:root{--paper:#f5f7fc;--white:#fff;--ink:#202e48;--muted:#7c879d;--line:#e5e9f2;--blue:#5365db;--blue-soft:#eef0fe;--mint:#248575;--mint-soft:#eaf5f0;--amber:#bc8030;--amber-soft:#fff5e5;--serif:Georgia,'Songti SC','STSong',serif;--sans:-apple-system,BlinkMacSystemFont,'PingFang SC','Microsoft YaHei',sans-serif}
*{box-sizing:border-box}body{margin:0;background:var(--paper);color:var(--ink);font:14px/1.65 var(--sans)}button,input,a{-webkit-tap-highlight-color:transparent}button{font:inherit;cursor:pointer}button,a,input{outline-offset:5px}button:focus-visible,a:focus-visible,input:focus-visible{outline:3px solid var(--blue)}button{border:0}button:disabled{cursor:default;opacity:.5}a{color:inherit;text-decoration:none}.sidebar{width:244px;position:fixed;inset:0 auto 0 0;background:#fff;border-right:1px solid var(--line);padding:35px 22px 20px;display:flex;flex-direction:column;z-index:5}.brand{display:flex;align-items:center;gap:12px;margin:0 8px 42px;font-size:26px;font-weight:700;letter-spacing:2px}.brand-symbol{font:32px var(--serif);color:white;background:var(--ink);width:45px;height:48px;display:grid;place-items:center;border-radius:13px;transform:rotate(-5deg)}.brand-sub{display:block;font-size:10px;color:var(--muted);letter-spacing:1.6px;font-weight:400;margin-top:0}.catalog-label{font-size:10px;letter-spacing:1.5px;color:var(--muted);margin:0 12px 28px}.course-label{display:flex;justify-content:space-between;font-size:12px;margin:0 12px 14px}.course-label span{color:var(--muted)}.course-button{display:flex;width:100%;gap:12px;text-align:left;background:transparent;padding:16px 12px;color:var(--muted);border-radius:10px;margin:5px 0;align-items:center}.course-button.active{background:var(--blue-soft);color:var(--blue)}.course-number{font:18px var(--serif);width:23px}.course-button strong{font-size:13px;font-weight:600;display:block}.course-button small{display:block;font-size:10px;letter-spacing:.4px;margin-top:4px;opacity:.8}.course-dot{margin-left:auto;font-size:14px}.sidebar-note{margin:35px 12px 20px;padding-top:25px;border-top:1px solid var(--line)}.note-icon{display:block;font-size:31px;color:var(--blue);margin-bottom:8px}.sidebar-note strong{font-size:12px;font-weight:500}.sidebar-note p{font-size:11px;color:var(--muted);line-height:1.9}.progress-card{margin-top:auto;padding:18px 12px 8px;font-size:11px}.progress-card div{display:flex;justify-content:space-between}.progress-card strong{color:var(--blue);font-weight:500}.progress-card small{font-size:10px;color:var(--muted)}progress{width:100%;height:5px;border:0;margin:13px 0 6px;border-radius:8px;overflow:hidden;background:var(--line)}progress::-webkit-progress-bar{background:var(--line)}progress::-webkit-progress-value{background:var(--blue)}.text-button{background:transparent;color:var(--muted);font-size:11px;text-align:left;padding:9px 12px}.sidebar-footer{font-size:8px;letter-spacing:1px;display:flex;justify-content:space-between;color:var(--muted);margin:25px 12px 0}main{margin-left:244px}.topbar{height:77px;padding:0 44px;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;background:#ffffff88;gap:15px}.breadcrumb{font-size:11px;color:var(--muted)}.breadcrumb span{margin:0 14px;color:#bec6d5}.breadcrumb strong{color:var(--ink);font-weight:500}.toolbar{display:flex;align-items:center;gap:20px}.offline{font-size:10px;color:var(--muted);white-space:nowrap}.offline i{display:inline-block;width:5px;height:5px;background:var(--mint);border-radius:50%;margin-right:6px}.icon-button{background:transparent;color:var(--ink);padding:7px 0;font-size:16px}.icon-button span{font-size:11px;margin-left:4px}.content{max-width:1320px;margin:auto;padding:37px 44px 0}.intro{display:flex;justify-content:space-between;gap:16px;align-items:center}.eyebrow{font-size:10px;letter-spacing:2px;color:var(--blue);font-weight:600}h1{font-size:35px;font-weight:600;letter-spacing:1px;line-height:1.3;margin:11px 0 12px}.intro p{font-size:12px;color:var(--muted);margin:0}.guide-button{border:1px solid var(--line);border-radius:20px;padding:7px 