/* =============================================================
   usdtzq.com — USDT数字资产品牌 (科技冰蓝风)
   配色: 极地冰蓝 #1a5276 / 霓虹青 #00b894 / 太空灰 #2d3436 / 月光白 #f8f9fa
   字体: Inter (英文) + Noto Sans SC (中文)
   气质: 科技感、数字资产、透明可信、现代轻奢
   ============================================================= */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&family=Noto+Sans+SC:wght@400;500;700&display=swap');

:root {
  --ice: #1a5276;
  --ice-dark: #0e3650;
  --ice-light: #2a7aa6;
  --neon: #00b894;
  --neon-dark: #009977;
  --neon-light: #55d6b0;
  --space: #2d3436;
  --space-light: #3d4446;
  --moon: #f8f9fa;
  --moon-dark: #e9ecef;
  --text: #1a1a2e;
  --text-light: #6c757d;
  --white: #fff;
  --font-en: 'Inter', 'SF Pro', sans-serif;
  --font-cn: 'Noto Sans SC', 'PingFang SC', sans-serif;
  --shadow: 0 2px 16px rgba(0,0,0,0.06);
  --shadow-lg: 0 8px 32px rgba(0,0,0,0.1);
  --radius: 16px;
  --radius-sm: 8px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

body {
  font-family: var(--font-cn);
  color: var(--text);
  background: var(--moon);
  line-height: 1.7;
  font-size: 15px;
  -webkit-font-smoothing: antialiased;
}

.container { max-width: 1200px; margin: 0 auto; padding: 0 24px; }
a { text-decoration: none; color: inherit; }
img { max-width: 100%; }

h1, h2, h3, h4 { font-weight: 700; line-height: 1.2; }

/* ── Buttons ── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 36px;
  font-family: var(--font-en);
  font-size: 14px;
  font-weight: 600;
  border: none;
  cursor: pointer;
  transition: all 0.3s ease;
  border-radius: 60px;
}
.btn-primary {
  background: linear-gradient(135deg, var(--neon), var(--neon-dark));
  color: var(--white);
}
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 8px 30px rgba(0,184,148,0.35); }
.btn-ice {
  background: linear-gradient(135deg, var(--ice), var(--ice-dark));
  color: var(--white);
}
.btn-ice:hover { transform: translateY(-2px); box-shadow: 0 8px 30px rgba(26,82,118,0.3); }
.btn-ghost {
  background: transparent;
  color: var(--ice);
  border: 2px solid var(--neon);
}
.btn-ghost:hover { background: var(--neon); color: var(--white); border-color: var(--neon); transform: translateY(-2px); }

/* ── Section ── */
.section { padding: 100px 0; }
.section-dark { background: var(--space); color: var(--white); }
.section-title {
  text-align: center;
  font-size: 34px;
  margin-bottom: 8px;
  font-weight: 700;
}
.section-title .n { color: var(--neon); }
.section-title .i { color: var(--ice); }
.section-title .tag {
  display: inline-block;
  background: rgba(0,184,148,0.1);
  padding: 4px 16px;
  border-radius: 60px;
  font-size: 12px;
  font-weight: 500;
  color: var(--neon);
  vertical-align: middle;
  margin-left: 8px;
}
.section-title::after {
  content: '';
  display: block;
  width: 50px;
  height: 3px;
  background: linear-gradient(90deg, var(--neon), var(--ice));
  margin: 14px auto 0;
  border-radius: 3px;
}
.section-subtitle {
  text-align: center;
  color: var(--text-light);
  font-size: 14px;
  margin-bottom: 50px;
  font-weight: 400;
}
.section-dark .section-subtitle { color: rgba(255,255,255,0.4); }

/* ── Glass Card Utility ── */
.glass { backdrop-filter: blur(16px); -webkit-backdrop-filter: blur(16px); }

/* ── Navigation ── */
.navbar {
  position: fixed; top: 0; width: 100%; z-index: 1000;
  background: rgba(45,52,54,0.92);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid rgba(0,184,148,0.1);
  transition: all 0.3s;
}
.navbar .container { display: flex; align-items: center; justify-content: space-between; height: 68px; }
.navbar-brand { display: flex; align-items: center; gap: 10px; }
.logo-icon {
  width: 32px; height: 32px;
  background: linear-gradient(135deg, var(--neon), var(--neon-dark));
  color: var(--white);
  font-family: var(--font-en);
  font-weight: 800;
  font-size: 12px;
  display: flex;
  align-items: center; justify-content: center;
  border-radius: 8px;
}
.logo-text { font-size: 20px; font-weight: 700; font-family: var(--font-en); color: var(--white); letter-spacing: 1px; }
.logo-accent { color: var(--neon); font-weight: 700; }

