:root{color-scheme:light;--ink:#17191d;--muted:#666b75;--line:#e6e7eb;--bg:#f5f6f8;--card:#fff;--blue:#2269f2;--blue2:#0f4bd0;--sub:#f0f3f8;--radius:22px;--shadow:0 24px 85px rgba(27,35,64,.07);font-family:-apple-system,BlinkMacSystemFont,"SF Pro Display","PingFang SC","Microsoft YaHei",Arial,sans-serif}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--ink);font-size:16px;line-height:1.72}a{color:inherit;text-decoration:none}button,input,select{font:inherit}button,a{touch-action:manipulation}button{cursor:pointer}.nav{height:62px;position:sticky;top:0;z-index:20;border-bottom:1px solid rgba(255,255,255,.6);background:rgba(251,252,255,.8);backdrop-filter:blur(28px);-webkit-backdrop-filter:blur(28px)}.nav-in{max-width:1180px;margin:auto;height:100%;display:flex;align-items:center;justify-content:space-between;padding:0 22px}.brand{display:flex;gap:11px;align-items:center;font-weight:770;letter-spacing:-.045em;font-size:17px}.brandmark{width:27px;height:27px;background:#0a0a0b;color:white;border-radius:8px;display:grid;place-items:center;font-size:14px;font-weight:750}.links{display:flex;gap:24px;align-items:center;font-size:13px;color:#444b55}.links a:hover,.footer a:hover{color:var(--blue)}.navcta{border:1px solid #d6d9df;border-radius:60px;padding:7px 13px;background:white}.wrap{max-width:1180px;margin:auto;padding:0 22px}.hero{position:relative;overflow:hidden;padding:112px 0 87px;text-align:center;background:radial-gradient(ellipse 70% 54% at 50% 0%,rgba(176,205,255,.58),transparent),linear-gradient(160deg,#f9fafc 20%,#f3f6fd 65%,#f9fafc 100%)}.kicker{font-size:12px;letter-spacing:.15em;font-weight:800;color:#5e6581;text-transform:uppercase}.hero h1{font-size:clamp(46px,6.4vw,84px);letter-spacing:-.075em;line-height:1.13;font-weight:780;margin:21px auto 24px;max-width:970px}.grad{background:linear-gradient(115deg,#1449b6 2%,#588cfc 54%,#7436dc 95%);color:transparent;background-clip:text;-webkit-background-clip:text}.lead{max-width:735px;margin:auto;font-size:clamp(16px,2vw,20px);color:#545c67;line-height:1.9}.hero-actions{margin-top:32px;display:flex;justify-content:center;gap:13px;flex-wrap:wrap}.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;border-radius:40px;padding:12px 24px;background:var(--blue);color:white;border:1px solid var(--blue);font-weight:650;font-size:14px;transition:transform .2s,box-shadow .2s}.btn:hover{transform:translateY(-2px);box-shadow:0 8px 22px rgba(34,105,242,.2)}.btn.secondary{background:rgba(255,255,255,.8);color:#273042;border-color:#d9dee8}.stats{display:flex;justify-content:center;gap:48px;margin:52px auto 0;flex-wrap:wrap}.stat strong{display:block;font-weight:760;font-size:26px;letter-spacing:-.04em}.stat span{font-size:12px;color:var(--muted)}.section{padding:74px 0}.section-white{background:white}.heading{display:flex;justify-content:space-between;align-items:end;gap:24px;margin-bottom:27px}.heading h2{font-size:clamp(28px,3.8vw,43px);line-height:1.25;letter-spacing:-.055em;margin:7px 0;font-weight:760}.heading p{color:var(--muted);max-width:570px;margin:8px 0 0}.eyebrow{font-size:12px;color:var(--blue);font-weight:750;letter-spacing:.1em;text-transform:uppercase}.grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:18px}.tile{background:white;border:1px solid var(--line);border-radius:var(--radius);padding:27px;box-shadow:0 7px 30px rgba(20,34,66,.03);transition:transform .2s,border-color .2s}.tile:hover{transform:translateY(-4px);border-color:#c9d7f7}.tile .n{font-size:12px;color:#7f89a0;font-weight:740}.tile h3{font-size:19px;line-height:1.42;margin:20px 0 9px;letter-spacing:-.03em}.tile