 280px)}}
@media(prefers-reduced-motion:reduce){.bx-hint-bubble,.lesson-coach-step,.hint-target-active,.bx-hint-pin,.page{animation:none!important;transform:none}.primary,.secondary{transition:none}}
body:has([data-lesson-question]) .page{padding-bottom:160px}.lesson-fixed-actions{position:fixed;left:224px;right:0;bottom:0;max-width:1184px;margin:0 auto;padding:12px 24px max(12px,env(safe-area-inset-bottom));box-shadow:0 -3px 12px #24364b06}.lesson-ficon{filter:grayscale(1)}
@media(max-width:1023px){.web-header{position:sticky;top:0;z-index:40}.lesson-toolbar{top:60px}.lesson-fixed-actions{left:0;right:0;max-width:800px;padding:12px 16px max(12px,env(safe-area-inset-bottom));margin:0 auto}.ebook-toolbar{top:60px}body:has([data-lesson-question]) .page{padding-bottom:160px}}
.lesson-fixed-actions{bottom:var(--learning-bottom,0px)}html{scroll-padding-top:112px;scroll-padding-bottom:160px}#lesson-answer{scroll-margin-top:112px;scroll-margin-bottom:160px}
.lesson-image-button img{width:100%;max-width:100%;height:auto;max-height:none}.bx-hint-bubble{overflow:auto;overscroll-behavior:contain}
.parent-quote{background:#fff;border:1px solid var(--bx-line);border-radius:12px;padding:12px 16px}.parent-quote summary{min-height:44px;display:flex;align-items:center;font-size:15px;font-weight:600;cursor:pointer}.parent-quote summary:after{content:'＋';margin-left:auto;color:#687180}.parent-quote[open] summary:after{content:'－'}.parent-encouragement-body textarea{height:76px;min-height:76px;margin:8px 0;font-size:16px}.parent-chart{border-color:var(--bx-line);border-radius:12px;background:#fff}
@media(max-width:1023px){.report-headline{font-size:18px;margin:14px 0}.report-headline em{font-size:24px}.parent-summary{gap:10px;margin:12px 0}.parent-summary .metric-tile{padding:12px;min-height:88px;border-radius:12px}.parent-summary .metric-tile strong{font-size:24px;line-height:1.5}.parent-summary .metric-tile strong small{font-size:11px;display:inline;margin-left:4px}.parent-summary .metric-tile span{font-size:12px}.parent-report-layout{gap:12px}.parent-chart{padding:14px}.parent-chart .bar-chart{height:120px}.parent-chart p{font-size:12px;color:var(--bx-muted)}.parent-export{display:inline-flex;width:calc(50% - 6px)!important;min-height:44px;font-size:12px;margin:12px 4px 0 0;padding:8px;border:1px solid var(--bx-line);border-radius:10px;color:var(--bx-muted);justify-content:center}.parent-report-layout .section-title{margin:12px 0 8px}}
@media(min-width:700px) and (max-width:1023px){.parent-report-layout{grid-template-columns:minmax(0,1.1fr) minmax(0,1fr);align-items:start}}

/* Complete question image controls and a compact source review workbench. */
.bx-image-tools{display:flex;align-items:center;gap:6px;flex-wrap:wrap;margin:10px 0}.bx-image-tools button{min-height:44px;padding:8px 12px}.bx-image-tools output{min-width:44px;text-align:center;font-size:13px;font-variant-numeric:tabular-nums}.bx-image-status{font-size:12px;color:var(--bx-muted);margin:6px 0}.bx-image-stage{width:100%;max-height:62dvh;overflow:auto;overscroll-behavior:contain;touch-action:pan-x pan-y pinch-zoom;background:#f4f6f8;border:1px solid var(--bx-line);border-radius:10px}.bx-image-stage img{display:block;max-width:none;max-height:none;height:auto;margin:0}.bx-image-stage img[hidden]{display:none}.review-filters{display:grid;grid-template-columns:2fr 1fr 1fr 1fr auto;align-items:end;gap:10px;margin:14px 0}.review-filters label{display:grid;gap:5px;font-size:12px;min-width:0}.review-filters select,.review-filters input{width:100%;min-width:0;max-width:100%;min-height:44px;border:1px