/* 教学图片及数学排版；窄屏内部滚动，避免撑开整页。 */
.math-panel{background:#f7f9ff;border:1px solid #dbe3f3;border-radius:12px;padding:14px;margin:8px 0 18px;min-width:0}
.math-row{overflow-x:auto;overflow-y:hidden;padding:8px 2px;max-width:100%;font-size:1.06rem}
.math-row .katex-display{margin:.3em 0;text-align:left}
.math-row .katex-display>.katex{text-align:left}
.math-panel details{font-size:.85rem;color:#62718a;margin-top:12px}
.math-panel summary{cursor:pointer}
.formula-copy{white-space:pre-wrap;font-family:inherit;line-height:1.8}
.diagram-button{display:block;background:white;border:1px solid #dce4f0;padding:0;border-radius:12px;width:100%;overflow:hidden;cursor:zoom-in}
.diagram-button img{display:block;width:100%;height:auto}
.diagram-button:focus-visible{outline:3px solid #2563eb;outline-offset:3px}
.diagram-caption{font-size:.88rem;line-height:1.7;color:#52627a;margin:10px 0 4px}
#lesson-figure{margin:24px 0}
#lesson-figure small{color:#76849b}
.diagram-dialog{width:min(1120px,94vw);max-width:94vw;max-height:92vh;padding:20px;border:1px solid #dce4f0;border-radius:16px;overflow:auto}
.diagram-dialog::backdrop{background:rgb(15 23 42 / .65)}
.diagram-dialog img{display:block;width:100%;height:auto}
.diagram-dialog p{line-height:1.7;color:#52627a}
.diagram-close{display:block;margin-left:auto;position:sticky;top:0}
.study,.tools,.lesson-card,.tool-card{min-width:0}
@media(max-width:650px){.math-panel{padding:10px}.math-row{font-size:.94rem}.diagram-dialog{padding:10px}.diagram-caption{font-size:.82rem}}

.math-label{display:block;color:#62718a;font-size:.78rem;margin:6px 0 0}

/* 图在上、两栏独立滚动；滚动边界不传递到另一栏或整页。 */
body{height:100vh;height:100dvh;display:flex;flex-direction:column;overflow:hidden}
.topbar{flex:none;padding:12px 24px}
main#workspace{flex:1;min-height:0;width:100%;max-width:1720px;margin:12px auto;padding:0 18px 12px;display:grid;grid-template-columns:220px minmax(0,1fr);gap:16px;overflow:hidden;align-items:stretch}
.sidebar{position:static;grid-row:auto;min-height:0;max-height:none;overflow:auto;overscroll-behavior:contain}
.study{grid-column:2;min-height:0;height:100%}
.split-lesson{height:100%;min-height:0;padding:16px;margin:0;display:grid;grid-template-rows:auto auto minmax(0,1fr) auto;gap:10px;overflow:hidden}
.lesson-heading h2{font-size:21px;margin:3px 0}
.lesson-heading .goal{font-size:12px;margin:0;padding:0;border:0}
.split-lesson #lesson-figure{margin:0;min-width:0;display:grid;grid-template-columns:minmax(0,1fr) 220px;column-gap:14px;align-content:center;align-items:center}
.split-lesson #lesson-figure h3{display:none}
.split-lesson #lesson-figure .diagram-button{grid-row:1/3;grid-column:1}
.split-lesson .diagram-button img{width:100%;height:clamp(90px,19dvh,170px);object-fit:contain}
.split-lesson .diagram-caption{font-size:12px;margin:0;line-height:1.55}
.split-lesson #lesson-figure small{font-size:11px}
.split-columns{display:grid;grid-template-columns:minmax(0,1.1fr) minmax(0,1fr);gap:14px;min-height:0;overflow:hidden}
.study-pane{display:flex;flex-direction:column;min-width:0;min-height:0;overflow:hidden;border:1px solid #dce7eb;border-radius:12px}
.split-lesson section{margin-top:0}
.pane-toolbar{display:flex;flex:none;gap:6px;align-items:center;flex-wrap:wrap;padding:8px 10px;background:#f4f8f9;border-bottom:1px solid #dce7eb}
.pane-toolbar strong{font-size:13px;margin-right:auto}
.pane-toolbar button,.mobile-study-tabs button{padding:5px 12px;font-size:13px}
.pane-toolbar button[aria-pressed=true],.mobile-study-tabs button[aria-pressed=true]{background:#117a70;color:white;border-color:#117a70}
.pane-scroll{flex:1;min-height:0;overflow-y:auto;overflow-x:hidden;overscroll-behavior:contain;scrollbar-gutter:stable;padding:16px;overflow-wrap:anywhere}
#explanation-scroll>section{margin:0 0 24px}
#explanation-scroll h3{font-size:17px}
#practice-scroll .tool-card{padding:0;border:0;margin:0;border-radius:0}
#quiz h2{font-size:18px;margin:0 0 10px}
.quiz-number{display:grid;grid-template-columns:max-content minmax(60px,1fr) max-content;max-width:100%;gap:8px}
.quiz-number span{white-space:nowrap}
.split-lesson .lesson-pager{margin:0;align-items:center}
.lesson-pager button{padding:6px 12px}
.lesson-pager small{font-size:11px;color:#71858e}
.mobile-study-tabs,#course-toggle{display:none}
@media(max-width:1000px){main#workspace{grid-template-columns:180px minmax(0,1fr);padding:0 10px 10px;gap:10px}.split-lesson{padding:12px}.split-columns{gap:10px}.pane-scroll{padding:12px}.split-lesson #lesson-figure{grid-template-columns:minmax(0,1fr) 150px}.sidebar-head{padding:14px}}
@media(max-width:760px){
.topbar{padding:8px 12px;align-items:center;gap:10px}.topbar .brand small,.topbar nav>a:first-of-type{display:none}.topbar nav{flex-direction:row;align-items:center;gap:10px}.brand strong{font-size:16px}.mark{width:34px;height:34px}.brand{gap:7px}
#course-toggle{display:block;padding:5px 8px;font-size:12px}
main#workspace{display:block;position:relative;margin:8px auto 0;padding:0 8px 8px}
.sidebar{display:none;position:absolute;z-index:5;inset:0 8px 8px;width:auto;max-height:none;box-shadow:0 6px 22px #20334833}
.sidebar.is-open{display:block}
.study{width:100%;height:100%}
.split-lesson{grid-template-rows:auto auto auto minmax(0,1fr) auto;gap:7px;padding:10px}
.lesson-heading h2{font-size:18px}.lesson-heading .goal{display:none}
.split-lesson #lesson-figure{display:block}.split-lesson .diagram-button img{height:clamp(75px,16dvh,125px)}
.split-lesson .diagram-caption,.split-lesson #lesson-figure small{display:none}
.mobile-study-tabs{display:flex;gap:8px}.mobile-study-tabs button{flex:1}
.split-columns{display:block;height:100%}.study-pane{height:100%}
.split-columns[data-mobile-pane=explanation] #practice-pane,.split-columns[data-mobile-pane=practice] #explanation-pane{display:none}
.lesson-pager small{display:none}.pane-scroll{padding:12px}
}