p{font-size:14px;color:#5c6270;margin:0}.tile .foot{border-top:1px solid #eef0f3;margin-top:21px;padding-top:17px;display:flex;justify-content:space-between;gap:12px;color:#566075;font-size:12px}.tag{font-size:12px;background:#edf3ff;color:#2354c5;border-radius:30px;padding:4px 11px;font-weight:650;display:inline-block}.searchbar{display:flex;align-items:center;gap:12px;margin:16px 0 24px}.searchbar input{background:white;border:1px solid #dfe2e8;border-radius:14px;padding:12px 16px;max-width:460px;width:100%;outline:none}.searchbar input:focus{border-color:#5689f9;box-shadow:0 0 0 4px #dce8ff}.filters{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:22px}.filter{background:#fff;border:1px solid #e2e5e9;padding:7px 13px;border-radius:99px;font-size:13px;color:#525c66}.filter.active{background:#16191e;color:white;border-color:#16191e}.progress-panel{margin:36px auto 0;background:#111722;color:white;border-radius:26px;padding:31px;display:flex;align-items:center;justify-content:space-between;gap:28px;text-align:left;max-width:830px}.progress-panel h3{margin:0 0 5px;font-size:20px}.progress-panel p{font-size:13px;color:#b9c4d5;margin:0}.bar{height:8px;border-radius:20px;background:#e4e7ed;overflow:hidden}.bar>div{height:100%;width:0;background:linear-gradient(90deg,#3881ff,#63c5fa);border-radius:20px;transition:width .3s}.progress-panel .bar{min-width:170px;background:#293448}.faint{color:var(--muted)}.reading{display:grid;grid-template-columns:230px minmax(0,1fr);gap:36px;padding-top:49px;padding-bottom:80px}.sidebar{position:sticky;top:90px;align-self:start;max-height:calc(100vh - 110px);overflow-y:auto;padding-right:6px}.side-title{font-size:12px;color:#8991a2;letter-spacing:.12em;font-weight:750;margin:0 0 12px}.side-link{display:block;border-radius:10px;padding:8px 10px;font-size:13px;color:#606979}.side-link:hover{background:#e8edf6}.side-link.current{background:#e5edfe;color:#215ac3;font-weight:700}.article{background:white;border:1px solid var(--line);padding:clamp(24px,5vw,62px);border-radius:28px;box-shadow:var(--shadow);min-width:0}.article h1{font-size:clamp(30px,4vw,52px);letter-spacing:-.055em;line-height:1.23;margin:16px 0 18px}.article .intro{font-size:18px;color:#535d6d;line-height:1.85}.article h2{font-size:26px;letter-spacing:-.04em;margin-top:42px}.article p,.article li{line-height:1.87}.article .example{background:#f4f7ff;border-left:3px solid #3375eb;padding:17px 20px;border-radius:0 12px 12px 0;color:#384a70;margin:23px 0}.step{border:1px solid #e8ebf1;border-radius:17px;padding:23px;margin:18px 0;background:#fff}.step-head{display:flex;align-items:flex-start;gap:14px}.step-num{width:32px;height:32px;flex:0 0 32px;border-radius:10px;background:#eef3ff;color:#2459c8;display:grid;place-items:center;font-weight:760;font-size:14px}.step h3{margin:0 0 8px;font-size:16px;line-height:1.55}.step-meta{font-size:13px;margin:12px 0 0;padding:13px 16px;background:#f6f7f9;border-radius:10px}.step-meta strong{color:#35415a}.checklabel{display:flex;align-items:center;gap:10px;color:#245cc0;font-size:13px;font-weight:680;margin:18px 0 0;cursor:pointer}.checklabel input,.daycheck{width:19px;height:19px;accent-color:#276df3}.ref-list{padding-left:20px;word-break:break-word}.ref-list li{padding:6px 0}.ref-list a{color:#1761cc;text-decoration:underline;text-decoration-color:#ccdafa;text-underline-offset:4px}.prevnext{display:flex;justify-content:space-between;gap:12px;margin-top:38px}.prevnext a{border:1px solid #e1e4e9;padding:11px 18px;border-radius:13px;font-size:14px;color:#2354bd}.minihero{padding:67px 0 