:root{--ink:#17253b;--muted:#647389;--line:#dde5ef;--blue:#245ec8;--orange:#bd5328;--green:#337764;--paper:#fff;--surface:#f5f7fb;--ease:cubic-bezier(.23,1,.32,1)}
*{box-sizing:border-box}body{margin:0;background:var(--surface);color:var(--ink);font-family:-apple-system,BlinkMacSystemFont,"HarmonyOS Sans SC","Microsoft YaHei","Noto Sans CJK SC",sans-serif;-webkit-font-smoothing:antialiased}a{color:inherit;text-decoration:none}button,input{font:inherit}button{cursor:pointer;touch-action:manipulation}button,a,input{-webkit-tap-highlight-color:transparent}button:disabled{cursor:default;opacity:.38}button:focus-visible,a:focus-visible,input:focus-visible,summary:focus-visible{outline:3px solid #e9a431;outline-offset:4px}[hidden]{display:none!important}.pp-header{display:flex;align-items:center;justify-content:space-between;gap:16px;min-height:76px;border-bottom:1px solid var(--line);padding:0 40px}.pp-brand{display:flex;align-items:center;gap:12px;white-space:nowrap}.pp-brand svg{width:36px;height:36px;fill:none;stroke:var(--blue);stroke-width:2.3}.pp-brand svg path+path{stroke:var(--orange)}.pp-brand strong{font-size:19px}.pp-brand>span{border-left:1px solid #c5cedb;padding-left:14px;font-size:14px;color:var(--muted);margin-left:3px}.header-tools{display:flex;align-items:center;gap:8px}.term-label{font-size:13px;color:var(--muted)}.primary-button,.soft-button,.icon-control{display:inline-flex;align-items:center;justify-content:center;gap:14px;min-height:46px;padding:10px 17px;border-radius:7px;font-weight:550;font-size:14px;border:1px solid var(--line);background:white;color:var(--ink)}.primary-button{color:white;background:var(--blue);border-color:var(--blue)}.primary-button:active,.soft-button:active{transform:translateY(1px)}.icon-control{min-width:46px;padding:6px;border-color:transparent;background:transparent;font-size:29px;line-height:1}.eyebrow{font-size:12px;letter-spacing:.05em;color:var(--muted)}.library-main{max-width:1350px;margin:auto;padding:0 40px 55px}.library-hero{display:flex;justify-content:space-between;align-items:flex-end;gap:30px;padding:55px 0 37px}.library-hero h1{font-size:clamp(35px,4vw,54px);font-weight:650;letter-spacing:-.055em;line-height:1.25;margin:12px 0 15px}.library-hero h1 span{color:var(--blue)}.library-hero p{color:var(--muted);font-size:16px;line-height:1.85;margin:0}.hero-stamp{display:flex;flex-direction:column;align-items:flex-end;padding-bottom:5px}.hero-stamp strong{font-family:Georgia,serif;font-size:52px;font-weight:400;line-height:1;color:var(--blue)}.hero-stamp span{font-size:12px;color:var(--muted);margin-top:8px}.books-nav{display:flex;gap:32px;border-bottom:1px solid var(--line);margin-bottom:27px}.book-tab{display:flex;align-items:center;gap:12px;border:0;border-bottom:3px solid transparent;background:transparent;color:var(--muted);font-size:17px;padding:16px 1px;min-height:59px}.book-tab[aria-selected=true]{color:var(--blue);border-bottom-color:var(--blue);font-weight:650}.book-tab small{font-size:11px;background:#e7edf7;padding:3px 7px;border-radius:4px;color:var(--muted)}.book-tab[aria-selected=true] small{background:#e8effd;color:var(--blue)}.book-description{display:flex;justify-content:space-between;align-items:center;gap:15px;margin:0 0 18px}.book-description h2{font-size:18px;font-weight:650;margin:0}.book-description p{font-size:13px;color:var(--muted);margin:0}.lecture-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:15px}.lecture-card{display:flex;flex-direction:column;position:relative;background:white;border:1px solid var(--line);border-radius:10px;min-height:165px;padding:20px;transition:border-color .16s,box-shadow .16s}.lecture-card.available{border-color:#c9d8ef}.lecture-card.unavailable{background:#f8f9fc;color:#758195}.card-meta{display:flex;justify-content:space-between;align-items:center}.card-number{font:23px Georgia,serif;color:#8b9bb3}.available .card-number{color:var(--blue)}.card-status{font-size:11px;color:var(--muted)}.available .card-status{color:var(--green)}.lecture-card