:root{--bg:#f5f8f8;--paper:#fff;--ink:#102f36;--muted:#617a80;--line:#d7e5e7;--teal:#078997;--teal2:#11a7a8;--orange:#ee6b2f;--shadow:0 24px 70px rgba(18,55,61,.13);--font:16px}html[data-theme=dark]{--bg:#071113;--paper:#0d1b1f;--ink:#e8f4f4;--muted:#93aaae;--line:#20383d;--teal:#28b8c2;--teal2:#4ed0c8;--shadow:0 24px 70px rgba(0,0,0,.4)}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--ink);font:var(--font)/1.6 Inter,Segoe UI,Arial,sans-serif}.reading-bar{position:fixed;z-index:99;top:0;left:0;height:3px;background:linear-gradient(90deg,var(--orange),var(--teal));width:0}.topbar{height:72px;display:flex;align-items:center;justify-content:space-between;padding:0 4vw;background:color-mix(in srgb,var(--paper) 92%,transparent);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:20;backdrop-filter:blur(16px)}.brand{display:flex;align-items:center;gap:12px;text-decoration:none;color:var(--ink);letter-spacing:.08em}.brand-mark{width:42px;height:42px;display:grid;place-items:center;border-radius:13px;background:linear-gradient(135deg,var(--orange),var(--teal));color:#fff;font-size:27px}.brand span:last-child{display:flex;flex-direction:column}.brand small{font-size:.72rem;letter-spacing:0;color:var(--muted)}.controls{display:flex;gap:9px;align-items:center}.controls button,.runtime-link{border:1px solid var(--line);background:var(--paper);color:var(--ink);border-radius:11px;padding:9px 13px;text-decoration:none;font:inherit;cursor:pointer}.runtime-link{background:var(--ink);color:var(--paper);border-color:var(--ink)}main{max-width:1500px;margin:auto}.hero{min-height:690px;padding:90px 5vw 70px;display:grid;grid-template-columns:minmax(0,1.1fr) minmax(430px,.9fr);align-items:center;gap:70px}.eyebrow{font-size:.78rem;font-weight:800;letter-spacing:.2em;color:var(--teal);margin:0 0 14px}.hero h1{font-size:clamp(3.4rem,6.3vw,6.8rem);line-height:.92;letter-spacing:-.065em;margin:0;max-width:850px}.lead{font-size:1.18rem;max-width:750px;color:var(--muted);margin:30px 0}.hero-actions{display:flex;gap:12px;flex-wrap:wrap}.primary,.secondary{display:inline-flex;align-items:center;justify-content:center;padding:13px 18px;border-radius:12px;text-decoration:none;font-weight:750}.primary{background:var(--teal);color:#fff}.secondary{border:1px solid var(--line);color:var(--ink);background:var(--paper)}.feature-row{display:flex;flex-wrap:wrap;gap:8px;margin-top:25px}.feature-row span{border:1px solid var(--line);background:var(--paper);padding:6px 10px;border-radius:999px;color:var(--muted);font-size:.8rem}.hero-stage{min-height:510px;border-radius:34px;background:radial-gradient(circle at 75% 10%,rgba(36,207,205,.24),transparent 42%),linear-gradient(150deg,color-mix(in srgb,var(--paper) 92%,#e9ffff),color-mix(in srgb,var(--paper) 86%,#e9f2f3));box-shadow:var(--shadow);position:relative;overflow:hidden;border:1px solid var(--line)}.hero-stage svg{position:absolute;left:7%;right:7%;width:86%;bottom:5%;height:42%}.grid{fill:none;stroke:var(--line);stroke-width:1}.line{fill:none;stroke:var(--teal2);stroke-width:6;stroke-linecap:round}.area{fill:color-mix(in srgb,var(--teal2) 20%,transparent)}.window-card{position:absolute;left:7%;top:9%;width:74%;border-radius:15px;overflow:hidden;background:#0e1c20;color:#d9f3f1;box-shadow:0 18px 50px rgba(0,0,0,.22);transform:rotate(-2deg)}.window-head{height:42px;background:#163139;display:flex;align-items:center;padding:0 14px;gap:7px}.window-head i{width:10px;height:10px;border-radius:50%;background:#ef6b4e}.window-head i:nth-child(2){background:#f0bd52}.window-head i:nth-child(3){background:#48c487}.window-head b{margin-left:8px;font-size:.8rem}.window-card pre{margin:0;padding:22px;font:600 .95rem/1.9 ui-monospace,Consolas,monospace}.window-card pre span{color:#65e1dc}.matrix-float{position:absolute;right:6%;top:44%;background:var(--paper);padding:18px;border:1px solid