12px;background:#fff;color:var(--muted);font-size:12px;white-space:nowrap}.guide-button span{margin-left:5px;font-size:10px}.lesson-meta{display:flex;gap:10px;margin:21px 0 30px;flex-wrap:wrap}.chip{font-size:10px;color:#68758e;display:inline-flex;align-items:center;gap:6px;background:#edf0f6;border:1px solid var(--line);border-radius:5px;padding:3px 9px}.chip.level{color:var(--mint);background:var(--mint-soft);border-color:#dcebe5}.stage-bar{display:flex;justify-content:space-between;align-items:center;border-bottom:1px solid #dfe4ef;margin-bottom:24px;gap:16px}#stage-tabs{display:flex;gap:27px}.stage-tab{background:transparent;color:var(--muted);padding:0 0 15px;border-bottom:2px solid transparent;margin-bottom:-1px;font-size:12px;white-space:nowrap}.stage-tab span{font:italic 13px var(--serif);margin-right:7px}.stage-tab.active{border-color:var(--blue);color:var(--blue);font-weight:600}.stage-hint{font-size:10px;color:var(--muted);padding-bottom:15px}.experiment{display:grid;grid-template-columns:minmax(0,1fr) 282px;background:var(--white);border:1px solid var(--line);border-radius:13px;overflow:hidden;min-height:415px}.canvas-panel{position:relative;display:flex;flex-direction:column;background-color:#fbfcff;background-image:radial-gradient(#d3dbeb .75px,transparent .75px);background-size:18px 18px;min-width:0}.canvas-header{padding:20px 24px;display:flex;align-items:center;justify-content:space-between;gap:10px}.canvas-header strong{font-size:12px;font-weight:500}.live-badge{font-size:9px;letter-spacing:.8px;border:1px solid #dfe6f4;background:#fff9;padding:3px 8px;border-radius:4px;color:var(--muted)}.canvas-panel svg{width:100%;height:270px;overflow:visible;touch-action:none;flex:1;min-height:230px}.canvas-caption{text-align:center;color:var(--muted);font-size:10px;padding:5px 12px 18px}.controls{border-left:1px solid var(--line);padding:23px 24px;display:flex;flex-direction:column}.control-top{display:flex;align-items:center;justify-content:space-between}.control-top h2{font-size:13px;margin:0;font-weight:600}.reset-exp{color:var(--muted);background:none;font-size:15px}.control-description{font-size:10px;color:var(--muted);margin:10px 0 20px}.slider-label{display:flex;justify-content:space-between;font-size:11px;align-items:center}.slider-label output{font:17px var(--serif);color:var(--blue)}input[type=range]{width:100%;accent-color:var(--blue);margin:17px 0 8px;cursor:ew-resize}.range-ends{display:flex;justify-content:space-between;color:var(--muted);font-size:9px;margin-bottom:21px}.parameter{display:flex;justify-content:space-between;color:var(--muted);font-size:11px;padding:8px 0}.parameter strong{font:16px var(--serif);color:var(--ink)}.metric{border-top:1px solid var(--line);margin-top:14px;padding-top:18px}.metric-label{font-size:10px;color:var(--muted)}.metric-number{font:38px var(--serif);margin:3px 0;color:var(--ink)}.metric-number small{font:10px var(--sans);color:var(--muted);margin-left:5px}.meter{height:4px;background:var(--blue-soft);margin:12px 0 8px;border-radius:5px;overflow:hidden}.meter div{height:100%;background:var(--blue);transition:width .12s}.metric-bottom{display:flex;justify-content:space-between;font-size:9px;color:var(--muted)}.secondary-button{border:1px solid #dce1f3;color:var(--blue);background:var(--blue-soft);border-radius:6px;padding:9px 14px;font-size:11px}.controls .secondary-button{width:100%;margin-top:20px}.observation{margin-top:17px;border:1px solid #dbe7e3;background:#f0f7f4;border-radius:9px;display:flex;align-items:center;gap:17px;padding:16px 21px;min-height:77px}.observation-icon{font:24px var(--serif);color:var(--mint)}.observation strong{font-size:11px;font-weight:600;color:var(--mint)}.observation p{font-size:11px;color:#5c7972;margin:2px 0}.observation .formula{margin-left:auto;font:22px var(--serif);color:var(--mint);white-space:nowrap}.lesson-footer{display:flex;justify-content:space-between;align-items:center;padding:23px 