36px}.minihero h1{font-size:clamp(33px,5vw,55px);letter-spacing:-.065em;line-height:1.23;margin:10px 0}.minihero p{font-size:16px;color:#647080;max-width:720px}.schedule{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px}.day{background:white;padding:22px;border:1px solid var(--line);border-radius:17px}.day.done{background:#f0f5ff;border-color:#afc7f7}.daytop{display:flex;align-items:center;justify-content:space-between;gap:15px}.day h3{margin:8px 0 10px;font-size:17px}.day p{font-size:14px;color:#555f6c;margin:0}.day .proof{margin-top:15px;padding-top:11px;border-top:1px solid #e7eaf0;font-size:12px;color:#65718a}.toolsgrid{display:grid;grid-template-columns:1fr 1fr;gap:20px}.toolcard{background:white;border:1px solid var(--line);border-radius:22px;padding:27px}.toolcard h2{font-size:21px;margin:0 0 8px}.toolcard p{font-size:14px;color:#596474}.fieldrow{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin:17px 0}.field label{font-size:12px;font-weight:700;display:block;color:#5a6575;margin-bottom:5px}.field input,.field select{padding:11px 12px;border-radius:11px;border:1px solid #d9dfe7;min-width:0;width:100%;background:#fff}.result{margin-top:20px;background:#f0f5ff;padding:20px;border-radius:14px;color:#25478c;font-size:15px}.result b{font-size:24px;color:#172a5b}.preview{margin-top:17px;border:1px solid #e2e4e8;border-radius:12px;padding:17px;background:#fff}.preview .url{font-size:12px;color:#39815e;overflow-wrap:anywhere}.preview .serptitle{font-size:18px;color:#1a0dab;margin:7px 0 3px}.preview .serpdesc{font-size:13px;color:#4b5563}.small{font-size:13px;color:#687385}.callout{background:#f0f4fb;border:1px solid #e0e9fa;padding:20px;border-radius:17px}.footer{padding:42px 22px 65px;background:#eceff4;color:#707782;font-size:13px}.footer-in{max-width:1180px;margin:auto;display:flex;justify-content:space-between;gap:25px;flex-wrap:wrap}.footer a{text-decoration:underline;text-underline-offset:3px}.hidden{display:none!important}.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0,0,0,0)}.focus:focus-visible,a:focus-visible,button:focus-visible,input:focus-visible{outline:3px solid #6ea4f9;outline-offset:3px}.notice{padding:13px 18px;border:1px solid #dde5f0;background:#f7faff;border-radius:12px;font-size:13px;color:#5b6575;margin-bottom:22px}.copyrow{display:flex;justify-content:space-between;align-items:center;gap:12px;padding:12px 0;border-bottom:1px solid #eaedf2}.copybtn{border:1px solid #d8dfeb;background:#fff;border-radius:9px;padding:5px 12px;font-size:12px;color:#1758d0}.breadcrumb{font-size:13px;color:#777f90}.breadcrumb a{color:#3d64ba}.trio{display:grid;grid-template-columns:repeat(3,1fr);gap:16px}.trio>div{padding:26px;background:white;border:1px solid var(--line);border-radius:22px}.trio b{display:block;font-size:16px}.trio p{font-size:14px;color:#647080}.progressline{height:3px;position:fixed;top:62px;left:0;width:0;background:var(--blue);z-index:25}.code{background:#111722;color:#dceafe;border-radius:13px;padding:20px;overflow:auto;font-size:13px;line-height:1.65;font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace}.toc{background:#f5f7fa;padding:21px;border-radius:15px}.toc a{color:#1f5ec2}.muted-list{font-size:14px;color:#626d79}