solid var(--bx-line);border-radius:8px;padding:8px;font:inherit;font-size:13px;background:#fff}.review-counts{font-size:13px;color:var(--bx-muted);padding:10px 0}.review-question-list{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));align-items:start;gap:12px}.review-question-card{min-width:0;border:1px solid var(--bx-line);border-radius:12px;padding:14px;background:#fff;overflow-wrap:anywhere}.review-question-card h2{font-size:15px;line-height:1.6;margin:0}.review-question-card p{font-size:12px;color:var(--bx-muted)}.review-question-card .between{flex-wrap:wrap;gap:8px}.review-question-card .lesson-image-button img{max-width:100%;width:100%;height:auto;max-height:280px;object-fit:contain;object-position:top}.review-question-card details{font-size:13px;margin:10px 0}.review-actions{display:flex;gap:7px;flex-wrap:wrap}.review-actions button{min-height:44px;font-size:13px}.lesson-answer-heading{flex-wrap:wrap;gap:6px}.lesson-answer-heading [hidden]{display:none}
@media(max-width:760px){.review-filters{grid-template-columns:1fr 1fr}.review-filters label:first-child{grid-column:1/-1}.review-question-list{grid-template-columns:1fr}.bx-image-stage{max-height:58dvh}}
.lesson-source-figure,.lesson-continuation,.lesson-reading>.lesson-image-button{max-height:clamp(180px,46dvh,430px);overflow:auto;overscroll-behavior:contain;scrollbar-gutter:stable;touch-action:pan-x pan-y pinch-zoom}.lesson-source-figure>.lesson-image-button{display:block;width:100%;padding:0;border:0;min-height:0}.lesson-source-figure img,.lesson-continuation img,.lesson-reading img{display:block;width:100%;max-width:100%;height:auto;max-height:none;object-fit:contain;object-position:top}.lesson-source-figure::after{content:'图示可上下滑动 · 点按可放大';display:block;position:sticky;bottom:0;padding:4px 8px;font-size:11px;text-align:center;background:rgba(255,255,255,.94);color:var(--bx-muted);pointer-events:none}

.lesson-source-figure{--figure-height:clamp(200px,40dvh,430px);max-height:calc(var(--figure-height) + 28px)}.lesson-source-figure>.lesson-image-button{display:flex;justify-content:center;align-items:flex-start}.lesson-source-figure img{width:auto;max-width:100%;max-height:var(--figure-height);height:auto;margin:0 auto}.lesson-source-figure.is-tall{max-height:var(--figure-height)}.lesson-source-figure.is-tall img{width:100%;max-height:none}.lesson-source-figure::after{content:'点按查看完整大图 · 支持缩放和滑动'}.lesson-options:has(button span:first-of-type){min-width:0}@media(max-width:760px){.lesson-options{gap:8px}.lesson-options>button{font-size:14px;padding:9px 10px;min-height:44px}}

.lesson-generated-stem{font-size:17px;line-height:1.9;padding:12px 0;color:var(--bx-ink)}.lesson-generation{border:1px solid var(--bx-line);border-radius:12px;padding:14px;margin:14px 0;background:#fff}.lesson-generation .between{gap:10px;flex-wrap:wrap}.lesson-generation h2{font-size:16px;margin:0}.lesson-generation p{font-size:12px;color:var(--bx-muted);line-height:1.8;margin:7px 0}.lesson-generation button{min-height:44px}.lesson-generation [role=status]{font-size:13px;color:var(--bx-ink)}
