@import url('https://fonts.googleapis.com/css2?family=Noto+Serif+SC:wght@500;700;900&family=Noto+Sans+SC:wght@400;500;700&family=JetBrains+Mono:wght@400;600&display=swap');

:root{
  --ink:#14171f; --ink-soft:#1d2230; --ink-card:#242a3a; --ink-card-hi:#2c3346;
  --brass:#c9952c; --brass-soft:#a87818; --brass-dim:#8a6620;
  --rust:#c1543a; --rust-soft:#a8452f;
  --teal:#2f8a76; --teal-soft:#226b5a;
  --paper:#f6f1e4; --paper-card:#fffdf6; --paper-soft:#efe8d4;
  --text-light:#ece7da; --text-dim:#9aa0b4; --text-faint:#6b7080;
  --text-dark:#20242c; --text-dark-dim:#5b5a4f; --text-dark-faint:#8a8472;
  --line:rgba(60,40,10,0.10);
  --line-strong:rgba(60,40,10,0.18);
  --shadow:0 8px 24px rgba(60,40,10,.10);
  --shadow-hover:0 14px 32px rgba(60,40,10,.16);
}
*{box-sizing:border-box;margin:0;padding:0;}
html{scroll-behavior:smooth;}
body{
  background:var(--paper);color:var(--text-dark);
  font-family:'Noto Sans SC',sans-serif;line-height:1.7;
  -webkit-font-smoothing:antialiased;
}
code,.mono{font-family:'JetBrains Mono','Noto Sans SC',monospace;}
h1,h2,h3,.serif{font-family:'Noto Serif SC',serif;}
a{color:inherit;text-decoration:none;}

/* ============ 顶部导航 ============ */
.topbar{
  position:fixed;top:0;left:0;right:0;height:54px;z-index:50;
  display:flex;align-items:center;justify-content:space-between;
  padding:0 22px;
  background:rgba(246,241,228,0.92);backdrop-filter:blur(6px);
  border-bottom:1px solid var(--line);font-size:13px;
}
.topbar .brand{display:flex;align-items:center;gap:10px;}
.topbar .brand .logo{font-size:20px;}
.topbar .brand .name{
  color:var(--text-dark);font-weight:700;font-size:15px;
  font-family:'Noto Serif SC',serif;
}
.topbar .brand .name b{color:var(--brass);}
.topbar nav{display:flex;gap:24px;}
.topbar nav a{
  color:var(--text-dark-dim);cursor:pointer;font-size:13px;
  transition:color .2s ease;position:relative;
}
.topbar nav a:hover{color:var(--brass);}
.topbar nav a.active{color:var(--brass);}
.topbar nav a.active::after{
  content:'';position:absolute;left:0;right:0;bottom:-6px;
  height:2px;background:var(--brass);border-radius:2px;
}
.topbar .tools{display:flex;gap:14px;align-items:center;color:var(--text-dark-dim);font-size:12px;}
.topbar .tools .pill{
  padding:3px 10px;border-radius:20px;
  background:rgba(201,149,44,0.15);color:var(--brass);font-size:11px;
}