h3{font-size:18px;font-weight:600;line-height:1.55;margin:17px 0 16px}.card-bottom{display:flex;align-items:center;justify-content:space-between;font-size:12px;color:var(--muted);margin-top:auto}.card-arrow{font-size:20px;color:var(--blue)}.examples-strip{margin-top:40px;border-top:1px solid var(--line);padding-top:23px;display:flex;gap:17px;align-items:center;flex-wrap:wrap;font-size:14px}.examples-strip>span{color:var(--muted);margin-right:10px}.examples-strip a{border-bottom:1px solid #b8c9e5;padding:6px 0;color:var(--blue)}.library-footer{max-width:1350px;margin:auto;border-top:1px solid var(--line);padding:18px 40px 25px;display:flex;justify-content:space-between;font-size:12px;color:var(--muted)}
.classroom-page{height:100svh;min-height:600px;display:flex;flex-direction:column}.classroom-page .pp-header{min-height:66px;flex-shrink:0}.classroom{display:flex;flex:1;min-height:0;flex-direction:column;padding:0 32px;max-width:1800px;width:100%;margin:auto}.lecture-bar{display:flex;align-items:center;justify-content:space-between;gap:20px;padding:15px 0 17px;flex-shrink:0}.lecture-bar h1{font-size:22px;font-weight:600;margin:5px 0 0;letter-spacing:-.025em}.source-location{color:var(--muted);font-size:12px;white-space:nowrap}.class-stage{display:grid;grid-template-columns:minmax(315px,36%) minmax(0,1fr);gap:26px;min-height:0;flex:1}.teaching-panel{min-height:0;overflow-y:auto;overscroll-behavior:contain;scrollbar-width:thin;display:flex;flex-direction:column;padding:13px 12px 18px 0}.item-heading{display:flex;align-items:center;justify-content:space-between;font-size:13px;color:var(--muted);gap:12px}.item-heading>span:first-child{font-weight:650;color:var(--blue)}.item-heading>span:last-child{font:16px Georgia,serif}.teaching-panel h2{font-size:clamp(25px,2.25vw,35px);letter-spacing:-.035em;line-height:1.4;margin:21px 0;max-width:15em}.teaching-body{font-size:clamp(17px,1.4vw,22px);line-height:1.85}.teaching-body p{margin:0 0 15px}.teaching-body ul,.teaching-body ol{padding-left:1.35em;margin:14px 0}.teaching-body li{margin:7px 0}.teaching-caption{margin-top:auto;padding:20px 0 0;color:var(--muted);font-size:14px;line-height:1.75;border-top:1px solid transparent}.visual-panel{background:white;border:1px solid var(--line);border-radius:12px;overflow:hidden;min-height:0;display:flex;flex-direction:column}.visual-heading{padding:20px 23px 9px;display:flex;gap:14px;align-items:center;justify-content:space-between;font-size:13px;color:var(--muted)}.visual-heading>span:last-child{font-size:11px;white-space:nowrap;color:var(--green)}.visual-heading>span.pending{color:var(--orange);background:#fcf0e9;padding:4px 8px;border-radius:4px}.scene{flex:1 1 0;min-height:0;display:flex;align-items:center;justify-content:center;overflow:hidden;padding:8px 12px 14px}.scene>svg{width:100%;height:100%;display:block;overflow:visible}.scene text{paint-order:stroke;stroke:white;stroke-width:2px;stroke-linejoin:round}.scene .geo-line{vector-effect:non-scaling-stroke;stroke-linecap:round;stroke-linejoin:round}.scene .geo-label{font:italic 25px Georgia,serif;fill:var(--ink)}.source-preview{width:100%;height:100%;display:flex;justify-content:center}.source-preview img{max-width:100%;max-height:100%;object-fit:contain}.scene-note{font-size:13px;color:var(--orange);padding:7px 22px 14px;line-height:1.6}.scene-error{padding:20px;line-height:1.8;color:var(--muted)}.motion-controls{padding:12px 18px;background:#f8faff;border-top:1px solid var(--line);flex-shrink:0}.motion-row{display:flex;gap:12px;align-items:center;font-size:13px}.motion-row input{flex:1;min-width:35px;height:44px;accent-color:var(--blue);touch-action:pan-y}.motion-row output{font-variant-numeric:tabular-nums;color:var(--blue);min-width:80px;text-align:right}.motion-row label{white-space:nowrap;color:var(--muted)}.motion-row .soft-button{min-width:66px;color:var(--blue)}.event-marks{display:flex;flex-wrap:wrap;gap:6px;margin-bottom:6px}.event-marks:empty{display:none}.event-mark{font-size:12px;min-height:36px;border:1px solid #d4def0;border-radius:5px;background:white;color:var(--muted);padding:7px 