:root{color-scheme:light;--ink:#202124;--muted:#696b71;--line:#e5e5e7;--blue:#0869d1;--paper:#fafafa;--font:-apple-system,BlinkMacSystemFont,"SF Pro Display","PingFang SC","Microsoft YaHei",sans-serif}
*{box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:90px}
body{margin:0;background:var(--paper);color:var(--ink);font-family:var(--font);font-size:16px;-webkit-font-smoothing:antialiased}
a{color:inherit;text-decoration:none}button{font:inherit;cursor:pointer}button,a,summary{-webkit-tap-highlight-color:transparent}button{border:0}img{max-width:100%;display:block}[hidden]{display:none!important}
button:focus-visible,a:focus-visible,summary:focus-visible{outline:3px solid var(--blue);outline-offset:6px}
.wrap{width:min(1120px,calc(100% - 96px));margin-inline:auto}.section{padding-block:100px}.eyebrow{margin:0 0 24px;font-size:12px;font-weight:600;letter-spacing:2.2px;color:var(--muted)}
.header{background:#fafafae8;border-bottom:1px solid var(--line);position:sticky;top:0;z-index:10;backdrop-filter:blur(18px)}.nav{height:76px;display:flex;align-items:center;justify-content:space-between;gap:24px}.brand{display:flex;align-items:center;gap:14px;font-size:16px;font-weight:600;letter-spacing:-.3px}.brand img{object-fit:contain}.brand-divider{color:#b7b7bb;margin:0 8px;font-weight:400}.brand-cn{font-size:14px;font-weight:400}.nav-links{display:flex;align-items:center;gap:32px;font-size:14px}.nav-links a:hover{color:var(--blue)}.nav-community{border-left:1px solid #d7d7da;padding-left:30px}.nav-community span{margin-left:7px}
.hero{display:grid;grid-template-columns:1.2fr 1fr;align-items:center;min-height:624px;gap:40px;padding-block:68px}.hero .eyebrow{font-size:12px;letter-spacing:2.4px;margin-bottom:30px}h1{font-size:clamp(48px,5.4vw,72px);line-height:1.2;letter-spacing:-3px;font-weight:600;margin:0 0 27px}.blue{color:var(--blue)}.hero-description{font-size:19px;line-height:1.85;color:var(--muted);margin:0}.hero-actions{margin-top:34px;display:flex;align-items:center;gap:16px;flex-wrap:wrap}.button{display:inline-flex;align-items:center;justify-content:center;gap:24px;border-radius:999px;padding:15px 25px;font-size:15px;font-weight:500;transition:background .2s,transform .2s}.button:hover{transform:translateY(-2px)}.primary{background:var(--blue);color:#fff}.primary:hover{background:#0759b1}.shop-shortcut{background:#eaf3fd;color:var(--blue);gap:10px}.shop-shortcut:hover{background:#d9eaff}.text-link{font-size:15px;color:var(--blue)}.text-link span{margin-left:6px}.hero-art{margin:0;text-align:center;align-self:center}.cube-stage{padding:24px 22px 46px;position:relative}.hero-cube{width:340px;height:350px;margin:auto;position:relative;z-index:1;animation:arrive 1s ease-out both}.cube-stage:after{content:"";position:absolute;bottom:8px;left:25%;width:50%;height:22px;background:#23232622;filter:blur(19px);border-radius:50%}.hero-art figcaption{display:flex;justify-content:center;align-items:center;gap:12px;font-size:12px;color:#75757b;margin-top:18px;letter-spacing:1px}.tiny-colors{display:inline-flex;gap:4px}.tiny-colors i{width:6px;height:6px;border-radius:1px;background:#006dd2}.tiny-colors i:nth-child(2){background:#e9272e}.tiny-colors i:nth-child(3){background:#e6c300}
