/* USTD官方下载 - 安全合规数字资产交易站 */
:root {
  --bg: #0a0f1c;
  --bg2: #0f1526;
  --card: #141c2e;
  --line: rgba(255,255,255,0.08);
  --text: #f5f7fa;
  --muted: #9aa7bd;
  --usdt: #26a17b;
  --blue: #1a56db;
  --gold: #d4a437;
  --btc: #f7931a;
  --white: #ffffff;
  --radius: 14px;
  --shadow: 0 10px 30px rgba(0,0,0,0.35);
}
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { font-family: "Microsoft YaHei", "PingFang SC", Arial, sans-serif; background: var(--bg); color: var(--text); line-height: 1.7; }
.container { max-width: 1200px; margin: 0 auto; padding: 0 20px; }
a { text-decoration: none; color: inherit; }
img { max-width: 100%; display: block; }
ul { list-style: none; }

/* Header */
.site-header { position: sticky; top: 0; z-index: 100; background: rgba(10,15,28,0.92); backdrop-filter: blur(10px); border-bottom: 1px solid var(--line); }
.nav-container { max-width: 1200px; margin: 0 auto; padding: 0 20px; display: flex; align-items: center; justify-content: space-between; height: 68px; }
.brand { font-size: 22px; font-weight: 800; color: var(--white); }
.brand span { color: var(--usdt); }
.nav-links { display: flex; gap: 28px; }
.nav-links a { color: var(--muted); font-size: 15px; transition: color 0.3s; }
.nav-links a:hover, .nav-links a.active { color: var(--usdt); }
.nav-toggle { display: none; background: none; border: 0; color: var(--text); font-size: 26px; cursor: pointer; }

/* Hero */
.hero { padding: 100px 0 80px; text-align: center; background: radial-gradient(circle at 50% 0%, rgba(38,161,123,0.16), transparent 60%), var(--bg); }
.badge { display: inline-block; padding: 6px 16px; border: 1px solid rgba(38,161,123,0.5); color: var(--usdt); border-radius: 999px; font-size: 14px; margin-bottom: 18px; }
.hero h1 { font-size: 52px; font-weight: 900; margin-bottom: 16px; }
.grad { background: linear-gradient(90deg, var(--usdt), var(--blue)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.lead { color: var(--muted); font-size: 17px; max-width: 820px; margin: 0 auto 28px; }
.hero-actions { display: flex; gap: 16px; justify-content: center; flex-wrap: wrap; }

/* Buttons */
.btn { display: inline-block; padding: 14px 34px; border-radius: 999px; font-size: 16px; font-weight: 700; transition: transform 0.25s, box-shadow 0.25s; }
.btn-primary { background: linear-gradient(90deg, var(--usdt), var(--blue)); color: var(--white); box-shadow: 0 8px 24px rgba(38,161,123,0.35); }
.btn-cta { background: linear-gradient(90deg, var(--gold), var(--btc)); color: var(--bg); box-shadow: 0 8px 24px rgba(212,164,55,0.35); }
.btn-outline { border: 1px solid var(--usdt); color: var(--usdt); }
.btn:hover { transform: translateY(-3px); }
.btn-pulse { animation: pulse 2.4s infinite; }
@keyframes pulse { 0%,100% { box-shadow: 0 0 0 0 rgba(38,161,123,0.45); } 50% { box-shadow: 0 0 0 16px rgba(38,161,123,0); } }

/* Sections */
section { padding: 72px 0; }
.section-title { font-size: 34px; font-weight: 800; text-align: center; margin-bottom: 10px; }
.section-sub { color: var(--muted); text-align: center; margin-bottom: 40px; }
.grid { display: grid; gap: 20px; }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }
.card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 26px; transition: transform 0.3s, box-shadow 0.3s; }
.card:hover { transform: translateY(-6px); box-shadow: var(--shadow); }
.card .icon { font-size: 38px; margin-bottom: 12px; }
.card h3 { font-size: 19px; margin-bottom: 10px; color: var(--white); }
.card p { color: var(--muted); font-size: 14.5px; }

/* Stats */
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; }
.stat { text-align: center; padding: 30px 20px; }
.stat .num { font-size: 40px; font-weight: 900; color: var(--usdt); }
.stat .label { color: var(--muted); margin-top: 8px; }

