/* ============================================================
   FB Ads Lab · 主样式
   设计：黑金 + 深蓝科技 + 玻璃卡片
   作者：FB Ads Lab
   ============================================================ */

:root{
  /* 颜色系统 */
  --bg-deep: #07090f;
  --bg-1: #0c1018;
  --bg-2: #131826;
  --bg-3: #1a2030;
  --line: rgba(255,255,255,.08);
  --line-strong: rgba(255,255,255,.16);

  --ink: #e8ecf4;
  --ink-soft: #aab3c5;
  --ink-mute: #6b7488;

  --gold: #d4a857;
  --gold-soft: #b8924a;
  --gold-glow: rgba(212,168,87,.18);
  --blue: #3b82f6;
  --blue-deep: #1e40af;
  --blue-glow: rgba(59,130,246,.16);
  --cyan: #38bdf8;
  --green: #34d399;
  --red: #f87171;

  /* 度量 */
  --r-sm: 8px;
  --r: 14px;
  --r-lg: 20px;
  --maxw: 1240px;
  --shadow: 0 1px 0 rgba(255,255,255,.04) inset, 0 20px 50px -25px rgba(0,0,0,.7);
  --shadow-card: 0 1px 0 rgba(255,255,255,.04) inset, 0 12px 32px -16px rgba(0,0,0,.6);

  /* 字体 */
  --sans: "Manrope", -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", sans-serif;
  --serif: "Noto Serif SC", "Songti SC", serif;
  --mono: "JetBrains Mono", "SF Mono", Consolas, monospace;
}

*{margin:0;padding:0;box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%;scroll-padding-top:80px}
body{
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.7;
  color: var(--ink);
  background: var(--bg-deep);
  background-image:
    radial-gradient(ellipse at top left, rgba(59,130,246,.08), transparent 50%),
    radial-gradient(ellipse at bottom right, rgba(212,168,87,.05), transparent 50%);
  background-attachment: fixed;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}
img{max-width:100%;display:block}
a{color: inherit; text-decoration: none}
button{font: inherit; cursor: pointer; border: none; background: none; color: inherit}
ul,ol{list-style: none}

/* 选中颜色 */
::selection{background: var(--gold); color: var(--bg-deep)}

/* 滚动条 */
::-webkit-scrollbar{width: 10px; height: 10px}
::-webkit-scrollbar-track{background: var(--bg-1)}
::-webkit-scrollbar-thumb{background: var(--bg-3); border-radius: 5px}
::-webkit-scrollbar-thumb:hover{background: var(--gold-soft)}

/* ============================================================
   工具类
   ============================================================ */
.container{max-width: var(--maxw); margin: 0 auto; padding: 0 24px}
.gold{color: var(--gold)}
.blue{color: var(--blue)}
.text-soft{color: var(--ink-soft)}
.text-mute{color: var(--ink-mute)}
.mono{font-family: var(--mono)}
.center{text-align: center}

/* ============================================================
   顶部导航
   ============================================================ */
.site-header{
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(7, 9, 15, .78);
  backdrop-filter: blur(16px) saturate(140%);
  -webkit-backdrop-filter: blur(16px) saturate(140%);
  border-bottom: 1px solid var(--line);
  transition: box-shadow .25s;
}
.site-header.scrolled{
  box-shadow: 0 8px 32px -16px rgba(0,0,0,.8);
}
.nav-wrap{
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 14px 24px;
  display: flex;
  align-items: center;
  gap: 28px;
}
.logo{
  display: flex;
  align-items: center;
  gap: 10px;
  flex-shrink: 0;
}
.logo-mark{
  width: 36px; height: 36px;
  display: grid; place-items: center;
  background: linear-gradient(135deg, var(--gold), var(--gold-soft));
  color: var(--bg-deep);
  border-radius: 10px;
  font-family: var(--serif);
  font-weight: 800;
  font-size: 18px;
  letter-spacing: 0;
  box-shadow: 0 4px 16px var(--gold-glow);
}
.logo-text{
  font-weight: 800;
  font-size: 17px;
  letter-spacing: -.01em;
}
.logo-text small{
  display: block;
  font-family: var(--mono);
  font-size: 10px;
  font-weight: 500;
  color: var(--ink-mute);
  letter-spacing: .15em;
  margin-top: -2px;
}

