:root{--ink:#203b4a;--muted:#637882;--teal:#147d7a;--paper:#f6f8f5;--line:#dbe4df;--gold:#e7aa53;font-family:'Microsoft YaHei','PingFang SC',system-ui,sans-serif;color:var(--ink);background:var(--paper);font-synthesis:none}*{box-sizing:border-box}body{margin:0}a{color:var(--teal);text-decoration:none}button,select,input{font:inherit}button,.button{display:inline-flex;align-items:center;justify-content:center;gap:20px;border:0;border-radius:9px;background:var(--teal);color:white;padding:12px 20px;cursor:pointer;font-weight:600;line-height:1.5}button:hover,.button:hover{filter:brightness(.94)}button:disabled{cursor:default;opacity:.5}.secondary{background:#edf2ef;color:var(--ink);border:1px solid var(--line)}a:focus-visible,button:focus-visible,input:focus-visible,summary:focus-visible,select:focus-visible{outline:3px solid #e7aa53;outline-offset:4px}[hidden]{display:none!important}.site-header{max-width:1320px;margin:auto;padding:27px 38px;display:flex;align-items:center;justify-content:space-between;border-bottom:1px solid var(--line);gap:24px}.brand{font-size:25px;letter-spacing:-1px;font-weight:800;color:var(--ink);white-space:nowrap}.brand>span{color:var(--teal)}.brand small{display:block;font-size:8px;letter-spacing:2px;margin-top:5px}.site-header nav{display:flex;gap:36px;font-size:14px}.site-header nav a{color:var(--ink)}.sample-pill{font-size:12px;padding:8px 13px;background:#e7eee7;border-radius:30px;color:#456957}main{max-width:1244px;margin:auto;padding:0 32px 60px}.hero{display:grid;grid-template-columns:1.05fr 1fr;gap:60px;align-items:center;padding:65px 0 54px}.eyebrow{font-size:11px;font-weight:700;letter-spacing:2px;color:var(--teal)}h1{font-size:56px;line-height:1.2;letter-spacing:-2px;margin:23px 0}h1>span{color:var(--teal)}p{line-height:1.8}.hero p{color:var(--muted);font-size:16px;margin:24px 0 30px}.hero-note{display:block;font-size:11px;color:var(--muted);margin-top:14px}.hero-art{position:relative;min-height:335px;border:1px solid #d7e4dc;background-color:#eaf1e8;background-image:linear-gradient(#dce6da70 1px,transparent 1px),linear-gradient(90deg,#dce6da70 1px,transparent 1px);background-size:26px 26px;border-radius:28px;padding:28px 34px;transform:rotate(-2deg);box-shadow:12px 15px 0 #e2e9df80}.art-tag{font-size:11px;color:var(--teal);background:#fff;padding:7px 12px;border-radius:20px}.art-formula{font-size:58px;font-weight:600;text-align:center;margin:25px 0;color:#285b53}.art-formula span{color:#83a38f}.art-line{display:flex;position:relative;justify-content:space-between;border-top:2px solid #658677;margin-top:37px;padding-top:14px}.art-line b{font-size:13px;font-weight:400;position:relative}.art-line b:before{content:'';height:8px;position:absolute;top:-20px;left:40%;border-left:2px solid #658677}.art-line i{position:absolute;width:50%;height:5px;background:var(--gold);top:-10px;left:0}.hero-art p{text-align:center;font-size:13px;margin:22px 0 7px;color:#547368}.art-caption{display:block;font-size:8px;letter-spacing:3px;text-align:center;color:#7b9486}.stats{display:grid;grid-template-columns:repeat(4,1fr);background:#fff;border:1px solid var(--line);border-radius:14px;padding:23px 16px}.stats>div{padding:0 25px;border-right:1px solid var(--line)}.stats>div:last-child{border:0}.stats strong{display:block;font-size:29px;font-weight:600}.stats small{font-size:15px;color:var(--muted)}.stats