var(--line);border-radius:15px;box-shadow:var(--shadow);transform:rotate(4deg)}.matrix-float b{display:block;color:var(--orange);margin-bottom:5px}.matrix-float div{font:700 1rem/1.5 ui-monospace,monospace;word-spacing:10px}.overview{padding:90px 5vw}.section-title{display:flex;justify-content:space-between;gap:30px;align-items:end;margin-bottom:34px}.section-title h2,.runtime-section h2{font-size:clamp(2.1rem,4vw,4rem);line-height:1;letter-spacing:-.045em;margin:0}.section-title>p{max-width:560px;color:var(--muted)}.lesson-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:16px}.lesson-card{min-height:315px;position:relative;display:flex;flex-direction:column;border:1px solid var(--line);border-radius:22px;padding:24px;background:var(--paper);color:var(--ink);text-decoration:none;transition:.25s ease;overflow:hidden}.lesson-card:hover{transform:translateY(-5px);box-shadow:var(--shadow);border-color:color-mix(in srgb,var(--teal) 45%,var(--line))}.lesson-card.live:before{content:"";position:absolute;inset:0 0 auto;height:5px;background:linear-gradient(90deg,var(--orange),var(--teal))}.lesson-no{font-weight:900;color:var(--muted);font-size:.8rem}.status{position:absolute;right:20px;top:19px;padding:4px 8px;border-radius:999px;background:color-mix(in srgb,var(--teal) 12%,transparent);color:var(--teal);font-size:.64rem;font-weight:900;letter-spacing:.12em}.status.new{background:color-mix(in srgb,var(--orange) 13%,transparent);color:var(--orange)}.lesson-card h3{font-size:1.4rem;line-height:1.15;margin:36px 0 10px}.lesson-card p{color:var(--muted);margin:0}.topics{display:flex;gap:6px;flex-wrap:wrap;margin-top:auto;padding-top:20px}.topics i{font-style:normal;font-size:.68rem;border:1px solid var(--line);padding:4px 7px;border-radius:7px}.open{margin-top:16px;color:var(--teal)}.planned{opacity:.78}.runtime-section{margin:40px 5vw 100px;padding:60px;border:1px solid var(--line);border-radius:30px;background:linear-gradient(135deg,var(--paper),color-mix(in srgb,var(--paper) 88%,#ccffff));display:grid;grid-template-columns:1fr 1fr;gap:60px}.runtime-copy p{color:var(--muted)}.runtime-copy ul{padding-left:20px;margin-bottom:30px}.architecture{display:flex;flex-direction:column;gap:10px;justify-content:center}.architecture div{display:grid;grid-template-columns:180px 1fr;gap:16px;padding:14px 16px;border:1px solid var(--line);border-radius:12px;background:color-mix(in srgb,var(--paper) 88%,transparent)}.architecture b{font-family:ui-monospace,monospace;color:var(--teal)}.architecture span{color:var(--muted)}footer{border-top:1px solid var(--line);padding:24px 5vw;display:flex;justify-content:space-between;color:var(--muted)}footer a{color:var(--teal)}.tooltip{position:fixed;z-index:1000;display:none;max-width:360px;background:#0e2428;color:#f0ffff;border:1px solid #315057;border-radius:10px;padding:9px 12px;font-size:.82rem;box-shadow:0 12px 30px rgba(0,0,0,.24);pointer-events:none}@media(max-width:1100px){.hero{grid-template-columns:1fr}.hero-stage{min-height:430px}.lesson-grid{grid-template-columns:repeat(2,1fr)}.runtime-section{grid-template-columns:1fr}}@media(max-width:680px){.topbar{padding:0 16px}.brand b{font-size:.75rem}.brand small{display:none}.runtime-link span:last-child{display:none}.hero{padding:60px 20px}.hero h1{font-size:3.5rem}.lesson-grid{grid-template-columns:1fr}.overview{padding:60px 20px}.section-title{display:block}.runtime-section{margin:20px;padding:28px}.architecture div{grid-template-columns:1fr}.controls{gap:5px}.controls button,.runtime-link{padding:8px}.hero-stage{min-height:350px}}.font-box{display:inline-flex;align-items:center;height:40px}.font-box button{height:100%;border:0;background:transparent;padding:0 9px;cursor:pointer}.font-box span{min-width:29px;text-align:center;font-weight:750;color:var(--muted)}
@media(max-width:940px){#tipToggle,.controls .font-box{display:none}}