.primary-nav{
  display: flex;
  gap: 4px;
  margin-left: auto;
  font-size: 14.5px;
  flex-wrap: wrap;
}
.primary-nav a{
  position: relative;
  padding: 8px 14px;
  border-radius: 8px;
  color: var(--ink-soft);
  transition: color .2s, background .2s;
  white-space: nowrap;
}
.primary-nav a:hover{color: var(--ink); background: rgba(255,255,255,.04)}
.primary-nav a.active{color: var(--gold)}

.nav-cta{
  flex-shrink: 0;
  background: linear-gradient(135deg, var(--gold), var(--gold-soft));
  color: var(--bg-deep);
  padding: 10px 18px;
  border-radius: 999px;
  font-size: 14px;
  font-weight: 700;
  transition: transform .2s, box-shadow .2s;
  white-space: nowrap;
}
.nav-cta:hover{
  transform: translateY(-1px);
  box-shadow: 0 8px 24px var(--gold-glow);
}

/* 移动端菜单按钮 */
.nav-toggle{
  display: none;
  width: 40px; height: 40px;
  align-items: center; justify-content: center;
  border-radius: 8px;
  background: rgba(255,255,255,.04);
  margin-left: auto;
}
.nav-toggle span{
  display: block;
  width: 18px; height: 2px;
  background: var(--ink);
  position: relative;
  transition: transform .25s;
}
.nav-toggle span::before,
.nav-toggle span::after{
  content: ""; position: absolute; left: 0;
  width: 100%; height: 2px;
  background: var(--ink);
  transition: transform .25s, top .25s;
}
.nav-toggle span::before{top: -6px}
.nav-toggle span::after{top: 6px}
.nav-toggle.open span{background: transparent}
.nav-toggle.open span::before{top: 0; transform: rotate(45deg)}
.nav-toggle.open span::after{top: 0; transform: rotate(-45deg)}

/* ============================================================
   按钮
   ============================================================ */
.btn{
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 26px;
  border-radius: 999px;
  font-weight: 700;
  font-size: 15px;
  transition: all .25s;
  border: 1px solid transparent;
  cursor: pointer;
}
.btn-primary{
  background: linear-gradient(135deg, var(--gold), var(--gold-soft));
  color: var(--bg-deep);
}
.btn-primary:hover{
  transform: translateY(-2px);
  box-shadow: 0 12px 32px var(--gold-glow);
}
.btn-ghost{
  background: rgba(255,255,255,.04);
  color: var(--ink);
  border-color: var(--line-strong);
}
.btn-ghost:hover{
  background: rgba(255,255,255,.08);
  border-color: var(--gold);
  color: var(--gold);
}
.btn-blue{
  background: linear-gradient(135deg, var(--blue), var(--blue-deep));
  color: white;
}
.btn-blue:hover{
  transform: translateY(-2px);
  box-shadow: 0 12px 32px var(--blue-glow);
}
.btn-lg{padding: 18px 34px; font-size: 16px}

/* ============================================================
   通用区块标题
   ============================================================ */
.section{padding: 96px 0}
.section-head{
  max-width: 760px;
  margin: 0 auto 56px;
  text-align: center;
  padding: 0 24px;
}
.section-head .kicker{
  display: inline-block;
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: .2em;
  color: var(--gold);
  margin-bottom: 14px;
  text-transform: uppercase;
  padding: 6px 14px;
  border: 1px solid var(--gold-soft);
  border-radius: 999px;
  background: var(--gold-glow);
}
.section-head h2{
  font-size: clamp(28px, 4vw, 44px);
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -.02em;
  margin-bottom: 16px;
}
.section-head h2 em{
  font-style: normal;
  background: linear-gradient(135deg, var(--gold), #f0c97a);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.section-head .lead{
  color: var(--ink-soft);
  font-size: 17px;
  line-height: 1.7;
}