@media(max-width:850px){.grid{grid-template-columns:repeat(2,minmax(0,1fr))}.reading{grid-template-columns:1fr}.sidebar{display:none}.hero{padding:74px 0}.hero h1{font-size:clamp(43px,8vw,66px)}.progress-panel{max-width:100%}.toolsgrid{grid-template-columns:1fr}.links{gap:13px}.links .optional{display:none}}@media(max-width:600px){.grid,.schedule,.trio{grid-template-columns:1fr}.hero{padding:64px 0 60px}.hero h1{font-size:43px}.stats{gap:26px}.section{padding:46px 0}.nav-in{padding:0 16px}.brand{font-size:14px}.links{gap:9px;font-size:12px}.navcta{padding:6px 10px}.wrap{padding:0 16px}.heading{display:block}.progress-panel{flex-direction:column;align-items:stretch}.progress-panel .bar{min-width:0}.article{padding:24px;border-radius:20px}.reading{padding-top:20px}.fieldrow{grid-template-columns:1fr}.footer-in{display:block}}
@media(prefers-reduced-motion:reduce){*,*:before,*:after{animation:none!important;transition:none!important;scroll-behavior:auto!important}}

/* V2: route selector, no-JS read-through, mobile diagnostic and CSV lab */
.route-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:20px;align-items:start}.routecard{padding:30px;border:1px solid var(--line);border-radius:22px;background:white;scroll-margin-top:96px}.routecard h2{font-size:24px;letter-spacing:-.03em;line-height:1.35}.routecard>p,.routecard .milestones{color:#555c69;font-size:14px}.routecard a{color:var(--blue)}.routelist{margin:25px 0;padding:0;list-style:none;counter-reset:route}.routelist li{padding:14px 0 14px 31px;border-top:1px solid #e7ecf5;position:relative;counter-increment:route}.routelist li:before{content:counter(route);position:absolute;left:0;top:17px;background:#edf3ff;color:#2354c5;width:23px;height:23px;border-radius:50%;display:grid;place-items:center;font-weight:750;font-size:12px}.routelist li strong{font-size:14px;line-height:1.5;display:block}.routelist li p{color:var(--muted);margin:4px 0;font-size:13px}.routelist li a{font-size:12px}.milestones{background:#f7f9ff;border-radius:13px;padding:8px 16px}.selectlabel{display:block;margin:22px 0 9px;font-weight:650}.bigselect{width:100%;max-width:520px;background:#fff;border:1px solid #cbd8ee;border-radius:13px;padding:14px 18px;color:#1e293b}.formgrid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:22px;margin:20px 0}.formgrid .field select,.formgrid .field input{width:100%;border:1px solid #d7dfeb;border-radius:12px;padding:11px;background:white}.diagnostic{max-width:950px;margin:0 auto}.diagnostic .result{margin:22px 0}.diagnostic .result ol{padding-left:22px}.diagnostic .result a{color:var(--blue);font-weight:650}.table-wrap{overflow-x:auto;max-width:100%;margin:20px 0;border-radius:12px}.deci-table{border-collapse:collapse;width:100%;font-size:13px;background:#fff}.deci-table th,.deci-table td{border:1px solid #e4eaf2;padding:12px;text-align:left;vertical-align:top}.deci-table th{background:#eef4ff;font-weight:700;color:#364459}.deci-table td a{color:#1b59c7;text-decoration:underline}.deci-table td:first-child{overflow-wrap:anywhere;max-width:360px}.toolcard:has(#gscFile){max-width:950px;margin:0 auto}.toolcard select{color:#1c2432}#gscTable td{font-variant-numeric:tabular-nums}#gscStatus{margin:16px 0}@media(max-width:850px){.route-grid,.formgrid{grid-template-columns:1fr}}@media(max-width:600px){.routecard{padding:20px}.routecard h2{font-size:21px}.bigselect{font-size:14px}.deci-table th,.deci-table td{padding:9px;min-width:85px}}

/* Author conversion system: visible but not disruptive to learning. */
.nav-contact{background:#17191d!important;border-color:#17191d!important;color:#fff!important}
.nav-contact:hover{background:#343b49!important}
.author-strip{border-top:1px solid #dfe5ef;background:linear-gradient(112deg,#f5f8ff 8%,#fff 65%);padding:40px 0}
.author-strip-inner{display:grid;grid-template-columns:1.3fr 1fr;gap:30px;align-items:center}
.author-copy h2{font-size:clamp(21px,2.8vw,29px);line-height:1.35;letter-spacing:-.035em;margin:8px 0}
