/* ========================================================
   Bitcoin Intro — fintech / dark / gold
   ======================================================== */

:root {
  --bg: #07080b;
  --bg-2: #0b0d12;
  --bg-3: #11141b;
  --line: rgba(255, 196, 0, 0.08);
  --line-strong: rgba(255, 196, 0, 0.22);
  --gold: #f7931a;       /* Bitcoin orange-gold */
  --gold-2: #ffd166;
  --gold-soft: rgba(247, 147, 26, 0.14);
  --text: #e7e9ee;
  --text-dim: #9aa3b2;
  --text-mute: #6b7280;
  --up: #2ecc71;
  --down: #ff4d4f;
  --grid: rgba(255, 255, 255, 0.04);
  --shadow: 0 30px 60px -30px rgba(0, 0, 0, 0.8);
  --font-zh: "PingFang SC", "Microsoft YaHei", "Noto Sans SC", sans-serif;
  --font-en: "Inter", "Helvetica Neue", Arial, sans-serif;
  --font-mono: "JetBrains Mono", "SF Mono", "Menlo", "Consolas", monospace;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-en), var(--font-zh);
  font-size: 16px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body { overflow-x: hidden; }

a { color: inherit; text-decoration: none; }
a:hover { color: var(--gold); }

::selection { background: var(--gold); color: #000; }

/* ---------- Background Grid ---------- */
.grid-bg {
  position: fixed; inset: 0;
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 56px 56px;
  pointer-events: none;
  z-index: 0;
  mask-image: radial-gradient(ellipse at top, #000 0%, transparent 75%);
}

body::before {
  content: "";
  position: fixed; inset: -10% -10% 60% -10%;
  background:
    radial-gradient(800px 400px at 20% 0%, rgba(247,147,26,0.18), transparent 60%),
    radial-gradient(700px 400px at 90% 10%, rgba(255,209,102,0.10), transparent 65%);
  z-index: 0; pointer-events: none;
}

/* ---------- Nav ---------- */
.nav {
  position: sticky; top: 0; z-index: 50;
  display: flex; align-items: center; justify-content: space-between;
  padding: 18px 48px;
  backdrop-filter: blur(14px);
  background: rgba(7, 8, 11, 0.65);
  border-bottom: 1px solid var(--line);
}

.brand {
  display: inline-flex; align-items: center; gap: 12px;
  font-family: var(--font-mono);
  letter-spacing: 1.2px;
}

.brand-mark {
  display: inline-flex; align-items: center; justify-content: center;
  width: 34px; height: 34px;
  background: linear-gradient(135deg, var(--gold) 0%, var(--gold-2) 100%);
  color: #1a1300;
  border-radius: 8px;
  font-weight: 700; font-size: 20px;
  box-shadow: 0 6px 22px -8px var(--gold);
}

.brand-text {
  font-weight: 700; font-size: 14px;
}

.brand-sub {
  color: var(--gold);
  margin-left: 4px;
  font-weight: 400;
}

.brand.small .brand-mark { width: 28px; height: 28px; font-size: 16px; }

.nav-links {
  display: flex; gap: 28px;
  font-size: 14px;
  color: var(--text-dim);
}
.nav-links a {
  position: relative;
  padding: 6px 2px;
}
.nav-links a::after {
  content: ""; position: absolute; left: 0; right: 0; bottom: -2px;
  height: 2px;
  background: linear-gradient(90deg, var(--gold), transparent);
  transform: scaleX(0); transform-origin: left;
  transition: transform .25s ease;
}
.nav-links a:hover { color: var(--text); }
.nav-links a:hover::after { transform: scaleX(1); }

/* ---------- Hero ---------- */
main { position: relative; z-index: 1; }

.hero {
  padding: 80px 48px 60px;
  max-width: 1280px;
  margin: 0 auto;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.1fr 1fr;
  gap: 56px;
  align-items: stretch;
}

.eyebrow {
  display: inline-flex; align-items: center; gap: 10px;
  padding: 6px 12px;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 1.5px;
  color: var(--text-dim);
  background: rgba(247,147,26,0.04);
  text-transform: uppercase;
}

.dot {
  width: 8px; height: 8px; border-radius: 50%;
  background: var(--up);
  box-shadow: 0 0 12px var(--up);
  animation: pulse 2s ease-in-out infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.5; transform: scale(0.85); }
}