.intro-strip{padding-block:26px;display:flex;align-items:center;gap:18px;border-top:1px solid var(--line);border-bottom:1px solid var(--line);font-size:14px}.intro-strip>span:first-child{font-weight:600}.intro-strip p{margin:0;color:var(--muted)}.math-note{margin-left:auto;font:18px Georgia,serif;color:#77777e;letter-spacing:2px}
h2{font-size:38px;letter-spacing:-1.3px;line-height:1.35;font-weight:600;margin:0}.section-heading{display:flex;justify-content:space-between;align-items:flex-end;gap:30px;margin-bottom:38px}.section-heading .eyebrow{margin-bottom:15px}.section-heading>p{color:var(--muted);line-height:1.9;font-size:15px;margin:0 0 3px}.lesson-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px;align-items:start}.lesson{background:#fff;border:1px solid #e9e9ec;border-radius:16px;overflow:hidden;transition:border-color .2s}.lesson:hover,.lesson[open]{border-color:#b7cbe2}.lesson summary{list-style:none;cursor:pointer;padding:27px 26px 24px}.lesson summary::-webkit-details-marker{display:none}.lesson-top{display:flex;align-items:center;justify-content:space-between;font-size:12px;color:var(--muted);letter-spacing:.5px}.lesson-expand{font-size:21px;font-weight:300;line-height:1;transition:transform .2s}.lesson[open] .lesson-expand{transform:rotate(45deg)}.lesson-visual{display:flex;align-items:center;justify-content:center;height:146px;font-family:Georgia,"Times New Roman",serif;font-size:64px;letter-spacing:-3px}.count-visual{color:#b29414}.count-visual>span{font-size:30px;letter-spacing:-1px;margin:14px 0 0 8px}.count-visual sup{font-size:16px;position:relative;top:-5px}.group-visual{color:#1167b9;font-style:italic}.subgroup-visual{color:#c23b41;font-style:italic}.subgroup-visual>span{font-size:38px;margin:0 18px;font-style:normal}.lesson-title{display:block;font-size:19px;font-weight:600;letter-spacing:-.5px;line-height:1.5}.lesson-description{display:block;color:var(--muted);font-size:14px;line-height:1.8;margin-top:11px;min-height:52px}.lesson-bottom{margin-top:27px;display:flex;justify-content:space-between;padding-top:18px;border-top:1px solid #ededf0;font-size:12px;color:#77777d}.lesson-detail{padding:0 26px 25px;font-size:14px;line-height:1.8}.lesson-detail p{margin:0 0 18px}.platform-link{color:var(--blue)}.upcoming{display:flex;align-items:center;gap:26px;margin-top:30px;font-size:13px}.upcoming-label{color:var(--muted)}.upcoming p{margin:0;line-height:1.9}.upcoming p span{color:#c2c2c7;margin:0 16px}.coming-tag{margin-left:auto;border:1px solid var(--line);padding:6px 10px;border-radius:5px;white-space:nowrap;color:var(--muted);font-size:12px}
.creator{background:#f0f1f3}.creator-layout{display:grid;grid-template-columns:1.1fr 1fr;gap:90px;align-items:center}.creator .eyebrow{margin-bottom:20px}.creator-handle{font-size:19px;color:#595b62;margin:15px 0 24px}.creator-description{font-size:16px;color:var(--muted);line-height:1.95}.signature{display:block;font-family:"Songti SC",Georgia,serif;font-size:29px;margin-top:28px}.signature>span{font:12px var(--font);margin-left:15px;color:#77777e;letter-spacing:1px}.social-list{display:flex;flex-direction:column;gap:16px}.social-card{padding:25px;background:#fff;border-radius:14px;display:flex;align-items:center;gap:20px;transition:transform .2s}.social-card:hover{transform:translateY(-3px)}.social-card img{border-radius:10px;object-fit:contain}.social-card>span:nth-child(2){display:flex;flex-direction:column;gap:9px;flex:1}.social-card strong{font-weight:600;font-size:18px}.social-card span span{color:var(--muted);font-size:14px;line-height:1.6}.social-card small{color:var(--blue);font-size:12px}.social-arrow{color:#787880;font-size:22px}