.navbar-links { display: flex; list-style: none; gap: 2px; }
.navbar-links a {
  color: rgba(255,255,255,0.5);
  padding: 8px 16px;
  font-size: 13px;
  font-family: var(--font-en);
  font-weight: 500;
  transition: all 0.3s;
  border-radius: 30px;
}
.navbar-links a:hover, .navbar-links a.active { color: var(--white); background: rgba(0,184,148,0.1); }
.navbar-links .btn-nav {
  background: linear-gradient(135deg, var(--neon), var(--neon-dark));
  color: var(--white); padding: 8px 22px; border-radius: 60px;
  font-weight: 600;
}
.navbar-links .btn-nav:hover { opacity: 0.9; color: var(--white); background: linear-gradient(135deg, var(--neon), var(--neon-dark)); }

.hamburger { display: none; flex-direction: column; gap: 5px; background: none; border: none; cursor: pointer; padding: 5px; }
.hamburger span { display: block; width: 24px; height: 2px; background: var(--white); border-radius: 2px; transition: all 0.3s; }
.nav-overlay {
  display: none; position: fixed; top: 68px; left: 0; width: 100%; height: calc(100vh - 68px);
  background: rgba(45,52,54,0.97); z-index: 999;
  flex-direction: column; align-items: center; justify-content: center; gap: 16px;
}
.nav-overlay a { color: rgba(255,255,255,0.6); font-size: 17px; font-weight: 500; transition: color 0.3s; }
.nav-overlay a:hover { color: var(--neon); }
.nav-overlay.open { display: flex; }

/* ── Hero ── */
.hero {
  position: relative; min-height: 100vh;
  display: flex; align-items: center; justify-content: center; overflow: hidden;
  background: var(--space);
}
.hero::before {
  content: ''; position: absolute; inset: 0;
  background:
    radial-gradient(ellipse at 25% 35%, rgba(0,184,148,0.1) 0%, transparent 45%),
    radial-gradient(ellipse at 75% 65%, rgba(26,82,118,0.15) 0%, transparent 45%);
}
.hero-grid {
  position: absolute; inset: 0;
  background-image:
    linear-gradient(rgba(0,184,148,0.02) 1px, transparent 1px),
    linear-gradient(90deg, rgba(0,184,148,0.02) 1px, transparent 1px);
  background-size: 60px 60px;
}
.hero-content { position: relative; z-index: 2; text-align: center; max-width: 800px; padding: 0 20px; }
.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 20px;
  background: rgba(0,184,148,0.1);
  color: var(--neon);
  font-size: 12px;
  font-weight: 500;
  font-family: var(--font-en);
  border-radius: 60px;
  margin-bottom: 28px;
}
.hero-badge .dot { width: 6px; height: 6px; background: var(--neon); border-radius: 50%; animation: pulse 2s infinite; }
@keyframes pulse { 0%,100%{opacity:1} 50%{opacity:0.3} }
.hero h1 {
  font-size: 52px;
  color: var(--white);
  font-family: var(--font-en);
  font-weight: 800;
  letter-spacing: -1px;
  margin-bottom: 16px;
  line-height: 1.1;
}
.hero h1 span { background: linear-gradient(135deg, var(--neon), var(--ice-light)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }
.hero h1 .sub { font-size: 18px; font-weight: 400; display: block; margin-top: 8px; color: rgba(255,255,255,0.4); letter-spacing: 2px; -webkit-text-fill-color: rgba(255,255,255,0.4); }
.hero p { color: rgba(255,255,255,0.45); font-size: 16px; max-width: 520px; margin: 0 auto 32px; line-height: 1.8; }
.hero-buttons { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.hero-stats { display: flex; gap: 40px; justify-content: center; margin-top: 50px; flex-wrap: wrap; }
.hero-stat { text-align: center; }
.hero-stat .num { font-family: var(--font-en); font-size: 32px; font-weight: 800; color: var(--neon); }
.hero-stat .label { font-size: 12px; color: rgba(255,255,255,0.3); margin-top: 4px; }

/* ── Strip ── */
.strip-section {
  background: var(--white);
  padding: 60px 0;
  border-bottom: 1px solid rgba(0,0,0,0.04);
}
.strip-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 30px; max-width: 800px; margin: 0 auto; }
.strip-item { text-align: center; }
.strip-num { font-family: var(--font-en); font-size: 36px; font-weight: 800; background: linear-gradient(135deg, var(--neon), var(--ice)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }
.strip-label { font-size: 12px; color: var(--text-light); margin-top: 6px; }