.hero h1 {
  margin: 22px 0 18px;
  font-size: clamp(48px, 6vw, 84px);
  line-height: 1.02;
  letter-spacing: -2px;
  font-weight: 800;
}

.hero-accent {
  display: block;
  background: linear-gradient(120deg, var(--gold) 0%, var(--gold-2) 50%, #fff 110%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

.lede {
  font-size: 18px;
  color: var(--text-dim);
  max-width: 540px;
  margin: 0 0 32px;
}

.cta-row { display: flex; gap: 14px; flex-wrap: wrap; }

.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 14px 22px;
  border-radius: 10px;
  font-weight: 600;
  font-size: 14px;
  letter-spacing: 0.4px;
  cursor: pointer;
  transition: transform .15s ease, box-shadow .25s ease;
}

.btn.primary {
  background: linear-gradient(120deg, var(--gold), var(--gold-2));
  color: #1a1300;
  box-shadow: 0 12px 30px -10px var(--gold);
}
.btn.primary:hover { transform: translateY(-2px); box-shadow: 0 18px 36px -12px var(--gold); }

.btn.ghost {
  background: transparent;
  color: var(--text);
  border: 1px solid var(--line-strong);
}
.btn.ghost:hover { border-color: var(--gold); color: var(--gold); }

/* Ticker / card */
.hero-card {
  background: linear-gradient(160deg, var(--bg-3) 0%, var(--bg-2) 100%);
  border: 1px solid var(--line);
  border-radius: 18px;
  padding: 22px 24px 18px;
  box-shadow: var(--shadow);
  display: flex; flex-direction: column; gap: 14px;
  position: relative;
  overflow: hidden;
}
.hero-card::before {
  content: ""; position: absolute; inset: -2px;
  background: linear-gradient(140deg, transparent 30%, rgba(247,147,26,0.25), transparent 70%);
  z-index: -1; filter: blur(20px); opacity: .35;
}

.card-head {
  display: flex; justify-content: space-between; align-items: center;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--text-dim);
}

.badge {
  font-size: 10px;
  padding: 3px 8px;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  color: var(--gold);
  background: var(--gold-soft);
}

.ticker-row {
  display: flex; align-items: baseline; gap: 14px;
}
.ticker-price {
  font-family: var(--font-mono);
  font-size: 38px;
  font-weight: 700;
  color: #fff;
  letter-spacing: -1px;
}
.ticker-change {
  font-family: var(--font-mono);
  font-size: 14px;
  padding: 4px 10px;
  border-radius: 6px;
}
.ticker-change.up { color: var(--up); background: rgba(46,204,113,0.10); }
.ticker-change.down { color: var(--down); background: rgba(255,77,79,0.10); }

.ticker-meta {
  display: grid; grid-template-columns: repeat(3, 1fr);
  gap: 12px;
  border-top: 1px dashed var(--line);
  padding-top: 12px;
  font-family: var(--font-mono);
}
.ticker-meta div { display: flex; flex-direction: column; gap: 2px; font-size: 12px; }
.ticker-meta label { color: var(--text-mute); font-size: 10px; letter-spacing: .5px; text-transform: uppercase; }
.ticker-meta span { color: var(--text); }

#priceChart {
  width: 100%;
  height: 180px;
  display: block;
}

.card-foot {
  color: var(--text-mute);
  font-size: 11px;
  text-align: center;
}

/* Stats strip */
.stat-strip {
  margin-top: 60px;
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 0;
  border: 1px solid var(--line);
  border-radius: 14px;
  overflow: hidden;
  background: linear-gradient(180deg, rgba(255,255,255,0.02), transparent);
}
.stat {
  padding: 22px 24px;
  border-right: 1px solid var(--line);
}
.stat:last-child { border-right: none; }
.stat-num {
  font-family: var(--font-mono);
  font-size: 24px;
  font-weight: 700;
  color: #fff;
  letter-spacing: -.5px;
}
.stat-label {
  margin-top: 4px;
  color: var(--text-mute);
  font-size: 12px;
  letter-spacing: .4px;
}

/* ---------- Section base ---------- */
.section {
  padding: 100px 48px;
  max-width: 1280px;
  margin: 0 auto;
  position: relative;
}
.section.alt::before {
  content: "";
  position: absolute;
  inset: 0 -50vw;
  background: linear-gradient(180deg, transparent, rgba(247,147,26,0.04) 30%, transparent 100%);
  z-index: -1;
}