.author-copy p{font-size:14px;color:#647080;margin:0;max-width:600px}
.author-actions{display:flex;gap:10px;align-items:center;flex-wrap:wrap;justify-content:flex-end}
.author-actions .btn{padding:9px 16px;font-size:13px}
.wechat-line{display:flex;flex-basis:100%;gap:9px;justify-content:flex-end;align-items:center;flex-wrap:wrap;font-size:13px;color:#343f52}
.wechat-line strong,.contact-wechat{font-family:ui-monospace,SFMono-Regular,Menlo,monospace;letter-spacing:.015em}
.copy-wechat{padding:7px 13px;border:1px solid #bbceed;border-radius:9px;background:#fff;color:#174fa7;font-size:13px;font-weight:700;white-space:nowrap}
.copy-wechat:hover{background:#f0f6ff}
.copy-feedback{font-size:12px;color:#2a6546;min-height:1em}
.contact-secondary{font-size:12px;color:#185dca;text-decoration:underline;text-underline-offset:3px}
.home-author{padding:40px 0;background:#fff}
.home-author-card{display:grid;grid-template-columns:minmax(0,1fr) 260px;gap:38px;align-items:center;padding:clamp(25px,4vw,48px);background:linear-gradient(120deg,#f5f8ff,#fff);border:1px solid #dfe9fa;border-radius:28px}
.home-author-content h2{font-size:clamp(27px,3.5vw,43px);letter-spacing:-.055em;line-height:1.3;margin:12px 0}
.home-author-content p{max-width:720px;color:#5e6879;font-size:15px}
.home-author-content .hero-actions{justify-content:flex-start;margin-top:22px}
.home-author-note{background:#fff;border-radius:18px;border:1px solid #dfe5f1;display:flex;flex-direction:column;gap:10px;align-items:flex-start;padding:26px;box-shadow:0 14px 36px rgba(20,35,75,.04)}
.home-author-note>span:first-child{color:#778297;font-size:12px}
.home-author-note>strong{font-size:26px;letter-spacing:-.04em;font-family:ui-monospace,SFMono-Regular,Menlo,monospace}
.home-author-note>span:nth-of-type(2){font-size:13px;color:#626c7c}
.home-author-note>a{color:#175ab5;font-size:13px;text-decoration:underline}
.lesson-author-cta{border:1px solid #cddff6;border-radius:17px;background:linear-gradient(145deg,#f3f7ff,#fff);padding:23px;margin:30px 0 16px}
.lesson-author-cta h2{font-size:22px!important;margin:8px 0!important}
.lesson-author-cta p{font-size:14px;color:#566579;margin:5px 0 14px}
.lesson-author-actions{display:flex;gap:17px;flex-wrap:wrap}
.lesson-author-actions a{font-size:14px;color:#1456bd;text-decoration:underline;text-underline-offset:3px}
.contact-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:20px}
.contact-card{border-radius:24px;border:1px solid #e1e7f0;background:white;padding:clamp(24px,3vw,40px)}
.contact-card.primary{background:linear-gradient(150deg,#f1f6ff,#fff)}
.contact-card h2{font-size:clamp(23px,3vw,33px);overflow-wrap:anywhere;letter-spacing:-.04em;margin:15px 0}
.contact-card p{font-size:14px;color:#596579}
.contact-actions{display:flex;align-items:center;flex-wrap:wrap;gap:10px;margin-top:26px}
.contact-clarity{margin:28px 0}
.contact-back{display:flex;justify-content:space-between;gap:15px;flex-wrap:wrap}
.contact-back a{color:#1858ba;font-size:14px;text-decoration:underline}
@media(max-width:900px){.author-strip-inner{grid-template-columns:1fr}.author-actions,.wechat-line{justify-content:flex-start}.home-author-card{grid-template-columns:1fr}.home-author-note{max-width:390px}}
@media(max-width:650px){.links .nav-compact,.links .nav-github{display:none}.links{gap:8px}.nav-in{padding:0 15px;gap:8px}.brand{font-size:15px}.brandmark{width:24px;height:24px}.nav-contact{padding:7px 12px}.author-strip{padding:32px 0}.contact-grid{grid-template-columns:1fr}.home-author-card{padding:24px}.home-author-note{width:100%}.contact-card{padding:24px}}