span{font-size:12px;color:var(--muted)}.course-section{margin-top:55px}.section-title{display:flex;justify-content:space-between;align-items:end;margin-bottom:25px}.section-title h2{font-size:25px;margin:10px 0 0}.section-title>span{font-size:12px;color:var(--muted)}.course-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px}.course-card{position:relative;background:#fff;border:1px solid var(--line);border-radius:15px;padding:28px;overflow:hidden}.course-number{position:absolute;right:22px;top:14px;font-size:39px;font-weight:700;color:#e3ebe6}.course-card .eyebrow{font-size:10px;letter-spacing:1px}.course-card h3{font-size:26px;margin:19px 0 5px}.course-card p{font-size:13px;color:var(--muted)}.mini-visual{padding:25px 0;background:#f2f6ef;border-radius:10px;margin:24px 0;text-align:center;font-size:25px;letter-spacing:3px;color:#4c7464}.course-card:nth-child(2) .mini-visual{background:#faf3e7;color:#a87b36}.course-card:nth-child(3) .mini-visual{background:#edf2f9;color:#657997}.actions{display:flex;gap:12px;align-items:center;flex-wrap:wrap}.course-card .actions{font-size:12px;justify-content:space-between}.course-card .button{padding:10px 15px}.fine{font-size:12px!important;color:var(--muted);line-height:1.7}.roadmap{margin-top:40px;background:#edf1eb;border-radius:14px;padding:24px 28px}.roadmap h2{font-size:18px;margin:0}.roadmap p{font-size:12px;color:var(--muted)}.chapter-row{display:grid;grid-template-columns:repeat(4,1fr);gap:20px;font-size:12px}.chapter-row b{display:block;font-size:10px;font-weight:400;color:var(--muted);margin-top:8px}footer{max-width:1244px;margin:auto;border-top:1px solid var(--line);padding:24px 32px;display:flex;justify-content:space-between;font-size:11px;color:var(--muted)}.page-heading{padding:48px 0 28px}.page-heading h1{font-size:36px}.page-heading p{color:var(--muted);font-size:14px}.practice-layout{display:grid;grid-template-columns:230px 1fr;gap:28px}.practice-layout aside{padding:20px;background:#eaf0e9;border-radius:12px;align-self:start}.practice-layout aside a{display:block;padding:12px 0;font-size:14px}.practice-panel{background:white;border:1px solid var(--line);border-radius:14px;padding:30px}.practice-toolbar{display:flex;gap:20px;align-items:center;border-bottom:1px solid var(--line);padding-bottom:20px;margin-bottom:28px;font-size:13px}.practice-toolbar select{padding:7px;border:1px solid var(--line);border-radius:6px}.practice-toolbar #counter{margin-left:auto}.exercise h3{font-size:24px;line-height:1.6}.options{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin:23px 0}.option{text-align:left;justify-content:flex-start;background:#f8faf7;border:1px solid var(--line);color:var(--ink);font-weight:400}.option span{color:var(--teal);font-weight:600}.option:disabled{opacity:1}.option.correct{background:#d9f1e3;border-color:#378869}.option.wrong{background:#fff0e8;border-color:#d28963}.exercise .actions button{font-size:12px}.feedback{font-size:14px;color:var(--teal)}.solution{padding:16px 20px;background:#eff5ed;border-radius:10px;font-size:14px}.solution p{margin:8px 0}.hint-text{font-size:14px;background:#fff7df;padding:10px 16px}.question-nav{justify-content:space-between;border-top:1px solid var(--line);padding-top:22px;margin-top:25px}.mistake-list{margin-top:25px;display:grid;gap:18px}.mistake-card{padding:25px;background:white;border:1px solid var(--line);border-radius:12px}.mistake-card h3{font-size:20px}.mistake-card