9px}.event-mark[aria-pressed=true]{border-color:var(--blue);background:#eaf0fd;color:var(--blue)}.class-footer{display:flex;align-items:center;justify-content:space-between;gap:24px;margin-top:18px;min-height:82px;border-top:1px solid var(--line);padding:13px 0 max(15px,env(safe-area-inset-bottom));flex-shrink:0}.whole-progress{font-size:12px;color:var(--muted);width:210px}.progress-track{height:3px;background:#dce3ef;margin-top:11px;overflow:hidden}.progress-track>span{display:block;height:100%;background:var(--blue);transition:width .16s ease-out}.lesson-actions{display:flex;gap:10px;align-items:center}.lesson-actions>button:first-child{border-color:transparent;background:transparent;color:var(--muted);margin-right:9px}.navigation-button{min-width:118px;min-height:51px;font-size:15px}.load-state{margin:12vh auto;padding:25px;color:var(--muted);line-height:1.9}.load-state h1{color:var(--ink);font-size:26px}.load-state a{margin-top:15px}
.math{font-family:"Cambria Math","STIX Two Math","Times New Roman",serif;letter-spacing:.01em}.blue{color:var(--blue)}.orange{color:var(--orange)}.green{color:var(--green)}.keyword{color:var(--blue);background:#eaf0fd;border-radius:3px;padding:1px 4px}.keyword.orange{color:var(--orange);background:#fcf0e9}.proof-block{border-left:3px solid var(--blue);padding:6px 0 6px 17px;margin:18px 0}.proof-block p{margin:5px 0}.conclusion{font-weight:650;color:var(--blue);font-size:1.1em;line-height:1.7;margin:18px 0}.subtle,.muted{font-size:.83em;color:var(--muted)}.math-line{display:block;margin:10px 0;line-height:1.75}.fraction{display:inline-flex;vertical-align:middle;flex-direction:column;text-align:center;line-height:1.25;margin:0 .16em;font-family:"Cambria Math","Times New Roman",serif}.fraction>span{padding:2px 5px}.fraction>span:first-child{border-bottom:1px solid currentColor}.teaching-body table{border-collapse:collapse;max-width:100%;width:100%;font-size:.8em;line-height:1.6;margin:14px 0}.teaching-body th,.teaching-body td{border:1px solid var(--line);padding:7px 8px;text-align:left}.teaching-body th{font-weight:600;background:#edf2fa}.pending-note,.boundary-note{border-left:3px solid var(--orange);padding:12px 15px;background:#fcf4ee;line-height:1.8}.teaching-body .pending-note{font-size:.9em}dialog{border:1px solid var(--line);border-radius:13px;color:var(--ink);padding:23px 26px;max-width:820px;width:calc(100% - 32px);max-height:90svh;box-shadow:0 20px 90px #17253b26}dialog::backdrop{background:#13253b80}.dialog-top{display:flex;align-items:flex-start;justify-content:space-between;gap:20px;margin-bottom:20px}.dialog-top h2{font-size:24px;line-height:1.45;margin:5px 0}.dialog-top>button{flex-shrink:0;border:0}.toc-dialog{max-width:680px}.toc-item{display:grid;grid-template-columns:100px 1fr;gap:5px 12px;text-align:left;width:100%;background:white;border:1px solid var(--line);border-radius:8px;padding:16px;margin:10px 0;min-height:70px}.toc-item>span{font-size:13px;color:var(--blue);grid-row:span 2;align-self:center}.toc-item strong{font-size:16px;font-weight:550;line-height:1.5}.toc-item small{font-size:12px;color:var(--muted)}.toc-item[aria-current=step]{border-color:var(--blue);background:#f5f8ff}.original-text{font-size:18px;line-height:1.9;overflow-wrap:anywhere}.original-text p{margin:0 0 16px}.source-dialog details{border-top:1px solid var(--line);margin-top:24px;padding-top:13px}.source-dialog summary{cursor:pointer;padding:12px 0;color:var(--blue);min-height:44px}.source-dialog figure{margin:18px 0}.source-dialog img{display:block;width:100%;height:auto;border:1px solid var(--line)}.source-dialog figcaption{padding:8px;color:var(--muted);font-size:12px;text-align:center}.pp-toast{position:fixed;left:50%;bottom:100px;transform:translateX(-50%);z-index:20;max-width:90%;background:var(--ink);color:white;padding:13px 20px;border-radius:8px;font-size:14px}
@media(hover:hover) and (pointer:fine){.primary-button:hover{background:#184cad}.soft-button:hover,.icon-control:hover{background:#edf2fa}.lecture-card.available:hover{border-color:var(--blue);box-shadow:0 6px 22px #245ec80a}.event-mark:hover{border-color:#7a9bd5;color:var(--blue)}}