.product-card{cursor:default;scroll-margin-top:110px}.product-card:hover{transform:none}.product-card:target{outline:2px solid #9bc9f5;animation:shop-focus 2.5s ease-out}.product-card>img{border-radius:0;flex:none}.product-card-copy{display:flex;flex-direction:column;gap:9px;min-width:0}.product-card-copy>span{color:var(--muted);font-size:14px;line-height:1.6}.product-card-copy>.shop-kicker{align-self:flex-start;padding:5px 9px;border-radius:6px;background:#eaf3fd;color:var(--blue);font-size:11px;font-weight:600;line-height:1.2}.product-card-copy>small{color:var(--blue);font-size:13px;font-weight:600}.shop-links{display:flex;gap:16px;flex-wrap:wrap}.shop-links a{color:var(--blue);font-size:13px}.shop-links a:hover{text-decoration:underline}
.community{padding-block:80px}.community-panel{background:#202226;color:#f9f9fb;border-radius:22px;padding:64px 70px;display:grid;grid-template-columns:1.2fr 1fr;gap:40px;align-items:center}.community .eyebrow{color:#a6a8ae;margin-bottom:22px}.community h2{font-size:42px;line-height:1.35}.community p:not(.eyebrow){color:#b7b8bf;font-size:16px;line-height:1.9;margin:22px 0 28px}.light{background:#fff;color:#202226}.light:hover{background:#e4e9f0}.community-formula{text-align:center}.community-formula>span{font-family:Georgia,serif;font-size:86px;font-weight:400;letter-spacing:6px}.community-formula>div{height:1px;background:#55565b;width:88px;margin:28px auto}.community-formula small{font-size:12px;color:#a6a8ae;letter-spacing:2px}
.footer{border-top:1px solid var(--line);padding-block:29px;display:flex;align-items:center;justify-content:space-between;gap:24px;font-size:12px;color:var(--muted)}.footer .brand{font-size:14px;color:var(--ink)}.footer p{margin:0}
dialog{border:1px solid var(--line);border-radius:22px;width:min(440px,calc(100% - 32px));padding:42px 36px;text-align:center;max-height:calc(100dvh - 40px);color:var(--ink);background:#fff}dialog::backdrop{background:#171b256b;backdrop-filter:blur(6px)}dialog .eyebrow{margin-bottom:16px}dialog h2{font-size:29px}dialog>p:not(.eyebrow){font-size:14px;line-height:1.8;color:var(--muted)}.dialog-close{position:absolute;right:16px;top:12px;background:transparent;font-size:28px;color:#6e7076;width:36px;height:36px;border-radius:50%}.qr-area{background:#f5f6f8;border-radius:14px;padding:28px 18px;margin:22px 0;display:flex;align-items:center;flex-direction:column;gap:12px}.wechat-symbol{border:1px solid #c9cdd3;border-radius:16px;width:54px;height:54px;display:grid;place-items:center;font-size:24px;color:#696b71}.qr-area strong{font-size:16px;font-weight:500}.qr-area p{font-size:14px;line-height:1.8;margin:0;color:var(--muted)}.dialog-note{font-size:12px!important;margin-bottom:0}.wechat-qr{width:230px;height:auto;object-fit:contain;padding:16px;background:#fff;box-sizing:content-box;max-width:calc(100% - 32px)}#copy-wechat{max-width:100%;overflow-wrap:anywhere}.toast{position:fixed;z-index:30;bottom:26px;left:50%;transform:translate(-50%,12px);background:#24262a;color:#fff;box-shadow:0 4px 30px #0002;border-radius:10px;padding:13px 20px;font-size:14px;opacity:0;pointer-events:none;transition:opacity .2s,transform .2s;max-width:calc(100% - 40px);text-align:center;overflow-wrap:anywhere}.toast.visible{opacity:1;transform:translate(-50%,0)}.skip-link{position:fixed;top:-80px;left:16px;z-index:50;background:#fff;padding:15px}.skip-link:focus{top:15px}