p{font-size:14px}.status{color:#af7330;font-size:12px}.status.done{color:var(--teal)}details summary{cursor:pointer;color:var(--teal);font-size:14px}.empty{padding:35px;text-align:center;color:var(--muted)}.line-visual svg{width:100%;overflow:visible}.point,.distance{transition:all .35s ease}input[type=range]{accent-color:var(--teal);width:50%;vertical-align:middle}.number-presets{display:inline-flex;gap:8px;margin-left:15px}.number-presets button{padding:5px 12px}.visual-readout{color:var(--teal)}.balance{position:relative;max-width:800px;margin:25px auto 5px;padding-top:18px}.beam{height:7px;background:#72998c;border-radius:5px;margin:0 10%}.pans{display:flex;align-items:center;justify-content:space-around;gap:20px}.pan{flex:1;border-bottom:5px solid #72998c;background:#eef4e9;border-radius:0 0 30px 30px;padding:20px 8px;color:#507961;transition:background .4s;white-space:nowrap}.solved .pan{background:#deeee4}.stand{text-align:center;color:#72998c;font-size:50px;line-height:1}.equation-readout{font-weight:600;font-size:28px!important;color:var(--teal)}@media(max-width:900px){.hero{gap:25px}.hero h1{font-size:44px}.hero-art{padding:25px 20px}.course-grid{gap:12px}.course-card{padding:20px}.course-card .actions{gap:10px}.brand small{display:none}.sample-pill{display:none}.practice-layout{grid-template-columns:180px 1fr}.chapter-row{grid-template-columns:1fr 1fr}}@media(max-width:620px){.site-header{padding:18px 20px}.site-header nav{gap:18px}.brand{font-size:22px}main{padding:0 20px 30px}.hero{grid-template-columns:1fr;padding:32px 0;gap:25px}.hero h1{font-size:43px}.hero-art{min-height:270px}.art-formula{font-size:45px;margin:20px 0}.stats{grid-template-columns:1fr 1fr;gap:20px}.stats>div:nth-child(2){border:0}.stats>div{padding:0 16px}.course-grid{grid-template-columns:1fr}.section-title{display:block}.section-title>span{display:block;margin-top:10px}.practice-layout{grid-template-columns:1fr}.practice-layout aside{display:flex;gap:14px;flex-wrap:wrap;padding:16px}.practice-layout aside h3,.practice-layout aside .fine{display:none}.practice-layout aside a{padding:0;font-size:12px}.practice-panel{padding:20px}.options{grid-template-columns:1fr}.practice-toolbar{gap:10px}.page-heading h1{font-size:30px}footer{gap:20px}.chapter-row{gap:20px}}
@media(prefers-reduced-motion:reduce){*{transition:none!important;animation:none!important}}
.numeric-form{display:flex;flex-wrap:wrap;gap:14px;align-items:center;margin:22px 0}.numeric-form input,.exam-answer{padding:12px;border:1px solid #b9cbc1;border-radius:8px;max-width:100%;font-size:17px}.input-error{font-size:13px;color:#a34725}.explorer-controls{display:flex;gap:20px;flex-wrap:wrap}.explorer-controls label{font-size:18px}.explorer-controls input{width:150px}.explorer-controls output{font-weight:700;color:var(--teal)}.explorer-stage>svg,.shape-view svg{max-height:240px;width:100%}.explorer-stage .formula,.formula{font-size:30px;font-weight:600;color:var(--teal)}.compare-box{display:grid;grid-template-columns:1fr 1fr;gap:18px;margin:20px 0}.compare-box>div,.equal-pans{border:2px solid #90b3a3;padding:16px;border-radius:14px;background:#fff;text-align:center}.tile-row{display:flex;gap:8px;flex-wrap:wrap;margin:20px 0}.math-tile{display:inline-block;padding:12px;background:#dcebe4;border-radius:5px;font-size:20px}.filled{background:#81b8a0}.order-flow{padding:22px;background:#dcebe4;border-radius:12px}.term-cards,.term-bins{display:flex;gap:14px;margin:24px 