/* ============ Hero ============ */
.hero{
  min-height:100vh;display:flex;flex-direction:column;
  align-items:center;justify-content:center;
  text-align:center;padding:120px 8vw 80px;position:relative;overflow:hidden;
  background:radial-gradient(ellipse at 30% 20%,#fffbef 0%,var(--paper) 65%);
}
.hero::before{
  content:'';position:absolute;inset:0;
  background-image:
    radial-gradient(circle at 80% 15%,rgba(201,149,44,0.12),transparent 40%),
    radial-gradient(circle at 15% 80%,rgba(193,84,58,0.08),transparent 45%);
  pointer-events:none;
}
.hero .emblem{
  width:110px;height:110px;margin-bottom:26px;
  display:flex;align-items:center;justify-content:center;font-size:72px;
  filter:drop-shadow(0 8px 24px rgba(201,149,44,0.35));
  animation:float 6s ease-in-out infinite;
}
@keyframes float{0%,100%{transform:translateY(0);}50%{transform:translateY(-10px);}}
.hero .eyebrow{
  font-size:12px;letter-spacing:.22em;color:var(--brass);
  font-weight:700;margin-bottom:18px;text-transform:uppercase;
}
.hero h1{
  font-size:clamp(34px,5.5vw,68px);line-height:1.2;font-weight:900;
  max-width:900px;margin-bottom:22px;color:var(--text-dark);
}
.hero h1 .accent{color:var(--brass);}
.hero h1 .strike{
  position:relative;display:inline-block;
}
.hero h1 .strike::after{
  content:'';position:absolute;left:-4%;right:-4%;top:55%;height:6px;
  background:var(--rust);border-radius:3px;transform:rotate(-2deg);
}
.hero .sub{
  font-size:clamp(15px,1.6vw,19px);color:var(--text-dark-dim);
  max-width:620px;margin-bottom:40px;line-height:1.8;
}
.hero .cta{display:flex;gap:16px;flex-wrap:wrap;justify-content:center;}
.hero .btn{
  padding:13px 30px;border-radius:30px;font-size:14px;font-weight:700;
  cursor:pointer;border:none;transition:all .2s ease;
  font-family:'Noto Sans SC',sans-serif;
}
.hero .btn-primary{
  background:var(--brass);color:#fffdf6;
  box-shadow:0 8px 22px rgba(201,149,44,0.30);
}
.hero .btn-primary:hover{transform:translateY(-2px);box-shadow:0 12px 28px rgba(201,149,44,0.40);}
.hero .btn-ghost{
  background:transparent;color:var(--text-dark);
  border:1px solid var(--line-strong);
}
.hero .btn-ghost:hover{border-color:var(--brass);color:var(--brass);}
.hero .stats{
  display:flex;gap:50px;margin-top:64px;flex-wrap:wrap;justify-content:center;
}
.hero .stats .st{text-align:center;}
.hero .stats .st .num{
  font-family:'Noto Serif SC',serif;font-size:34px;font-weight:700;
  color:var(--brass);
}
.hero .stats .st .lab{font-size:12px;color:var(--text-dark-dim);margin-top:4px;}

/* ============ 学习路径条 ============ */
.pathbar{
  background:var(--paper-soft);border-top:1px solid var(--line);
  border-bottom:1px solid var(--line);
  padding:26px 8vw;
}
.pathbar .path-title{
  font-size:12px;letter-spacing:.16em;color:var(--text-dark-dim);
  text-transform:uppercase;margin-bottom:18px;text-align:center;
}
.pathbar .path-flow{
  display:flex;align-items:center;justify-content:center;
  gap:0;flex-wrap:wrap;
}
.pathbar .step{
  display:flex;align-items:center;gap:10px;
  padding:8px 18px;border-radius:30px;
  background:var(--paper-card);border:1px solid var(--line);
  font-size:13px;color:var(--text-dark);cursor:pointer;
  transition:all .2s ease;
}
.pathbar .step:hover{border-color:var(--brass);transform:translateY(-2px);box-shadow:var(--shadow);}
.pathbar .step .dot{
  width:8px;height:8px;border-radius:50%;
}
.pathbar .step{font-size:12px;padding:7px 14px;}
.pathbar .step[data-ch="onboarding"] .dot{background:var(--teal);}
.pathbar .step[data-ch="foundations"] .dot{background:var(--teal);}
.pathbar .step[data-ch="core"] .dot{background:var(--brass);}
.pathbar .step[data-ch="abstractions"] .dot{background:var(--rust);}
.pathbar .step[data-ch="collections"] .dot{background:var(--teal);}
.pathbar .step[data-ch="memory"] .dot{background:var(--rust);}
.pathbar .step[data-ch="concurrency"] .dot{background:#8b5cf6;}
.pathbar .step[data-ch="async"] .dot{background:#8b5cf6;}
.pathbar .step[data-ch="engineering"] .dot{background:var(--rust);}
.pathbar .sep{color:var(--text-dark-faint);padding:0 6px;font-size:12px;}