0;gap:20px}.lesson-footer>span{color:var(--muted);font-size:10px}.primary-button{display:inline-flex;align-items:center;justify-content:space-between;gap:25px;background:var(--blue);color:#fff;border-radius:7px;font-size:11px;padding:12px 19px;box-shadow:0 4px 9px #5365db14}.primary-button:hover{background:#4657c9}.bottom-note{display:flex;justify-content:space-between;border-top:1px solid var(--line);padding:17px 0;font-size:9px;color:#9aa4b7;gap:10px}.math{font-family:var(--serif)}.proof-layout{display:grid;grid-template-columns:minmax(0,1fr) 282px;gap:20px}.proof-main,.proof-aside,.quiz-card{background:white;border:1px solid var(--line);border-radius:12px;padding:26px}.proof-main h2{font-size:15px;margin:0 0 8px}.proof-main>p,.proof-aside p{font-size:11px;color:var(--muted);line-height:1.9}.theorem{padding:24px 10px;text-align:center;background:var(--blue-soft);border-radius:8px;margin:20px 0;color:var(--blue)}.theorem .math{font-size:29px;display:block}.theorem small{display:block;margin-top:8px;font-size:10px}.proof-step{display:flex;gap:13px;border-bottom:1px solid var(--line);padding:14px 0;animation:appear .25s ease}.step-index{background:var(--blue-soft);color:var(--blue);height:25px;width:25px;flex-shrink:0;text-align:center;border-radius:50%;font:italic 14px/25px var(--serif)}.proof-step strong{font-size:12px;font-weight:500}.proof-step p{font-size:11px;color:var(--muted);margin:5px 0}.proof-main .secondary-button{margin-top:20px}.proof-aside{align-self:start}.proof-aside h3{font-size:12px;margin:0 0 8px}.caution{background:var(--amber-soft);border-radius:8px;padding:14px;margin-top:22px}.caution strong{color:var(--amber);font-size:11px}.caution p{color:#92754d;margin:6px 0 0}.application{font-size:22px;color:var(--blue);margin:18px 0;line-height:1.8}.quiz-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:17px}.quiz-header h2{font-size:15px;margin:0}.quiz-header span{font-size:10px;color:var(--muted)}.questions{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}.quiz-card{padding:22px;display:flex;flex-direction:column}.question-tag{color:var(--blue);font-size:9px;letter-spacing:1px}.quiz-card h3{font-size:13px;font-weight:500;line-height:1.9;min-height:75px;margin:13px 0 16px}.options{display:grid;gap:8px}.option{border:1px solid var(--line);border-radius:6px;background:#fff;text-align:left;color:var(--ink);padding:10px;font-size:11px}.option span{color:var(--muted);font:12px var(--serif);margin-right:12px}.option:hover{border-color:#b5bee9;background:#fafaff}.option.selected{border-color:var(--blue);background:var(--blue-soft);color:var(--blue)}.option.correct{border-color:#80b9a8;background:var(--mint-soft);color:var(--mint)}.option.wrong{border-color:#d99c8b;background:#fff0eb;color:#ad5d45}.quiz-card .primary-button{margin-top:15px;justify-content:center;width:100%;padding:10px}.feedback{font-size:11px;line-height:1.8;margin:14px 0 0;padding:12px;border-radius:6px;background:var(--mint-soft);color:#497668}.feedback.retry{background:var(--amber-soft);color:#92754d}.feedback strong{display:block;margin-bottom:4px}.report-row{margin-top:18px;display:flex;justify-content:space-between;align-items:center;gap:15px;padding:17px 20px;background:#edf0f8;border-radius:9px;color:#69768f;font-size:11px}.report-row button{white-space:nowrap}.pigeon-controls{display:flex;gap:8px;margin-top:15px}.pigeon-controls button{flex:1;padding:8px 5px}.dots-legend{display:flex;gap:15px;justify-content:center;font-size:10px;color:var(--muted);padding-bottom:13px}.legend-dot{width:6px;height:6px;border-radius:50%;background:var(--blue);display:inline-block;margin-right:4px}dialog{width:min(590px,calc(100% - 30px));border:1px solid var(--line);border-radius:15px;padding:36px;color:var(--ink);box-shadow:0 25px 100px #15285322}dialog::backdrop{background:#19254155;backdrop-filter:blur(5px)}dialog h2{font-size:24px;line-height:1.5}dialog p,dialog li{font-size:12px;line-height:1.9}dialog li{padding:7px 0}dialog ol{padding-left:20px}dialog .close-dialog.icon-button{position:absolute;right:20px;top:10px;font-size:24px}.muted{color:var(--muted)}#toast{position:fixed;bottom:28px;left:50%;transform:translate(-50%,20px);background:var(--ink);color:#fff;padding:11px 