/* ── Feature Cards ── */
.feature-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 24px; }
.feature-card {
  background: var(--white);
  padding: 36px 28px;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  transition: all 0.4s;
  border: 1px solid rgba(0,0,0,0.03);
  position: relative;
  overflow: hidden;
}
.feature-card .glow {
  position: absolute; top: -40px; right: -40px;
  width: 100px; height: 100px;
  background: radial-gradient(circle, rgba(0,184,148,0.06), transparent);
  border-radius: 50%;
}
.feature-card:hover { transform: translateY(-6px); box-shadow: var(--shadow-lg); border-color: rgba(0,184,148,0.1); }
.feature-card .icon { font-size: 32px; margin-bottom: 16px; display: block; }
.feature-card .icon-bg {
  display: inline-flex; width: 48px; height: 48px;
  background: rgba(0,184,148,0.08);
  border-radius: 14px;
  align-items: center; justify-content: center;
  font-size: 22px;
  margin-bottom: 16px;
}
.feature-card h3 { font-size: 18px; margin-bottom: 8px; font-weight: 700; color: var(--space); }
.feature-card h3 .en { display: block; font-size: 12px; font-weight: 400; color: var(--text-light); margin-top: 2px; }
.feature-card p { color: var(--text-light); font-size: 14px; line-height: 1.8; }

.section-dark .feature-card { background: var(--space-light); border-color: rgba(255,255,255,0.03); }
.section-dark .feature-card:hover { border-color: rgba(0,184,148,0.15); }
.section-dark .feature-card h3 { color: var(--white); }
.section-dark .feature-card p { color: rgba(255,255,255,0.5); }

.benefits-strip { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 20px; max-width: 900px; margin: 0 auto; }
.benefit-item { text-align: center; padding: 28px 20px; }
.benefit-item .bf-icon { font-size: 34px; margin-bottom: 12px; }
.benefit-item h4 { font-size: 16px; margin-bottom: 6px; color: var(--neon); }
.benefit-item p { font-size: 13px; color: rgba(255,255,255,0.45); }

/* ── CTA ── */
.cta-section {
  padding: 90px 0;
  background: linear-gradient(135deg, var(--ice-dark), var(--space));
  text-align: center; color: var(--white);
}
.cta-section::before {
  content: ''; position: absolute; inset: 0;
  background: radial-gradient(ellipse at 50% 0%, rgba(0,184,148,0.06), transparent);
  pointer-events: none;
}
.cta-section h2 { font-size: 36px; font-family: var(--font-en); font-weight: 800; margin-bottom: 12px; letter-spacing: -0.5px; }
.cta-section h2 .n { color: var(--neon); }
.cta-section p { color: rgba(255,255,255,0.4); margin-bottom: 28px; }

/* ── Interlinks ── */
.interlink-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); gap: 12px; }
.interlink-card {
  background: var(--white);
  padding: 20px 14px;
  text-align: center;
  border-radius: var(--radius-sm);
  transition: all 0.3s;
  border: 1px solid rgba(0,0,0,0.03);
}
.interlink-card:hover { transform: translateY(-3px); box-shadow: var(--shadow); border-color: var(--neon); }
.interlink-card .il-icon { font-size: 24px; margin-bottom: 6px; }
.interlink-card h4 { font-size: 12px; font-weight: 600; }
.section-dark .interlink-card { background: var(--space-light); border-color: rgba(255,255,255,0.03); }
.section-dark .interlink-card h4 { color: var(--white); }
.section-dark .interlink-card:hover { background: rgba(0,184,148,0.08); }

/* ── FAQ ── */
.faq-list { max-width: 680px; margin: 0 auto; }
.faq-item {
  background: var(--white);
  border-radius: var(--radius-sm);
  margin-bottom: 8px;
  overflow: hidden;
  border: 1px solid rgba(0,0,0,0.03);
  transition: all 0.3s;
}
.faq-item.active { border-color: var(--neon); }
.faq-question {
  padding: 16px 20px; cursor: pointer;
  font-size: 14px; font-weight: 500;
  display: flex; justify-content: space-between; align-items: center;
  transition: background 0.2s;
}
.faq-item.active .faq-question { color: var(--neon); }
.faq-question .arrow { transition: transform 0.3s; font-size: 14px; color: var(--text-light); }
.faq-item.active .arrow { transform: rotate(180deg); color: var(--neon); }
.faq-answer { max-height: 0; overflow: hidden; transition: max-height 0.3s ease; }
.faq-item.active .faq-answer { max-height: 500px; }
.faq-answer p { padding: 0 20px 16px; color: var(--text-light); font-size: 14px; line-height: 1.8; }