/* ============ 章节区通用 ============ */
section.chapters{padding:80px 8vw;}
.ch-head{max-width:1200px;margin:0 auto 44px;}
.ch-head .ch-eyebrow{
  font-size:12px;letter-spacing:.18em;font-weight:700;
  text-transform:uppercase;margin-bottom:12px;
  display:flex;align-items:center;gap:12px;
}
.ch-head .ch-eyebrow .bar{width:36px;height:2px;}
.ch-head h2{
  font-size:clamp(26px,3.2vw,38px);font-weight:700;
  margin-bottom:12px;color:var(--text-dark);
}
.ch-head .ch-desc{font-size:15px;color:var(--text-dark-dim);max-width:640px;}

/* 篇章配色 */
.ch-onboarding .ch-eyebrow{color:var(--teal);}
.ch-onboarding .ch-eyebrow .bar{background:var(--teal);}
.ch-foundations .ch-eyebrow{color:var(--teal);}
.ch-foundations .ch-eyebrow .bar{background:var(--teal);}
.ch-core  .ch-eyebrow{color:var(--brass);}
.ch-core  .ch-eyebrow .bar{background:var(--brass);}
.ch-abstractions .ch-eyebrow{color:var(--rust);}
.ch-abstractions .ch-eyebrow .bar{background:var(--rust);}
.ch-collections .ch-eyebrow{color:var(--teal);}
.ch-collections .ch-eyebrow .bar{background:var(--teal);}
.ch-memory .ch-eyebrow{color:var(--rust);}
.ch-memory .ch-eyebrow .bar{background:var(--rust);}
.ch-concurrency .ch-eyebrow{color:#8b5cf6;}
.ch-concurrency .ch-eyebrow .bar{background:#8b5cf6;}
.ch-async .ch-eyebrow{color:#8b5cf6;}
.ch-async .ch-eyebrow .bar{background:#8b5cf6;}
.ch-engineering .ch-eyebrow{color:var(--rust);}
.ch-engineering .ch-eyebrow .bar{background:var(--rust);}

/* ============ 卡片网格 ============ */
.grid{
  display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));
  gap:20px;max-width:1200px;margin:0 auto;
}
.card{
  background:var(--paper-card);border-radius:14px;padding:24px;
  border:1px solid var(--line);box-shadow:var(--shadow);
  cursor:pointer;transition:all .28s cubic-bezier(.4,0,.2,1);
  position:relative;overflow:hidden;display:flex;flex-direction:column;
}
.card::before{
  content:'';position:absolute;left:0;top:0;bottom:0;width:3px;
  background:transparent;transition:background .28s ease;
}
.card:hover{
  transform:translateY(-4px);
  border-color:rgba(201,149,44,0.45);
  box-shadow:var(--shadow-hover);
}
.card:hover::before{background:var(--brass);}
.card .ic{
  font-size:34px;margin-bottom:14px;
  display:inline-block;transition:transform .28s ease;
}
.card:hover .ic{transform:scale(1.12);}
.card .name{
  font-size:18px;font-weight:700;margin-bottom:4px;
  font-family:'Noto Serif SC',serif;color:var(--text-dark);
}
.card .en{font-size:12px;color:var(--text-dark-faint);font-family:'JetBrains Mono',monospace;margin-bottom:14px;}
.card .analogy{
  display:inline-flex;align-items:center;gap:6px;
  padding:5px 12px;border-radius:20px;
  background:rgba(201,149,44,0.14);color:var(--brass);
  font-size:12px;margin-bottom:16px;align-self:flex-start;
}
.card .analogy .ai{font-size:13px;}
.card .foot{
  display:flex;justify-content:space-between;align-items:center;
  margin-top:auto;padding-top:14px;border-top:1px dashed var(--line);
  font-size:12px;color:var(--text-dark-dim);
}
.card .diff{letter-spacing:2px;}
.card .diff .on{color:var(--brass);}
.card .diff .off{color:var(--text-dark-faint);opacity:.4;}
.card .time{display:flex;align-items:center;gap:5px;}
/* 状态标记 */
.card .status{
  position:absolute;top:16px;right:16px;
  font-size:10px;padding:3px 9px;border-radius:20px;
  font-weight:700;letter-spacing:.04em;
}
.card .status.done{background:rgba(47,138,118,0.16);color:var(--teal);}
.card .status.soon{background:rgba(201,149,44,0.18);color:var(--brass);}
.card .status.plan{background:rgba(90,90,90,0.10);color:var(--text-dark-faint);}
.card.disabled{opacity:.62;}
.card.disabled:hover{transform:none;border-color:var(--line);}