/* ============================================================
   Hero 首屏
   ============================================================ */
.hero{
  position: relative;
  padding: 80px 0 100px;
  overflow: hidden;
}
.hero::before{
  content: "";
  position: absolute;
  top: -200px; right: -200px;
  width: 600px; height: 600px;
  background: radial-gradient(circle, var(--blue-glow), transparent 60%);
  filter: blur(40px);
}
.hero::after{
  content: "";
  position: absolute;
  bottom: -200px; left: -200px;
  width: 500px; height: 500px;
  background: radial-gradient(circle, var(--gold-glow), transparent 60%);
  filter: blur(40px);
}
.hero-grid{
  position: relative;
  display: grid;
  grid-template-columns: 1.15fr 1fr;
  gap: 56px;
  align-items: center;
}
.hero-eyebrow{
  display: inline-flex;
  align-items: center;
  gap: 10px;
  background: rgba(255,255,255,.04);
  border: 1px solid var(--line-strong);
  padding: 8px 16px;
  border-radius: 999px;
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: .1em;
  color: var(--ink-soft);
  margin-bottom: 28px;
}
.hero-eyebrow .pulse{
  width: 8px; height: 8px;
  background: var(--green);
  border-radius: 50%;
  box-shadow: 0 0 0 4px rgba(52,211,153,.18);
  animation: pulse 2s infinite;
}
@keyframes pulse{
  0%,100%{box-shadow: 0 0 0 4px rgba(52,211,153,.18)}
  50%{box-shadow: 0 0 0 10px rgba(52,211,153,0)}
}

.hero h1{
  font-size: clamp(34px, 5.2vw, 60px);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -.025em;
  margin-bottom: 22px;
}
.hero h1 .accent{
  background: linear-gradient(135deg, var(--gold) 0%, #f0c97a 50%, var(--gold) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  position: relative;
  display: inline-block;
}
.hero h1 .accent::after{
  content: "";
  position: absolute;
  left: 0; right: 0; bottom: -4px;
  height: 3px;
  background: linear-gradient(90deg, transparent, var(--gold), transparent);
  opacity: .6;
}
.hero-sub{
  font-size: 17px;
  color: var(--ink-soft);
  line-height: 1.75;
  margin-bottom: 36px;
  max-width: 540px;
}
.hero-cta{
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  margin-bottom: 40px;
}
.hero-tags{
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  font-family: var(--mono);
  font-size: 12px;
}
.hero-tags span{
  padding: 5px 12px;
  background: rgba(255,255,255,.03);
  border: 1px solid var(--line);
  border-radius: 4px;
  color: var(--ink-mute);
}

/* Hero 数据看板 */
.hero-dash{
  position: relative;
  background: linear-gradient(160deg, rgba(255,255,255,.04), rgba(255,255,255,.01));
  border: 1px solid var(--line-strong);
  border-radius: var(--r-lg);
  padding: 24px;
  box-shadow: var(--shadow);
  backdrop-filter: blur(20px);
}
.dash-head{
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--line);
  margin-bottom: 20px;
}
.dash-title{
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: .12em;
  color: var(--ink-soft);
  text-transform: uppercase;
}
.dash-dots{display: flex; gap: 6px}
.dash-dots span{width: 8px; height: 8px; border-radius: 50%; background: var(--bg-3)}
.dash-dots span:nth-child(1){background: #ff5f56}
.dash-dots span:nth-child(2){background: #ffbd2e}
.dash-dots span:nth-child(3){background: #27c93f}

.dash-stats{
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
  margin-bottom: 20px;
}
.dash-stat{
  background: rgba(255,255,255,.03);
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  padding: 14px;
}
.dash-stat .lab{
  font-family: var(--mono);
  font-size: 10px;
  color: var(--ink-mute);
  letter-spacing: .1em;
  text-transform: uppercase;
}
.dash-stat .val{
  font-family: var(--mono);
  font-size: 22px;
  font-weight: 700;
  margin-top: 6px;
  color: var(--gold);
}
.dash-stat .delta{
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-family: var(--mono);
  font-size: 11px;
  color: var(--green);
  margin-top: 2px;
}
.dash-stat .delta.down{color: var(--red)}