/* ── Footer ── */
.footer {
  background: var(--space);
  color: rgba(255,255,255,0.4);
  padding: 60px 0 30px;
  border-top: 1px solid rgba(0,184,148,0.06);
}
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 40px; margin-bottom: 40px; }
.footer-brand h3 { font-size: 20px; font-family: var(--font-en); color: var(--white); margin-bottom: 12px; letter-spacing: 1px; }
.footer-brand p { font-size: 13px; line-height: 1.9; }
.footer h4 { font-size: 13px; color: var(--neon); margin-bottom: 14px; font-weight: 600; }
.footer ul { list-style: none; }
.footer ul li { margin-bottom: 8px; }
.footer ul li a { font-size: 13px; transition: color 0.3s; }
.footer ul li a:hover { color: var(--neon); }
.footer-bottom { border-top: 1px solid rgba(255,255,255,0.04); padding-top: 24px; text-align: center; font-size: 12px; }

/* ── Page Hero ── */
.page-hero {
  padding: 130px 0 60px;
  background: linear-gradient(135deg, var(--space), var(--ice-dark));
  color: var(--white);
  text-align: center;
  position: relative;
}
.page-hero::after {
  content: ''; position: absolute; bottom: 0; left: 0; right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--neon), var(--ice), var(--neon));
}
.page-hero h1 { font-size: 40px; font-family: var(--font-en); font-weight: 800; letter-spacing: -0.5px; }
.page-hero h1 span { background: linear-gradient(135deg, var(--neon), var(--ice-light)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }
.page-hero p { color: rgba(255,255,255,0.4); margin-top: 12px; font-size: 14px; }
.page-hero .breadcrumb { margin-top: 14px; font-size: 12px; }
.page-hero .breadcrumb a { color: rgba(255,255,255,0.3); }
.page-hero .breadcrumb a:hover { color: var(--neon); }
.page-hero .breadcrumb span { color: var(--neon); }
.page-hero-stats { display: flex; gap: 36px; justify-content: center; margin-top: 32px; flex-wrap: wrap; }
.page-hero-stats .ps-item { text-align: center; }
.page-hero-stats .ps-num { font-family: var(--font-en); font-size: 28px; font-weight: 800; color: var(--neon); }
.page-hero-stats .ps-label { font-size: 11px; color: rgba(255,255,255,0.3); margin-top: 4px; }

/* ── Content Layouts ── */

/* Content Split */
.content-split { display: grid; grid-template-columns: 1fr 1fr; gap: 50px; align-items: center; }
.content-split.reverse { direction: rtl; }
.content-split.reverse > * { direction: ltr; }
.content-split .text h2 { font-size: 30px; margin-bottom: 14px; font-weight: 700; }
.content-split .text h2 .n { color: var(--neon); }
.content-split .text p { color: var(--text-light); margin-bottom: 14px; line-height: 1.9; font-size: 15px; }
.content-split .visual {
  background: linear-gradient(135deg, rgba(0,184,148,0.04), rgba(26,82,118,0.06));
  border-radius: var(--radius);
  padding: 60px 40px;
  text-align: center;
  border: 1px solid rgba(0,184,148,0.06);
}
.content-split .visual .vs-icon { font-size: 60px; margin-bottom: 16px; display: block; }
.content-split .visual h3 { font-family: var(--font-en); font-weight: 700; color: var(--neon); font-size: 18px; }
.content-split .visual p { color: var(--text-light); margin-top: 8px; font-size: 13px; }

/* Timeline */
.timeline { max-width: 650px; margin: 0 auto; position: relative; }
.timeline::before {
  content: ''; position: absolute; left: 18px; top: 0; bottom: 0;
  width: 2px;
  background: linear-gradient(180deg, var(--neon), var(--ice));
}
.tl-item { padding-left: 52px; margin-bottom: 36px; position: relative; }
.tl-item::before {
  content: ''; position: absolute; left: 10px; top: 4px;
  width: 18px; height: 18px;
  background: var(--neon); border-radius: 50%;
  border: 3px solid var(--moon);
}
.tl-item h3 { font-size: 18px; margin-bottom: 6px; }
.tl-item h3 .year { color: var(--neon); font-weight: 700; margin-right: 8px; font-family: var(--font-en); }
.tl-item p { color: var(--text-light); font-size: 14px; }
.tl-item ul { margin-top: 6px; }
.tl-item ul li { list-style: none; color: var(--text-light); font-size: 14px; margin-bottom: 4px; padding-left: 16px; position: relative; }
.tl-item ul li::before { content: '—'; position: absolute; left: 0; color: var(--neon); }