0;flex-wrap:wrap}.term-bins button{min-width:150px;min-height:60px}.equal-pans{display:flex;justify-content:space-around}.cube-scene{height:230px;perspective:900px;display:grid;place-items:center;overflow:hidden}.net{position:relative;width:65px;height:65px;transform:rotateX(35deg) rotateZ(-12deg);transform-style:preserve-3d}.face{width:65px;height:65px;display:grid;place-items:center;background:#bcdfca;border:2px solid #468775;font-size:20px;backface-visibility:visible}.hinge{position:absolute;width:65px;height:65px;transform-style:preserve-3d;transition:none}.hinge.top{top:-65px;transform-origin:bottom;transform:rotateX(calc(-1 * var(--fold)))}.hinge.bottom{top:65px;transform-origin:top;transform:rotateX(var(--fold))}.hinge.left{left:-65px;top:0;transform-origin:right;transform:rotateY(var(--fold))}.hinge.right{left:65px;top:0;transform-origin:left;transform:rotateY(calc(-1 * var(--fold)))}.hinge.back{left:65px;top:0;transform-origin:left;transform:rotateY(calc(-1 * var(--fold)))}.chapter-tabs{display:flex;gap:12px;flex-wrap:wrap;margin:25px 0}.chapter-tabs a{border:1px solid var(--line);padding:10px 15px;border-radius:9px;background:white}.course-grid.full{grid-template-columns:repeat(3,1fr)}.exam-card{background:white;border:1px solid var(--line);border-radius:12px;padding:22px;margin:15px 0}.exam-card label{display:block;padding:9px;cursor:pointer}.exam-card input[type=radio]{margin-right:10px}.exam-result{background:#e1eee3;border-radius:12px;padding:25px}.topic-select{width:100%;padding:10px;border:1px solid var(--line);border-radius:6px;margin:10px 0}.table-scroll{overflow:auto}table{border-collapse:collapse;width:100%;font-size:14px}td,th{text-align:left;border-bottom:1px solid var(--line);padding:12px}.chapter-card{padding:22px;background:white;border:1px solid var(--line);border-radius:14px}.progress-bar{height:5px;background:#e8eeea;margin:15px 0}.progress-bar>i{display:block;height:100%;background:var(--teal)}.exam-actions{position:sticky;bottom:0;background:#f6f8f5eF;padding:15px;display:flex;gap:15px;z-index:2}.foundation-lesson{background:#fff;padding:25px;border-radius:15px;margin:22px 0}.diagnostic-badge{font-size:12px;color:var(--muted)}@media(max-width:900px){.course-grid.full{grid-template-columns:1fr 1fr}}@media(max-width:620px){.course-grid.full{grid-template-columns:1fr}.explorer-controls{display:block}.numeric-form{display:block}.numeric-form button{margin-top:12px}.chapter-tabs{gap:7px}.chapter-tabs a{font-size:12px}.compare-box{grid-template-columns:1fr}.term-cards,.term-bins{gap:7px}}
.age-bar{height:15px;background:#76aa95;margin:15px 0}.route-track{position:relative;height:75px;border-bottom:5px solid #91aa9f;margin:20px 25px}.route-track span{position:absolute;bottom:4px;background:#d5e8da;padding:5px 10px;border-radius:8px;font-size:19px;transform:translateX(-50%)}.route-track span+span{transform:translateX(50%);background:#f0ddb8}.work-track{height:40px;background:white;border:1px solid #a8c5b5;border-radius:8px;display:flex;overflow:hidden;margin:25px 0}.work-track i{font-style:normal;background:#80b69a;display:grid;place-items:center;white-space:nowrap;font-size:19px}.work-track i+i{background:#e6b765}.chapter-grid{display:grid;grid-template-columns:1fr 1fr;gap:20px}@media(max-width:620px){.chapter-grid{grid-template-columns:1fr}}
.route-track span+span{bottom:37px}