.dash-chart{
  height: 140px;
  margin-bottom: 16px;
}

.dash-modules{
  display: grid;
  gap: 8px;
}
.dash-module-row{
  display: grid;
  grid-template-columns: 1fr auto auto;
  gap: 12px;
  align-items: center;
  padding: 10px 12px;
  background: rgba(255,255,255,.02);
  border-radius: var(--r-sm);
  font-family: var(--mono);
  font-size: 12px;
}
.dash-module-row .name{color: var(--ink-soft)}
.dash-module-row .pct{color: var(--gold)}
.dash-module-row .bar{
  width: 80px; height: 4px;
  background: rgba(255,255,255,.06);
  border-radius: 2px;
  overflow: hidden;
}
.dash-module-row .bar i{
  display: block;
  height: 100%;
  background: linear-gradient(90deg, var(--gold), #f0c97a);
}

/* Hero 数据条 */
.hero-stats-bar{
  margin-top: 80px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  padding: 28px 0;
}
.hero-stats-bar > div{
  text-align: center;
  border-right: 1px solid var(--line);
}
.hero-stats-bar > div:last-child{border-right: none}
.hero-stats-bar .num{
  font-family: var(--mono);
  font-size: clamp(28px, 3.5vw, 40px);
  font-weight: 700;
  color: var(--gold);
  line-height: 1;
  letter-spacing: -.02em;
}
.hero-stats-bar .lbl{
  margin-top: 8px;
  font-size: 13px;
  color: var(--ink-mute);
}

/* ============================================================
   模块网格（首页 7 大模块）
   ============================================================ */
.modules-grid{
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 24px;
}
.module-card{
  position: relative;
  background: linear-gradient(160deg, rgba(255,255,255,.04), rgba(255,255,255,.01));
  border: 1px solid var(--line);
  border-radius: var(--r-lg);
  padding: 32px;
  transition: all .3s;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}
.module-card::before{
  content: "";
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--gold), transparent);
  opacity: 0;
  transition: opacity .3s;
}
.module-card:hover{
  transform: translateY(-4px);
  border-color: var(--gold-soft);
  box-shadow: var(--shadow-card);
}
.module-card:hover::before{opacity: 1}

.module-icon{
  width: 56px; height: 56px;
  margin-bottom: 24px;
  border-radius: 14px;
  background: linear-gradient(135deg, var(--blue-glow), transparent);
  border: 1px solid var(--line-strong);
  display: grid;
  place-items: center;
  color: var(--gold);
}
.module-card h3{
  font-size: 22px;
  font-weight: 800;
  letter-spacing: -.01em;
  margin-bottom: 12px;
  line-height: 1.3;
}
.module-card .module-num{
  position: absolute;
  top: 24px; right: 28px;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--ink-mute);
  letter-spacing: .1em;
}
.module-card .module-desc{
  color: var(--ink-soft);
  font-size: 14.5px;
  line-height: 1.7;
  margin-bottom: 20px;
  flex: 1;
}
.module-card .module-points{
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-bottom: 24px;
}
.module-card .module-points li{
  font-size: 13.5px;
  color: var(--ink-soft);
  padding-left: 18px;
  position: relative;
}
.module-card .module-points li::before{
  content: "→";
  position: absolute;
  left: 0;
  color: var(--gold);
}
.module-link{
  font-family: var(--mono);
  font-size: 13px;
  color: var(--gold);
  font-weight: 600;
  letter-spacing: .02em;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: gap .2s;
}
.module-card:hover .module-link{gap: 10px}