.lesson-question-tags{display:flex;flex-wrap:wrap;gap:6px;margin:4px 0 10px;min-width:0}.lesson-question-tags>span{max-width:100%;overflow-wrap:anywhere;font-size:11px;line-height:1.6;color:var(--bx-muted);border:1px solid var(--bx-line);border-radius:6px;padding:3px 7px;background:#fff}.lesson-generated-figure img{max-height:clamp(180px,35dvh,360px);width:auto}.lesson-generation-roles summary{font-size:12px;min-height:44px;display:flex;align-items:center;cursor:pointer;color:var(--bx-muted)}.lesson-generation [role=status]{overflow-wrap:anywhere;margin-top:8px;line-height:1.7}.lesson-generation .text-action{margin-top:6px}.lesson-parent-reference{min-width:0;overflow-wrap:anywhere;font-size:14px;line-height:1.8}.lesson-parent-reference h4{font-size:14px;margin:16px 0 7px}.lesson-parent-reference h3{font-size:16px;line-height:1.7}.lesson-solution-steps{padding-left:22px}.lesson-solution-steps li{padding-left:4px;margin:8px 0}.lesson-quality-records{margin-top:16px}.lesson-quality-records summary{min-height:44px;font-size:13px;cursor:pointer}.lesson-quality-records>p{font-size:12px;color:var(--bx-muted)}.lesson-quality-records section{border-top:1px solid var(--bx-line);padding:10px 0}.lesson-quality-records strong,.lesson-quality-records small{display:block}.lesson-quality-records small{font-size:11px;color:var(--bx-muted);overflow-wrap:anywhere}.lesson-quality-records section p{font-size:12px;margin:6px 0}.lesson-progress-segments{max-width:100%;overflow:hidden}.lesson-progress-segments>i{min-width:0;flex:1}.lesson-source-figure,.lesson-generated-stem,.lesson-continuation{scroll-margin-top:112px;scroll-margin-bottom:170px}.lesson-fixed-actions{box-sizing:border-box}#lesson-answer{scroll-margin-bottom:200px}
@media(max-width:480px){.lesson-question{padding:12px}.lesson-toolbar{gap:4px}.lesson-toolbar button{padding:6px 7px}.lesson-toolbar>strong{font-size:14px}.lesson-secondary-actions{gap:5px}.lesson-secondary-actions button{font-size:12px;min-width:0;padding:8px 5px}.lesson-generated-stem{font-size:16px}.lesson-generation{padding:12px}.lesson-generation .between>.primary{width:100%}.lesson-question-tags>span{font-size:10px}}
.lesson-layer-filters{border:1px solid var(--bx-line);border-radius:10px;padding:10px 12px;margin:10px 0;background:#fff;min-width:0}.lesson-layer-filters .study-history-tabs{margin:0 0 8px;flex-wrap:wrap}.lesson-layer-filters .study-history-tabs button{flex:1;min-width:60px;font-size:12px;padding:7px}.lesson-layer-filters label{font-size:12px;display:flex;align-items:center;gap:8px;min-width:0}.lesson-layer-filters select{flex:1;min-width:0;max-width:100%;min-height:44px;border:1px solid var(--bx-line);border-radius:8px;padding:8px;font:inherit;background:#fff}.lesson-layer-filters>small{display:block;font-size:11px;color:var(--bx-muted);margin-top:7px}
@media(max-width:760px){body:has(#lesson-answer:focus) .lesson-fixed-actions .lesson-secondary-actions{display:none}body:has(#lesson-answer:focus) #lesson-answer{scroll-margin-bottom:100px}}
.bx-hint-bubble.bx-hint-inline{position:relative;inset:auto;z-index:auto;width:100%;max-width:100%;max-height:none;margin:12px 0;box-shadow:none;transform:none;overflow:visible}.bx-hint-bubble.bx-hint-inline:before{display:none}.bx-hint-inline>small{display:block;padding-right:30px}.lesson-coach,.bx-hint-inline{scroll-margin-top:120px;scroll-margin-bottom:180px}.lesson-diagram-caption{font-size:13px;line-height:1.8;color:var(--bx-muted);white-space:pre-wrap;overflow-wrap:anywhere;margin:8px 0 12px}.lesson-coach footer{flex-wrap:wrap}.lesson-coach footer button{min-height:44px}.bx-hint-pin{pointer-events:none}
/* The mobile website uses its top header; no space is reserved for the old app tab bar. */
@media(max-width:650px){body[data-view=home] .page{padding-bottom:max(16px,env(safe-area-inset-bottom))}}
/* V4: one quiet location bar, one directory sheet, and two answer actions. */
