:root{--font-text:"Microsoft YaHei UI","Microsoft YaHei","PingFang SC","Noto Sans CJK SC",sans-serif;--ink:#243c54;--muted:#6d7e8f;--line:#e3eaf0;--shell-width:224px}body{font-family:var(--font-text);background:#f4f7fa;color:var(--ink)}
.sidebar{width:var(--shell-width);padding:26px 18px 18px;background:#fcfdff;border-right:1px solid #e1e8f0;gap:0}.brand img{width:166px;height:54px;margin-left:7px}.sidebar .product-name{font-size:14px;font-weight:600;letter-spacing:.04em;color:#526a83;margin:15px 8px 28px}.sidebar .nav-caption{font-size:12px;font-weight:600;letter-spacing:.08em;color:#8c9bab;margin:0 12px 10px}.sidebar nav{gap:5px}.sidebar nav>a{padding:11px 12px;font-size:15px;min-height:46px;gap:12px;color:#587087;border-radius:11px}.sidebar nav>a>span{display:flex;align-items:center;justify-content:center;width:22px;font-size:15px;flex-shrink:0}.sidebar nav svg{width:20px;height:20px;display:block}.sidebar nav .course-nav{padding:13px 12px;align-items:center;gap:12px;border:1px solid transparent;position:relative}.sidebar nav .course-nav>span{width:28px;height:28px;background:transparent;font:600 14px/1 var(--font-text);color:#97a7b8;border:1px solid #dce5ef;border-radius:9px}.sidebar .course-nav b{font-size:15px;line-height:1.5;font-weight:600}.sidebar .course-nav small{font-size:13px;line-height:1.6;margin-top:3px;color:#7a8c9f}.sidebar nav a.active{background:#edf4ff;color:#2465b1;border-color:#dbe8fb}.sidebar nav .course-nav.active:before{content:"";position:absolute;left:-1px;width:3px;height:28px;border-radius:3px;background:#377cd0}.sidebar nav .course-nav.active>span{background:#fff;border-color:#c4d9f5;color:#2b70c5}.sidebar nav .course-nav.active small{color:#4c77a6}.sidebar nav .nav-tools-label{border-top:1px solid #e5ebf2;padding-top:20px;margin:17px 12px 6px}.sidebar-bottom{margin-top:auto;padding-top:25px;font-size:11px;text-align:left;display:flex;align-items:center;gap:7px;color:#91a0b0}.brand-dot{width:7px;height:7px;border-radius:50%;background:#f3c85f}.workspace{margin-left:var(--shell-width)}
.topbar{height:72px;padding:0 30px;background:rgba(255,255,255,.95);border-bottom:1px solid #e2e9f1;gap:16px}.crumb{display:flex;align-items:center;gap:13px;font-size:14px;min-width:0}.crumb-root{color:#8192a3;white-space:nowrap}.crumb-divider{color:#bac6d1}.crumb b{font-weight:500;color:#405d7b;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}.search-shortcut{margin-left:auto;border:1px solid #e4ebf3;background:#f7f9fc;border-radius:10px;min-width:190px;padding:8px 12px;gap:9px;font-size:13px}.search-shortcut svg{width:17px;height:17px}.search-shortcut kbd{margin-left:auto;color:#96a5b5}
main{max-width:1540px;margin:auto;padding:30px}.first-course-main{max-width:1600px!important;padding:28px!important}.l1-shell{grid-template-columns:192px minmax(0,1fr);gap:24px}.l1-menu{background:transparent;border:0;border-radius:0;padding:0 6px 0 0;top:20px;font-size:14px;scrollbar-width:thin;scrollbar-color:#d9e2ec transparent}.l1-menu>summary{font-size:16px;padding:8px 10px 15px;color:#344f6a}.l1-menu>summary>span{font-size:12px;line-height:1.8;color:#8394a5;margin-top:6px;font-weight:400}.l1-menu>details{border-top:0;margin-top:9px}.l1-menu>details>summary{padding:8px 10px;font-size:14px}.l1-menu>details>a{border-left:1px solid #dce5ef;border-radius:0;margin-left:14px;font-size:14px;padding:9px 12px;color:#708498}.l1-menu>details>a.current{background:#e8f1fc;color:#2168b4;border-left:2px solid #3c7fcb;border-radius:0 8px 8px 0}.l1-menu>a{font-size:14px;margin:5px 0}.l1-reading{background:#fff;border:1px solid #e1e8ef;border-radius:22px;padding:28px;box-shadow:0 5px 22px #26496c04;font-size:18px;line-height:1.85}.l1-reading>h1{font-size:30px;line-height:1.45;margin:10px 0 16px;color:#233e59}.l1-reading>.l1-label{font-size:14px;color:#7188a0;letter-spacing:0}.l1-reading>.l1-lead{font-size:19px;color:#60768a;line-height:1.85;margin-bottom:24px}.l1-storage:empty{display:none}.l1-storage{font-size:14px}.l1-art{border-radius:16px;background:#fffcf5;border-color:#e9e2d3}.l1-side-explanation{border-radius:16px;background:#f8fafc;border-color:#e5ebf2}.l1-side-explanation h2{font-size:19px}.l1-side-explanation .l1-note{background:#fff8e9;border-color:#ede3c9}.l1-quiz{border-radius:16px;padding:24px;background:#f4f8fd;border-color:#dfe9f5;margin:24px 0}.l1-quiz h3{font-size:20px;margin:10px 0 16px}.l1-bottom{border-top:1px solid #e7edf3;padding-top:22px;margin-top:28px}.l1-reading