/* ============================================================
   学习路径时间线
   ============================================================ */
.path{
  background: linear-gradient(180deg, transparent, rgba(255,255,255,.02));
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}
.path-timeline{
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 24px;
  position: relative;
}
.path-line{
  position: absolute;
  left: 50%;
  top: 0; bottom: 0;
  width: 2px;
  background: linear-gradient(180deg, transparent, var(--gold-soft), transparent);
  transform: translateX(-50%);
}
.path-step{
  position: relative;
  display: grid;
  grid-template-columns: 1fr 100px 1fr;
  gap: 24px;
  align-items: center;
  margin-bottom: 32px;
}
.path-step:last-child{margin-bottom: 0}
.path-step .path-card{
  background: linear-gradient(160deg, rgba(255,255,255,.04), rgba(255,255,255,.01));
  border: 1px solid var(--line);
  border-radius: var(--r);
  padding: 24px 28px;
  transition: all .25s;
}
.path-step:nth-child(odd) .path-card{grid-column: 1}
.path-step:nth-child(even) .path-card{grid-column: 3}
.path-step:nth-child(odd) .path-card{text-align: right}
.path-step .path-card:hover{
  border-color: var(--gold-soft);
  transform: translateY(-2px);
}
.path-step .step-num{
  grid-column: 2;
  width: 48px; height: 48px;
  background: var(--bg-2);
  border: 2px solid var(--gold);
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-family: var(--mono);
  font-weight: 700;
  color: var(--gold);
  margin: 0 auto;
  position: relative;
  z-index: 2;
  box-shadow: 0 0 0 6px var(--bg-deep);
}
.path-card h4{
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 8px;
  color: var(--ink);
}
.path-card p{
  font-size: 14px;
  color: var(--ink-soft);
  line-height: 1.65;
}

/* ============================================================
   适合人群
   ============================================================ */
.audience-grid{
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 24px;
}
.audience-card{
  background: rgba(255,255,255,.02);
  border: 1px solid var(--line);
  border-radius: var(--r);
  padding: 28px 24px;
  text-align: center;
  transition: all .25s;
}
.audience-card:hover{
  background: rgba(255,255,255,.04);
  border-color: var(--gold-soft);
  transform: translateY(-3px);
}
.audience-card .ai{
  font-size: 32px;
  margin-bottom: 16px;
  display: inline-block;
}
.audience-card h4{
  font-size: 17px;
  font-weight: 700;
  margin-bottom: 8px;
}
.audience-card p{
  font-size: 13.5px;
  color: var(--ink-soft);
  line-height: 1.6;
}

/* ============================================================
   FAQ
   ============================================================ */
.faq-list{
  max-width: 880px;
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.faq-item{
  background: rgba(255,255,255,.02);
  border: 1px solid var(--line);
  border-radius: var(--r);
  overflow: hidden;
  transition: border-color .25s;
}
.faq-item[open]{border-color: var(--gold-soft); background: rgba(255,255,255,.04)}
.faq-item summary{
  list-style: none;
  cursor: pointer;
  padding: 22px 28px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  font-size: 16.5px;
  font-weight: 600;
  color: var(--ink);
}
.faq-item summary::-webkit-details-marker{display: none}
.faq-item summary::after{
  content: "+";
  flex-shrink: 0;
  width: 28px; height: 28px;
  display: grid; place-items: center;
  border: 1px solid var(--line-strong);
  border-radius: 50%;
  font-family: var(--mono);
  font-size: 18px;
  color: var(--ink-soft);
  transition: transform .25s, color .25s;
}
.faq-item[open] summary::after{
  transform: rotate(45deg);
  color: var(--gold);
  border-color: var(--gold);
}
.faq-item .faq-body{
  padding: 0 28px 24px;
  font-size: 15px;
  line-height: 1.75;
  color: var(--ink-soft);
}
.faq-item .faq-body p + p{margin-top: 12px}

/* ============================================================
   底部 CTA
   ============================================================ */
.final-cta{
  position: relative;
  padding: 100px 24px;
  text-align: center;
  background:
    radial-gradient(ellipse at 30% 30%, var(--blue-glow), transparent 60%),
    radial-gradient(ellipse at 70% 70%, var(--gold-glow), transparent 60%),
    var(--bg-1);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  overflow: hidden;
}
.final-cta::before{
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(255,255,255,.02) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,.02) 1px, transparent 1px);
  background-size: 40px 40px;
  mask: radial-gradient(ellipse at center, black, transparent 70%);
  -webkit-mask: radial-gradient(ellipse at center, black, transparent 70%);
}
.final-cta-inner{
  position: relative;
  max-width: 760px;
  margin: 0 auto;
}
.final-cta h2{
  font-size: clamp(28px, 4vw, 44px);
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -.02em;
  margin-bottom: 18px;
}
.final-cta p{
  color: var(--ink-soft);
  font-size: 17px;
  margin-bottom: 36px;
  max-width: 560px;
  margin-left: auto; margin-right: auto;
}
.final-cta .cta-row{
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  justify-content: center;
}