.lesson-screen{min-width:0}.lesson-location{position:sticky;top:var(--arena-header-height,0px);z-index:35;display:flex;align-items:center;gap:8px;min-width:0;min-height:56px;padding:5px 0;background:#fff;border-bottom:1px solid var(--bx-line);margin-bottom:12px}.lesson-location button{flex-shrink:0;min-width:44px;min-height:44px;border:0;border-radius:8px;background:transparent;color:var(--bx-ink);padding:7px 8px;font-size:13px;display:inline-flex;align-items:center;justify-content:center;gap:5px}.lesson-location button:hover{background:#f4f6f9}.lesson-location-directory .icon,.lesson-location-directory svg{width:17px;height:17px}.lesson-location-current{min-width:0;flex:1}.lesson-location-current small{display:block;font-size:11px;line-height:1.5;color:var(--bx-muted);white-space:nowrap;overflow:hidden;text-overflow:ellipsis;font-weight:400}.lesson-location-current strong{display:block;overflow:hidden;white-space:nowrap;text-overflow:ellipsis;line-height:1.65;font-size:15px;font-weight:600;color:var(--bx-ink)}.lesson-location-current strong>span{font-size:11px;font-weight:400;color:var(--bx-muted);margin-left:8px}.lesson-location .lesson-location-more{font-size:16px;letter-spacing:1px}.lesson-location .lesson-location-return{font-size:12px;color:#2563eb}.lesson-question-summary{display:flex;align-items:center;justify-content:space-between;gap:8px;min-width:0;color:var(--bx-muted);font-size:12px;line-height:1.6;margin-bottom:8px}.lesson-question-summary>span{min-width:0;overflow-wrap:anywhere}.lesson-question-summary .text-action{min-width:36px;min-height:36px;padding:6px}.lesson-question{padding:0!important;margin-top:0}.lesson-question>.lesson-source-card{border:0;border-radius:0;padding:0;background:transparent}.lesson-question .lesson-generated-stem{font-size:16px;line-height:1.75;margin:4px 0 12px}.lesson-question .lesson-answer-heading{margin-top:18px}.lesson-question .lesson-options>button{min-height:48px;font-size:15px;border-radius:10px;padding:10px 12px}.lesson-question textarea#lesson-answer{min-height:82px}.lesson-fixed-actions{max-width:820px}.lesson-primary-actions{gap:10px}.lesson-step-nav{margin:12px 0;font-size:12px}.lesson-step-nav>span{color:var(--bx-muted)}.lesson-chapter-overview{border:0;border-radius:0;padding:8px 0 14px;margin:0}.lesson-chapter-overview h1{font-size:18px;line-height:1.6;margin:0 0 4px}.lesson-chapter-overview p{font-size:12px;line-height:1.6;overflow-wrap:anywhere;color:var(--bx-muted)}.lesson-chapter-continue{padding:10px 0 max(10px,env(safe-area-inset-bottom));background:#fff}.lesson-book-heading{padding:8px 0 14px;border:0;border-radius:0}.lesson-book-heading h2{font-size:17px;line-height:1.7;overflow-wrap:anywhere}.lesson-book-heading p{font-size:12px;line-height:1.6}.lesson-directory-sheet{min-width:0;overflow:auto;overscroll-behavior:contain}.lesson-directory-sheet header small,.lesson-menu-identity{font-size:12px;line-height:1.6;color:var(--bx-muted)}.lesson-directory-sheet header h3,.lesson-more-menu h3{font-size:16px;line-height:1.65;overflow-wrap:anywhere;margin:4px 0}.lesson-directory-sheet header p{font-size:12px;color:var(--bx-muted);margin:4px 0 10px}.lesson-directory-shortcuts{display:flex;align-items:center;flex-wrap:wrap;gap:4px;padding:2px 0 10px;border-bottom:1px solid var(--bx-line)}.lesson-directory-shortcuts .text-action{font-size:12px;min-height:40px;padding:6px 9px}.lesson-directory-sheet .lesson-chapter-drawer{display:grid;gap:0;max-height:none;overflow:visible}.lesson-directory-sheet .lesson-chapter-drawer>button{display:flex;align-items:center;gap:10px;width:100%;min-height:60px;text-align:left;border:0;border-bottom:1px solid #f1f3f6;border-radius:0;background:#fff;padding:10px 