/* Table */
.comp-table { width: 100%; border-collapse: collapse; font-size: 14px; }
.comp-table th, .comp-table td { padding: 14px 18px; text-align: left; border-bottom: 1px solid rgba(0,0,0,0.04); }
.comp-table th { background: var(--space); color: var(--neon); font-family: var(--font-en); font-weight: 600; font-size: 13px; }
.comp-table tr:hover td { background: rgba(0,184,148,0.02); }
.comp-table .tag { display: inline-block; padding: 2px 12px; border-radius: 60px; font-size: 11px; font-weight: 600; }
.comp-table .tag.neon { background: var(--neon); color: var(--white); }
.comp-table .tag.ice { background: var(--ice); color: var(--white); }
.comp-table .tag.moon { background: var(--moon-dark); color: var(--space); }

/* Feature List */
.feature-list { max-width: 700px; margin: 0 auto; }
.fl-item { display: flex; gap: 18px; padding: 22px 0; border-bottom: 1px solid rgba(0,0,0,0.03); }
.fl-item:last-child { border-bottom: none; }
.fl-icon { font-size: 24px; min-width: 40px; text-align: center; }
.fl-text h4 { font-size: 16px; margin-bottom: 4px; }
.fl-text p { color: var(--text-light); font-size: 14px; }

/* Card Grid */
.card-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 20px; }
.card-grid .card {
  background: var(--white);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
  transition: all 0.4s;
}
.card-grid .card:hover { transform: translateY(-5px); box-shadow: var(--shadow-lg); }
.card .card-body { padding: 28px; }
.card .card-body h3 { font-size: 17px; margin-bottom: 8px; }
.card .card-body p { color: var(--text-light); font-size: 14px; line-height: 1.8; }
.card .card-header { padding: 32px; text-align: center; font-size: 36px; background: linear-gradient(135deg, rgba(0,184,148,0.04), rgba(26,82,118,0.04)); }
.section-dark .card-grid .card { background: var(--space-light); border: 1px solid rgba(255,255,255,0.02); }
.section-dark .card .card-header { background: rgba(0,184,148,0.04); }
.section-dark .card .card-body h3 { color: var(--white); }
.section-dark .card .card-body p { color: rgba(255,255,255,0.5); }

/* Steps */
.steps { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 20px; counter-reset: step; }
.step {
  text-align: center; padding: 30px 22px;
  background: var(--white); border-radius: var(--radius); box-shadow: var(--shadow);
  position: relative;
}
.step::before {
  counter-increment: step;
  content: "0" counter(step);
  position: absolute; top: -6px; right: 20px;
  font-family: var(--font-en);
  font-size: 48px;
  font-weight: 800;
  color: rgba(0,184,148,0.06);
  line-height: 1;
}
.step .s-icon { font-size: 32px; margin-bottom: 12px; }
.step h4 { font-size: 15px; margin-bottom: 6px; }
.step p { color: var(--text-light); font-size: 13px; }

/* ── Responsive ── */
@media (max-width: 900px) {
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .content-split { grid-template-columns: 1fr; gap: 30px; }
  .hero-stats { gap: 24px; }
  .hero h1 { font-size: 38px; }
  .strip-grid { grid-template-columns: repeat(2, 1fr); gap: 16px; }
}
@media (max-width: 768px) {
  .navbar-links { display: none; }
  .hamburger { display: flex; }
  .hero h1 { font-size: 30px; }
  .hero h1 .sub { font-size: 14px; }
  .hero { min-height: 80vh; }
  .hero-stat .num { font-size: 22px; }
  .section { padding: 60px 0; }
  .section-title { font-size: 26px; }
  .feature-grid { grid-template-columns: 1fr; }
  .page-hero h1 { font-size: 28px; }
  .page-hero { padding: 110px 0 40px; }
  .footer-grid { grid-template-columns: 1fr; gap: 24px; }
  .steps { grid-template-columns: 1fr; }
  .card-grid { grid-template-columns: 1fr; }
  .benefits-strip { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 480px) {
  .strip-grid { grid-template-columns: 1fr 1fr; }
  .hero h1 { font-size: 24px; }
  .benefits-strip { grid-template-columns: 1fr; }
  .interlink-grid { grid-template-columns: repeat(2, 1fr); }
}