/* ============================================================
   底部页脚
   ============================================================ */
.site-footer{
  background: var(--bg-1);
  padding: 64px 0 32px;
  border-top: 1px solid var(--line);
}
.foot-grid{
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr 1fr;
  gap: 48px;
  padding-bottom: 40px;
  border-bottom: 1px solid var(--line);
}
.foot-brand p{
  margin-top: 16px;
  font-size: 14px;
  color: var(--ink-soft);
  line-height: 1.7;
  max-width: 320px;
}
.foot-col h4{
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .15em;
  text-transform: uppercase;
  color: var(--ink-mute);
  margin-bottom: 18px;
  font-weight: 600;
}
.foot-col a{
  display: block;
  font-size: 14px;
  color: var(--ink-soft);
  padding: 5px 0;
  transition: color .2s;
}
.foot-col a:hover{color: var(--gold)}
.foot-bottom{
  margin-top: 28px;
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--ink-mute);
}

/* ============================================================
   返回顶部
   ============================================================ */
.back-top{
  position: fixed;
  right: 28px;
  bottom: 28px;
  width: 44px; height: 44px;
  display: grid; place-items: center;
  background: var(--bg-2);
  border: 1px solid var(--line-strong);
  border-radius: 50%;
  color: var(--ink-soft);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(8px);
  transition: all .25s;
  z-index: 90;
}
.back-top.show{
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.back-top:hover{
  border-color: var(--gold);
  color: var(--gold);
}

/* ============================================================
   响应式
   ============================================================ */
@media (max-width: 1024px){
  .hero-grid{grid-template-columns: 1fr; gap: 40px}
  .modules-grid{grid-template-columns: repeat(2, 1fr)}
  .audience-grid{grid-template-columns: repeat(2, 1fr)}
  .foot-grid{grid-template-columns: 1fr 1fr; gap: 32px}
  .path-line{left: 24px}
  .path-step{
    grid-template-columns: 48px 1fr;
    gap: 20px;
  }
  .path-step .step-num{grid-column: 1; margin: 0}
  .path-step:nth-child(odd) .path-card,
  .path-step:nth-child(even) .path-card{
    grid-column: 2;
    text-align: left;
  }
}

@media (max-width: 720px){
  .section{padding: 64px 0}
  .nav-wrap{padding: 12px 20px; gap: 12px}
  .primary-nav{display: none}
  .nav-toggle{display: flex}
  .nav-cta{padding: 8px 14px; font-size: 13px}

  .hero{padding: 50px 0 70px}
  .hero h1{font-size: 32px}
  .hero-stats-bar{
    grid-template-columns: repeat(2, 1fr);
    gap: 0;
  }
  .hero-stats-bar > div{
    border-bottom: 1px solid var(--line);
    padding: 16px 0;
  }
  .hero-stats-bar > div:nth-child(2){border-right: none}
  .hero-stats-bar > div:nth-child(3),
  .hero-stats-bar > div:nth-child(4){padding-bottom: 0}

  .modules-grid{grid-template-columns: 1fr; padding: 0 20px}
  .audience-grid{grid-template-columns: 1fr; padding: 0 20px}
  .foot-grid{grid-template-columns: 1fr; gap: 28px}
  .foot-bottom{flex-direction: column; text-align: center}
  .container{padding: 0 20px}
  .back-top{right: 16px; bottom: 16px}
  .nav-cta span{display: none}
}

/* 移动端导航抽屉 */
.mobile-nav{
  position: fixed;
  top: 64px; left: 0; right: 0;
  background: var(--bg-1);
  border-bottom: 1px solid var(--line);
  padding: 16px 20px 24px;
  display: none;
  z-index: 99;
  max-height: calc(100vh - 64px);
  overflow-y: auto;
}
.mobile-nav.open{display: block}
.mobile-nav a{
  display: block;
  padding: 12px 14px;
  border-radius: 8px;
  color: var(--ink-soft);
  font-size: 15px;
  border-bottom: 1px solid var(--line);
}
.mobile-nav a:last-child{border-bottom: none}
.mobile-nav a:hover{background: rgba(255,255,255,.04); color: var(--gold)}