button,.l1-primary{border-radius:9px;font-size:16px}.l1-reading h2{font-size:23px}.l1-hero{border-radius:18px;padding:26px;border-color:#e0e9f1;background:linear-gradient(115deg,#edf5ff,#fff9e9)}.l1-hero h1{font-size:30px}.l1-hero p{font-size:18px}.l1-hero .l1-muted{font-size:14px;margin-top:16px}.l1-unit-grid a{border-radius:16px;padding:20px 125px 20px 20px;min-height:160px}.l1-unit-grid h2{font-size:21px}.l1-unit-grid p{font-size:16px}.l1-unit-grid a>span{font-size:13px}.l1-unit-grid img{height:125px;width:125px}.l1-note{font-size:17px}.l1-reading .l1-label{letter-spacing:0}.l1-output .l1-label{font-size:14px}.l1-code .l1-label{font-size:14px}.l1-output .l1-muted{font-size:16px}.reading-toolbar{background:#f7f9fc;border-color:#dfe7ef;border-radius:10px}.reading-toolbar .l2-trace-top{font-size:15px}.reading-toolbar .l2-trace-top span{font-size:14px}.reading-board .l3-input-record{background:#edf6f3}.l1-home{max-width:1160px}.welcome-hero{border-radius:24px}.welcome-paths>a{border-radius:18px}.welcome-paths h2{font-size:22px}.catalog-heading{margin:8px 0 28px}.catalog-heading h1{margin:10px 0}.catalog-heading p{font-size:18px;color:#72869a}.catalog-courses{display:grid;gap:18px;margin-bottom:32px}.catalog-courses>a{display:grid;grid-template-columns:160px 1fr;gap:28px;align-items:center;padding:22px;background:#fff;border:1px solid #e0e8f0;border-radius:18px}.catalog-art{border-radius:14px;background:#edf5ff}.catalog-art img{width:160px;height:160px;display:block}.catalog-courses>a:nth-child(2) .catalog-art{background:#fff6dd}.catalog-courses>a:nth-child(3) .catalog-art{background:#edf5ef}.catalog-courses h2{margin:5px 0;font-size:25px}.catalog-courses p{font-size:18px;color:#74879a}.catalog-courses strong{display:block;margin-top:12px;font-size:16px;color:#3474bd}footer{font-size:12px;color:#8a9aab;max-width:1540px;margin:auto;padding:22px 30px}
@media(max-width:1250px){:root{--shell-width:200px}.sidebar{padding:22px 12px}.brand img{width:158px}.l1-shell{grid-template-columns:1fr}.l1-menu{position:static;max-height:220px;border-bottom:1px solid #dfe7ef;padding-bottom:12px}.l1-reading{padding:24px}.l1-teaching{grid-template-columns:1fr}.workspace{margin-left:var(--shell-width)}}
@media(max-width:700px){:root{--shell-width:0px}.sidebar{position:static;width:100%;padding:12px 16px;border-bottom:1px solid #e1e8f0}.brand img{height:40px;width:132px;margin:0}.sidebar .product-name,.sidebar .nav-caption,.sidebar .sidebar-bottom{display:none}.sidebar nav{display:flex;overflow:auto;gap:5px;margin-top:10px}.sidebar nav>a{flex-shrink:0;min-height:42px;font-size:14px;padding:8px 12px}.sidebar nav .course-nav{padding:8px 12px}.sidebar nav .course-nav>span,.sidebar nav .course-nav small,.sidebar nav>a>span{display:none}.sidebar .course-nav b{font-size:14px}.sidebar nav .course-nav.active:before{display:none}.workspace{margin:0}.topbar{height:54px;padding:0 18px}.crumb-root,.crumb-divider{display:none}.search-shortcut{min-width:auto}.search-shortcut span,.search-shortcut kbd{display:none}.first-course-main{padding:16px!important}.l1-reading{padding:18px;border-radius:16px}.l1-reading>h1{font-size:26px}.l1-menu{max-height:none}.l1-menu:not([open]){padding-bottom:0}.l1-hero{padding:20px}.l1-hero h1{font-size:27px}.l1-unit-grid a{padding-right:100px}.l1-unit-grid img{width:100px;height:110px}.catalog-courses>a{grid-template-columns:90px 1fr;gap:15px;padding:16px}.catalog-art img{width:90px;height:110px}.catalog-courses h2{font-size:20px}.catalog-courses p{font-size:16px}.reading-board{grid-template-columns:1fr}.welcome-hero h1{font-size:28px}footer{padding:18px;font-size:11px}}
.record-grid{display:grid;gap:18px}.record-card{padding:26px;background:white;border:1px solid #e0e8f0;border-radius:18px}.record-card h2{font-size:24px;margin:6px 0 20px}.record-metrics{display:flex;gap:44px;margin-bottom:22px}.record-metrics>div{display:grid;gap:3px}.record-metrics strong{font-size:28px;color:#2c5d94}.record-metrics small{font-size:15px;color:#8394a7;font-weight:400}.record-metrics span{font-size:15px;color:#72879c}@media(max-width:700px){.record-metrics{gap:24px}.record-card{padding:20px}.record-card h2{font-size:22px}}

/* Keep the full lesson list and tools reachable as courses are added. */
@media(min-width:701px){.sidebar nav{flex:1;min-height:0;overflow-y:auto;overscroll-behavior:contain;scrollbar-width:thin}.sidebar nav>a,.sidebar .nav-tools-label{flex-shrink:0}.sidebar .brand,.sidebar .product-name,.sidebar>.nav-caption,.sidebar-bottom{flex-shrink:0}}