20px;border-radius:8px;font-size:12px;opacity:0;transition:.2s;pointer-events:none;z-index:30}#toast.visible{opacity:1;transform:translate(-50%,0)}#print-handout{display:none}.presenting .sidebar{display:none}.presenting main{margin-left:0}.presenting .content{max-width:1400px}.presenting .experiment{min-height:480px}.presenting .canvas-panel svg{height:340px}@keyframes appear{from{opacity:0;transform:translateY(6px)}to{opacity:1;transform:translateY(0)}}@media(min-width:1550px){.content{padding-top:50px}.experiment{min-height:460px}.canvas-panel svg{height:315px}h1{font-size:41px}.lesson-meta{margin-bottom:34px}}@media(max-width:1150px){.sidebar{width:208px;padding-left:14px;padding-right:14px}main{margin-left:208px}.content{padding:28px 26px 0}.topbar{padding:0 26px}.experiment,.proof-layout{grid-template-columns:minmax(0,1fr) 250px}.controls{padding:20px}.stage-hint{display:none}.questions{gap:10px}.quiz-card{padding:17px}.toolbar{gap:13px}.observation .formula{font-size:18px}}@media(max-width:850px){.sidebar{position:static;width:100%;padding:15px 20px;border-right:0;border-bottom:1px solid var(--line)}.brand{margin:0;font-size:23px}.brand-symbol{height:38px;width:38px;font-size:26px}.brand-sub{font-size:9px}.sidebar nav{display:flex;margin-top:17px;gap:7px}.course-button{padding:10px 9px;gap:7px;margin:0}.course-number{font-size:15px;width:auto}.course-button strong{font-size:11px}.course-button small,.course-dot,.catalog-label,.course-label,.sidebar-note,.progress-card,.text-button,.sidebar-footer{display:none}main{margin-left:0}.topbar{height:57px;padding:0 22px}.content{padding:25px 22px 0}.toolbar{gap:13px}.offline{display:none}.experiment{grid-template-columns:minmax(0,1fr) 250px}h1{font-size:30px}.lesson-meta{margin:18px 0 26px}}@media(max-width:600px){.content{padding:23px 16px 0}.topbar{padding:0 16px}.breadcrumb{font-size:10px}.breadcrumb span{margin:0 6px}.icon-button span{font-size:10px}.toolbar{gap:12px}.brand{font-size:21px}.brand-sub{letter-spacing:1px}.course-button strong{font-size:10px}.course-button{padding:10px 6px;gap:6px}.course-number{font-size:12px}.sidebar{padding:14px 16px}.guide-button span{display:none}.guide-button{padding:4px 10px}h1{font-size:27px}.intro p{font-size:11px}.eyebrow{font-size:8px}.lesson-meta{gap:6px}.chip{font-size:9px}.stage-tab{font-size:11px}#stage-tabs{gap:23px}.experiment{grid-template-columns:1fr}.canvas-panel svg{height:240px;flex:none}.controls{border-left:0;border-top:1px solid var(--line);padding:20px}.control-description{margin-bottom:13px}.range-ends{margin-bottom:9px}.metric{margin-top:10px;padding-top:12px}.metric-number{font-size:32px}.controls .secondary-button{margin-top:12px}.observation{align-items:flex-start;padding:14px;gap:11px}.observation .formula{display:none}.lesson-footer{gap:12px}.lesson-footer>span{max-width:55%;font-size:9px}.primary-button{gap:12px;padding:11px 13px}.proof-layout,.questions{grid-template-columns:1fr}.quiz-card h3{min-height:0}.report-row{align-items:flex-start;flex-direction:column}.bottom-note{font-size:8px}.proof-main,.proof-aside{padding:20px}.theorem .math{font-size:24px}.presenting .canvas-panel svg{height:270px}.presenting .experiment{min-height:0}}@media(prefers-reduced-motion:reduce){*,*::before,*::after{animation:none!important;transition:none!important;scroll-behavior:auto!important}}@media print{body{background:white;color:#17223b;font-size:11pt}.sidebar,main,dialog,#toast{display:none!important}#print-handout{display:block;max-width:180mm;margin:0 auto}#print-handout h1{font-size:26pt}#print-handout h2{font-size:20pt}#print-handout h3{font-size:13pt}#print-handout .print-lesson{break-before:page}#print-handout li{margin-bottom:8pt}#print-handout p{line-height:1.8}#print-handout .answer-key{border-top:1px solid #ccc;padding-top:15pt}#print-handout .print-formula{font:20pt var(--serif);padding:16pt;background:#f1f3fb}.print-lesson{page-break-inside:avoid}@page{size:A4;margin:18mm}}