/* v1.2.1 student-facing home and performance */
.topbar{backdrop-filter:none!important;-webkit-backdrop-filter:none!important;background:var(--paper)!important}
.overview,.runtime-section{content-visibility:auto;contain-intrinsic-size:auto 850px}
.learning-path{display:flex;align-items:center;justify-content:center;gap:12px;flex-wrap:wrap}
.learning-path div{width:150px;min-height:118px;border:1px solid var(--line);border-radius:18px;background:var(--paper);display:flex;flex-direction:column;align-items:center;justify-content:center;text-align:center;padding:16px;box-shadow:0 10px 28px rgba(18,55,61,.06)}
.learning-path b{width:36px;height:36px;display:grid;place-items:center;border-radius:50%;background:var(--teal);color:#fff;margin-bottom:10px}.learning-path i{font-style:normal;color:var(--teal);font-size:1.6rem}
@media(max-width:680px){.learning-path i{transform:rotate(90deg)}}

/* v1.2.2 refined home entrance */
.hero-stage{opacity:0;transform:translateY(20px) scale(.985);animation:heroStageReveal .72s cubic-bezier(.2,.78,.25,1) .08s forwards}
.hero-stage .window-card{opacity:0;animation:heroWindowReveal .62s cubic-bezier(.2,.8,.25,1) .32s forwards}
.hero-stage .matrix-float{opacity:0;animation:heroMatrixReveal .58s cubic-bezier(.2,.8,.25,1) .52s forwards}
.hero-stage svg .line{stroke-dasharray:620;stroke-dashoffset:620;animation:heroLineDraw 1.25s ease .68s forwards}
.hero-stage svg .area{opacity:0;animation:heroAreaReveal .6s ease 1.05s forwards}
@keyframes heroStageReveal{to{opacity:1;transform:none}}
@keyframes heroWindowReveal{from{opacity:0;transform:translateY(-14px) rotate(-4deg)}to{opacity:1;transform:rotate(-2deg)}}
@keyframes heroMatrixReveal{from{opacity:0;transform:translate(18px,14px) rotate(7deg)}to{opacity:1;transform:rotate(4deg)}}
@keyframes heroLineDraw{to{stroke-dashoffset:0}}
@keyframes heroAreaReveal{to{opacity:1}}
@media(prefers-reduced-motion:reduce){.hero-stage,.hero-stage .window-card,.hero-stage .matrix-float,.hero-stage svg .line,.hero-stage svg .area{animation:none!important;opacity:1!important;transform:none!important;stroke-dashoffset:0!important}}
.lesson-card.l5::before{background:linear-gradient(90deg,#7467d7,#27b7c6)}


/* v1.3.1: visual-rhythm pass for compact classroom screens. */
html[lang="zh-CN"] .hero h1{
  font-size:clamp(3rem,5.35vw,5.8rem);
  line-height:1.11;
  letter-spacing:-.045em;
}
html[lang="zh-CN"] .hero .lead{line-height:1.78}
html[lang="zh-CN"] .section-title h2,
html[lang="zh-CN"] .runtime-section h2{
  line-height:1.2;
  letter-spacing:-.035em;
}
.overview .section-title h2{font-size:clamp(2rem,3vw,3.15rem)}
.lesson-card h3{line-height:1.3;letter-spacing:-.018em}
.lesson-card p{line-height:1.68}
.runtime-copy p,.runtime-copy li{line-height:1.72}
@media(min-width:1101px){
  .overview .section-title>div{min-width:0;flex:1 1 auto}
  .overview .section-title h2{white-space:nowrap}
  .overview .section-title>p{flex:0 1 470px;margin-bottom:.35rem}
}
@media(max-width:1450px) and (min-width:1101px){
  .hero{gap:48px;padding-left:5vw;padding-right:5vw}
  .hero-stage{min-height:470px}
  .overview{padding-top:76px;padding-bottom:76px}
  .lesson-card{padding:22px;min-height:305px}
  .lesson-card h3{font-size:1.3rem}
  .runtime-section{gap:42px;padding:48px}
}
@media(max-width:1100px){
  html[lang="zh-CN"] .hero h1{font-size:clamp(3rem,8vw,5rem)}
  .section-title{align-items:start}
}
@media(max-width:680px){
  html[lang="zh-CN"] .hero h1{font-size:clamp(2.75rem,13vw,3.65rem);line-height:1.13}
  .overview .section-title h2{font-size:2.15rem;line-height:1.24}
  .lesson-card h3{font-size:1.3rem}
}

.lesson-card.l6::before{background:linear-gradient(90deg,#ec7b36,#0aa3ad)}

/* Lesson 07 course-card accent */
.lesson-card.l7::before{background:linear-gradient(90deg,#f0a13c,#17a9b3)}


/* v1.8.13: one visual family for the second row of course cards. */
.lesson-card.l5::before,.lesson-card.l6::before,.lesson-card.l7::before,.lesson-card.l8::before{
  background:linear-gradient(90deg,#6277ef 0%,#3d91e8 45%,#25c5d2 100%);
}