@keyframes arrive{from{opacity:0;transform:translateY(14px)}to{opacity:1;transform:translateY(0)}}
@keyframes shop-focus{0%{box-shadow:0 0 0 0 #0869d166}35%{box-shadow:0 0 0 12px #0869d122}100%{box-shadow:0 0 0 0 #0869d100}}
@media(min-width:1500px){.hero{min-height:670px}.hero-cube{width:370px;height:380px}}
@media(max-width:1000px){.wrap{width:calc(100% - 64px)}.hero{gap:20px;min-height:570px}.hero-cube{width:280px;height:290px}.hero-description{font-size:17px}.brand-cn,.brand-divider{display:none}.lesson summary{padding:24px 20px}.lesson-title{font-size:17px}.lesson-detail{padding-inline:20px}.creator-layout{gap:40px}.community-panel{padding:55px 48px}.upcoming{gap:16px}.upcoming p span{margin:0 8px}.social-card{padding:22px 18px;gap:14px}}
@media(max-width:740px){html{scroll-padding-top:80px}.wrap{width:calc(100% - 40px)}.nav{height:66px;gap:10px}.brand{font-size:14px;gap:9px}.brand img{width:32px;height:32px}.nav-links{gap:19px;font-size:13px}.nav-community{padding-left:0;border:0}.nav-community span{display:none}.nav-links>a:nth-child(2){display:none}.hero{grid-template-columns:1fr;gap:22px;padding-top:54px;padding-bottom:32px;min-height:auto;text-align:center}.hero .eyebrow{font-size:10px;letter-spacing:1.8px;margin-bottom:22px}h1{font-size:49px;letter-spacing:-2px;margin-bottom:21px}.hero-description{font-size:16px;line-height:1.85}.hero-actions{justify-content:center;gap:14px;margin-top:25px}.hero-actions .shop-shortcut{flex-basis:100%}.button{font-size:14px;padding:14px 23px;gap:18px}.text-link{font-size:14px}.hero-cube{width:235px;height:240px}.cube-stage{padding:12px 0 29px}.cube-stage:after{left:33%;width:34%;height:16px;filter:blur(15px)}.hero-art figcaption{margin-top:12px;font-size:12px}.intro-strip{padding-block:23px;gap:10px;justify-content:center;font-size:12px;flex-wrap:wrap}.math-note{display:none}.section{padding-block:62px}h2{font-size:31px;letter-spacing:-1px}.section-heading{display:block;margin-bottom:26px}.section-heading>p{margin-top:19px;font-size:14px}.eyebrow{font-size:11px;letter-spacing:1.8px}.lesson-grid{grid-template-columns:1fr;gap:14px}.lesson summary{padding:25px}.lesson-visual{height:118px;font-size:58px}.lesson-title{font-size:20px}.lesson-description{min-height:0;font-size:15px}.lesson-bottom{margin-top:22px}.lesson-detail{padding-inline:25px}.upcoming{flex-wrap:wrap;gap:10px;font-size:12px}.upcoming-label{flex-basis:100%;font-size:13px}.upcoming p{font-size:13px}.coming-tag{margin-left:0}.creator-layout{grid-template-columns:1fr;gap:32px}.creator-description{font-size:15px}.creator-handle{font-size:17px}.social-card{padding:22px}.community-panel{padding:39px 27px;grid-template-columns:1fr;gap:30px;border-radius:18px}.community h2{font-size:35px}.community p:not(.eyebrow){font-size:15px}.community-formula{padding-top:24px;border-top:1px solid #45474b}.community-formula>span{font-size:58px}.community-formula>div{margin:18px auto}.footer{flex-wrap:wrap;justify-content:space-between;padding-block:26px;row-gap:20px}.footer p{order:3;flex-basis:100%;text-align:center;font-size:12px}.footer>span{font-size:11px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*:before,*:after{animation:none!important;transition:none!important}}