8px;color:var(--bx-ink)}.lesson-directory-sheet .lesson-chapter-drawer>button>b{font-size:12px;font-weight:400;color:var(--bx-muted);width:22px;flex-shrink:0}.lesson-directory-sheet .lesson-chapter-drawer>button>span{min-width:0;flex:1}.lesson-directory-sheet .lesson-chapter-drawer strong{display:block;font-size:14px;font-weight:500;line-height:1.6;overflow-wrap:anywhere}.lesson-directory-sheet .lesson-chapter-drawer small{display:block;font-size:11px;color:var(--bx-muted);line-height:1.6;margin-top:3px}.lesson-directory-sheet .lesson-chapter-drawer .active{background:#f4f7fc;border-left:2px solid #2563eb}.lesson-directory-sheet footer{border-top:1px solid var(--bx-line);padding-top:10px;display:flex;flex-direction:column;gap:4px}.lesson-directory-sheet footer .text-action{justify-content:flex-start;text-align:left;min-height:40px;font-size:13px;padding:6px 0}.lesson-directory-sheet footer small{font-size:11px;color:var(--bx-muted);line-height:1.6}.modal-backdrop:has(.lesson-directory-sheet){padding:0;align-items:stretch;justify-content:flex-end}.modal:has(.lesson-directory-sheet){width:min(400px,90vw);max-width:400px;max-height:100dvh;margin:0;border-radius:14px 0 0 14px;padding:16px;display:flex;flex-direction:column;overflow:hidden;animation:lessonDirectoryEnter .18s ease-out}.modal:has(.lesson-directory-sheet) .modal-head{flex-shrink:0;margin-bottom:8px}.modal:has(.lesson-directory-sheet) .modal-head h2{font-size:18px}.lesson-more-menu{display:grid;gap:0;min-width:0}.lesson-more-menu>button{display:flex;width:100%;justify-content:flex-start;min-height:44px;padding:10px 0;border:0;border-bottom:1px solid #f1f3f6;border-radius:0;background:transparent;font-size:14px;line-height:1.6;text-align:left;color:var(--bx-ink)}.lesson-menu-source{font-size:12px;line-height:1.8;color:var(--bx-muted);margin-top:8px;overflow-wrap:anywhere}.lesson-menu-source summary{min-height:44px;display:flex;align-items:center;cursor:pointer}.lesson-menu-source button{min-height:44px;font-size:12px}.lesson-menu-identity{margin:0}.arena-study-path{display:none}body:has([data-lesson-question]) .page{max-width:820px;padding-bottom:100px}body:has([data-lesson-question]) #lesson-answer{scroll-margin-top:90px;scroll-margin-bottom:110px}.arena-problem,.arena-work{border-radius:10px}.arena-unit-heading{font-size:12px}.arena-step-nav small{font-size:11px}
@keyframes lessonDirectoryEnter{from{transform:translateX(12px);opacity:.4}to{transform:translateX(0);opacity:1}}
@media(max-width:767px){.lesson-location{gap:5px;min-height:54px;margin-bottom:10px}.lesson-location-current strong{font-size:14px}.lesson-location-current small{font-size:11px}.lesson-location button{padding:7px 6px}.lesson-fixed-actions{padding:10px 16px max(10px,env(safe-area-inset-bottom))}.modal-backdrop:has(.lesson-directory-sheet){align-items:flex-end;justify-content:center}.modal:has(.lesson-directory-sheet){width:100%;max-width:none;max-height:88dvh;border-radius:16px 16px 0 0;padding:16px 16px max(16px,env(safe-area-inset-bottom))}.lesson-directory-sheet .lesson-chapter-drawer{max-height:none;overflow:visible}.lesson-location-directory .icon,.lesson-location-directory svg{display:none}.lesson-chapter-overview h1{font-size:17px}}
@media(prefers-reduced-motion:reduce){.modal:has(.lesson-directory-sheet){animation:none}}

.lesson-legacy-practice{padding:12px 0;border-top:1px solid var(--bx-line)}.lesson-legacy-practice h2{font-size:15px;font-weight:600;margin:0 0 5px}.lesson-legacy-practice>p{font-size:12px;line-height:1.7;color:var(--bx-muted);margin:0 0 8px}