/* Coin rows */
.coin-row { display: flex; justify-content: space-between; padding: 14px 20px; background: var(--card); border: 1px solid var(--line); border-radius: 10px; margin-bottom: 10px; }
.pair { font-weight: 700; }
.price { color: var(--muted); }
.up { color: var(--usdt); font-weight: 700; }
.down { color: var(--btc); font-weight: 700; }

/* Ticker */
.ticker { overflow: hidden; background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 12px 0; }
.ticker-track { display: flex; gap: 40px; white-space: nowrap; animation: ticker 30s linear infinite; }
.ticker-track span { color: var(--muted); }
@keyframes ticker { 0% { transform: translateX(0); } 100% { transform: translateX(-50%); } }

/* Steps */
.step-list { max-width: 860px; margin: 0 auto; }
.step-item { display: flex; gap: 20px; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 22px; margin-bottom: 16px; }
.step-num { min-width: 44px; height: 44px; border-radius: 50%; display: flex; align-items: center; justify-content: center; background: linear-gradient(135deg, var(--usdt), var(--blue)); font-weight: 800; }
.step-item h3 { margin-bottom: 6px; }
.step-item p { color: var(--muted); font-size: 14.5px; }

/* FAQ */
.faq-item { background: var(--card); border: 1px solid var(--line); border-radius: 10px; margin-bottom: 12px; overflow: hidden; }
.faq-item summary { cursor: pointer; padding: 16px 22px; font-weight: 700; color: var(--white); }
.faq-item summary::-webkit-details-marker { display: none; }
.faq-answer { padding: 0 22px 16px; color: var(--muted); font-size: 14.5px; }

/* Contact form */
.contact-form { max-width: 720px; margin: 0 auto; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 34px; }
.contact-form label { display: block; margin: 14px 0 6px; color: var(--muted); }
.contact-form input, .contact-form select, .contact-form textarea { width: 100%; padding: 12px 14px; border-radius: 10px; border: 1px solid var(--line); background: var(--bg2); color: var(--text); font-size: 15px; }
.contact-form .btn { margin-top: 18px; border: 0; cursor: pointer; }

/* Hot words */
.hot-words { display: flex; flex-wrap: wrap; gap: 12px; justify-content: center; }
.tag { padding: 8px 18px; border: 1px solid rgba(38,161,123,0.4); color: var(--usdt); border-radius: 999px; font-size: 14px; }

/* Shield */
.shield { display: inline-block; font-size: 44px; animation: shield 2.2s ease-in-out infinite; }
@keyframes shield { 0%,100% { transform: scale(1); filter: drop-shadow(0 0 2px rgba(38,161,123,0.6)); } 50% { transform: scale(1.08); filter: drop-shadow(0 0 14px rgba(38,161,123,0.9)); } }

/* Web3 nodes */
.web3-nodes { position: relative; min-height: 120px; }
.node { position: absolute; width: 12px; height: 12px; border-radius: 50%; background: var(--usdt); animation: node 3s ease-in-out infinite; }
@keyframes node { 0%,100% { opacity: 0.4; transform: scale(0.8); } 50% { opacity: 1; transform: scale(1.4); } }

/* Reveal / fade */
.reveal { opacity: 0; transform: translateY(24px); transition: opacity 0.6s, transform 0.6s; }
.reveal.visible { opacity: 1; transform: translateY(0); }
.fade-in { animation: fadeIn 0.8s ease both; }
@keyframes fadeIn { from { opacity: 0; transform: translateY(18px); } to { opacity: 1; transform: translateY(0); } }

/* Footer */
.site-footer { border-top: 1px solid var(--line); padding: 30px 0; text-align: center; background: var(--bg2); }
.footer-links { display: flex; gap: 20px; justify-content: center; flex-wrap: wrap; margin-bottom: 14px; }
.footer-links a { color: var(--muted); font-size: 14px; }
.footer-links a:hover { color: var(--usdt); }
.site-footer p { color: var(--muted); font-size: 13.5px; }

/* Responsive */
@media (max-width: 992px) {
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .hero h1 { font-size: 40px; }
}
@media (max-width: 768px) {
  .nav-links { display: none; position: absolute; top: 68px; left: 0; right: 0; flex-direction: column; background: var(--bg2); padding: 20px; gap: 16px; border-bottom: 1px solid var(--line); }
  .nav-links.open { display: flex; }
  .nav-toggle { display: block; }
  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }
  .stats { grid-template-columns: repeat(2, 1fr); }
  .hero { padding: 70px 0 50px; }
  .hero h1 { font-size: 32px; }
  .section-title { font-size: 26px; }
}