@media(min-width:1550px){.class-stage{grid-template-columns:470px 1fr;gap:38px}.classroom{padding:0 45px}.teaching-body{font-size:23px}.teaching-panel h2{font-size:36px}}
@media(max-width:1100px){.pp-header{padding:0 24px}.library-main{padding:0 24px 40px}.library-hero{padding:40px 0 30px}.lecture-grid{grid-template-columns:repeat(3,minmax(0,1fr))}.classroom{padding:0 22px}.class-stage{grid-template-columns:minmax(275px,38%) minmax(0,1fr);gap:19px}.teaching-body{font-size:17px}.teaching-panel h2{font-size:27px}.visual-heading{padding:16px 15px 7px}.motion-controls{padding:10px 12px}.event-mark{font-size:11px}.lecture-bar h1{font-size:20px}.motion-row{gap:8px}.motion-row output{min-width:68px}.whole-progress{width:170px}}
@media(max-width:760px),(max-width:950px) and (orientation:portrait){.pp-header{padding:0 17px;min-height:65px}.pp-brand{gap:8px}.pp-brand svg{width:30px}.pp-brand strong{font-size:17px}.pp-brand>span{display:none}.term-label{display:none}.header-tools{gap:2px}.header-tools .soft-button{font-size:12px;min-height:44px;padding:9px}.header-tools .icon-control{min-width:39px}.library-main{padding:0 19px 32px}.library-hero{padding:33px 0 25px;gap:12px}.library-hero h1{font-size:36px}.library-hero p{font-size:13px}.hero-stamp strong{font-size:37px}.hero-stamp span{font-size:10px}.books-nav{gap:23px;margin-bottom:22px}.book-tab{font-size:16px;gap:8px}.book-description{align-items:flex-start}.book-description h2{font-size:16px}.book-description p{font-size:12px;max-width:12em;line-height:1.7;text-align:right}.lecture-grid{grid-template-columns:repeat(2,minmax(0,1fr));gap:11px}.lecture-card{padding:16px;min-height:158px}.lecture-card h3{font-size:16px;margin:14px 0}.card-number{font-size:21px}.card-bottom{font-size:11px}.examples-strip{gap:10px 16px;margin-top:30px;font-size:13px}.examples-strip>span{width:100%}.library-footer{padding:17px 19px;font-size:11px;gap:15px}.classroom-page{height:auto;min-height:100svh}.classroom{padding:0 17px}.lecture-bar{padding:17px 0;gap:10px}.lecture-bar h1{font-size:20px}.lecture-bar .eyebrow{font-size:11px}.source-location{font-size:10px;align-self:flex-start;margin-top:3px}.class-stage{display:flex;flex-direction:column;gap:13px}.teaching-panel{overflow:visible;padding:2px 0 5px}.teaching-panel h2{font-size:28px;max-width:100%;margin:16px 0}.teaching-body{font-size:18px}.teaching-caption{padding:5px 0 0;font-size:13px;margin:5px 0}.scene{height:340px;min-height:300px;flex-basis:auto;padding:8px}.visual-heading{font-size:12px}.scene-note{font-size:12px;padding:7px 14px}.motion-controls{padding:10px 12px}.event-mark{min-height:40px}.class-footer{position:sticky;bottom:0;z-index:4;background:#f5f7bff2;background:rgba(245,247,251,.97);margin-top:15px;min-height:79px;gap:0}.whole-progress{display:none}.lesson-actions{width:100%;gap:8px}.lesson-actions>button:first-child{padding:9px;font-size:12px;min-width:50px;margin:0}.navigation-button{flex:1;min-width:0;min-height:50px;padding:10px 13px;font-size:14px}.motion-row label{display:none}.toc-item{grid-template-columns:72px 1fr}.toc-item strong{font-size:15px}.toc-item>span{font-size:12px}dialog{padding:19px 18px}.original-text{font-size:17px}.dialog-top h2{font-size:21px}.dialog-top{gap:10px}}
@media(min-width:761px) and (max-height:740px){.classroom-page .pp-header{min-height:58px}.lecture-bar{padding:10px 0 12px}.lecture-bar h1{font-size:19px}.class-footer{min-height:73px;margin-top:13px}.teaching-panel h2{font-size:26px;margin:16px 0}.teaching-body{font-size:17px}.motion-controls{padding:7px 12px}.event-mark{min-height:32px;padding:5px 8px}}
@media(prefers-reduced-motion:reduce){*,*:before,*:after{animation-duration:.01ms!important;animation-delay:0ms!important;transition-duration:.01ms!important;scroll-behavior:auto!important}}
@media(max-width:760px),(max-width:950px) and (orientation:portrait){.library-hero h1 span{white-space:nowrap}.hero-stamp{display:none}.event-mark{min-height:44px}}