/* 篇章配色 - 卡片左边条 hover */
.ch-onboarding .card:hover::before{background:var(--teal);}
.ch-foundations .card:hover::before{background:var(--teal);}
.ch-abstractions .card:hover::before{background:var(--rust);}
.ch-collections .card:hover::before{background:var(--teal);}
.ch-memory .card:hover::before{background:var(--rust);}
.ch-concurrency .card:hover::before{background:#8b5cf6;}
.ch-async .card:hover::before{background:#8b5cf6;}
.ch-engineering .card:hover::before{background:var(--rust);}

/* ============ 使命区 ============ */
.mission{
  background:var(--paper-soft);color:var(--text-dark);
  padding:100px 8vw;text-align:center;
  border-top:1px solid var(--line);border-bottom:1px solid var(--line);
}
.mission .eyebrow{
  font-size:12px;letter-spacing:.18em;color:var(--rust);
  font-weight:700;margin-bottom:18px;text-transform:uppercase;
}
.mission h2{
  font-size:clamp(28px,4vw,46px);font-weight:700;
  max-width:760px;margin:0 auto 28px;line-height:1.3;
}
.mission .quote{
  font-size:clamp(16px,1.8vw,22px);color:var(--text-dark-dim);
  max-width:560px;margin:0 auto 36px;font-style:italic;
}
.mission .pillars{
  display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));
  gap:24px;max-width:920px;margin:0 auto;
}
.mission .pillar{
  background:var(--paper-card);border-radius:14px;padding:28px 22px;
  box-shadow:0 8px 20px rgba(40,30,10,.08);border:1px solid rgba(0,0,0,0.06);
}
.mission .pillar .pi{font-size:32px;margin-bottom:12px;}
.mission .pillar h4{font-size:16px;margin-bottom:8px;font-family:'Noto Serif SC',serif;}
.mission .pillar p{font-size:13px;color:var(--text-dark-dim);line-height:1.6;}

/* ============ 底部 ============ */
footer{
  background:var(--paper-soft);border-top:1px solid var(--line);
  padding:50px 8vw 36px;text-align:center;color:var(--text-dark-dim);font-size:13px;
}
footer .ft-links{display:flex;gap:18px;justify-content:center;flex-wrap:wrap;margin-bottom:18px;}
footer .ft-links a{color:var(--text-dark-dim);cursor:pointer;}
footer .ft-links a:hover{color:var(--brass);}
footer .ft-brand{
  font-family:'Noto Serif SC',serif;color:var(--brass);
  font-size:15px;font-weight:700;margin-bottom:8px;
}
footer .copy{font-size:11.5px;color:var(--text-dark-faint);}

/* ============ 响应式 ============ */
@media (max-width:760px){
  .topbar nav{display:none;}
  .hero{padding:100px 6vw 60px;}
  .hero .stats{gap:30px;}
  .pathbar .step{padding:6px 12px;font-size:12px;}
  .pathbar .sep{display:none;}
  section.chapters{padding:60px 6vw;}
  .grid{grid-template-columns:1fr;}
}
@media (prefers-reduced-motion:reduce){
  *{animation-duration:.01ms !important;transition-duration:.01ms !important;}
}