.section-head { max-width: 760px; margin-bottom: 50px; }
.section-tag {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 2px;
  color: var(--gold);
  padding: 4px 10px;
  border: 1px solid var(--line-strong);
  border-radius: 4px;
  background: var(--gold-soft);
  text-transform: uppercase;
}
.section-head h2 {
  margin: 18px 0 14px;
  font-size: clamp(34px, 4vw, 52px);
  letter-spacing: -1px;
  line-height: 1.1;
  font-weight: 800;
}
.zh-en {
  display: inline-block;
  margin-left: 12px;
  font-family: var(--font-mono);
  font-size: 14px;
  color: var(--text-mute);
  font-weight: 400;
  letter-spacing: 1px;
  vertical-align: middle;
}
.section-lede { color: var(--text-dim); font-size: 17px; max-width: 640px; }

/* ---------- Info cards ---------- */
.card-grid {
  display: grid; gap: 22px;
}
.card-grid.three { grid-template-columns: repeat(3, 1fr); }
.card-grid.two { grid-template-columns: repeat(2, 1fr); }

.info-card {
  background: linear-gradient(180deg, rgba(255,255,255,0.025), transparent);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 28px 26px;
  position: relative;
  transition: border-color .3s ease, transform .25s ease;
}
.info-card:hover {
  border-color: var(--line-strong);
  transform: translateY(-3px);
}
.info-card.dark {
  background: linear-gradient(160deg, var(--bg-3), var(--bg-2));
}
.ic-num {
  font-family: var(--font-mono);
  color: var(--gold);
  font-size: 12px;
  margin-bottom: 14px;
  letter-spacing: 2px;
}
.info-card h3 {
  margin: 0 0 10px;
  font-size: 19px;
  letter-spacing: -.2px;
}
.info-card p {
  color: var(--text-dim);
  margin: 0;
  font-size: 15px;
}

/* Callout */
.callout {
  margin-top: 40px;
  display: flex; gap: 18px; align-items: flex-start;
  background: linear-gradient(120deg, rgba(247,147,26,0.10), rgba(255,209,102,0.04));
  border: 1px solid var(--line-strong);
  border-radius: 14px;
  padding: 22px 26px;
}
.callout-mark {
  flex-shrink: 0;
  width: 30px; height: 30px;
  border-radius: 50%;
  background: var(--gold);
  color: #1a1300;
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-mono);
  font-weight: 700;
  font-style: italic;
}
.callout strong { color: var(--gold); }

/* ---------- Timeline ---------- */
.timeline {
  list-style: none;
  padding: 0;
  margin: 0;
  position: relative;
}
.timeline::before {
  content: "";
  position: absolute;
  left: 110px;
  top: 6px;
  bottom: 6px;
  width: 1px;
  background: linear-gradient(180deg, var(--gold), transparent);
}
.timeline li {
  position: relative;
  display: grid;
  grid-template-columns: 110px 1fr;
  gap: 30px;
  padding: 18px 0;
}
.timeline li::before {
  content: "";
  position: absolute;
  left: 105px; top: 26px;
  width: 11px; height: 11px;
  background: var(--gold);
  border-radius: 50%;
  box-shadow: 0 0 0 4px rgba(247,147,26,0.18);
}
.tl-date {
  font-family: var(--font-mono);
  color: var(--gold);
  font-weight: 600;
  font-size: 14px;
}
.tl-body h3 {
  margin: 0 0 6px;
  font-size: 19px;
}
.tl-body p { margin: 0; color: var(--text-dim); }
.tl-body code {
  font-family: var(--font-mono);
  font-size: 12px;
  background: rgba(255,255,255,0.05);
  padding: 2px 6px;
  border-radius: 4px;
  color: var(--gold-2);
}

/* ---------- Mech grid ---------- */
.mech-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}
.mech {
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 26px 22px;
  background: linear-gradient(180deg, rgba(255,255,255,0.02), transparent);
  transition: all .25s ease;
}
.mech:hover {
  border-color: var(--gold);
  box-shadow: 0 12px 30px -16px rgba(247,147,26,0.5);
}
.mech-icon {
  font-size: 28px;
  margin-bottom: 12px;
  filter: drop-shadow(0 4px 10px rgba(247,147,26,0.4));
}
.mech h3 { margin: 0 0 8px; font-size: 17px; }
.mech p { margin: 0; color: var(--text-dim); font-size: 14px; }
.mech em { font-style: normal; color: var(--gold); font-weight: 600; }

/* Flow */
.flow {
  margin-top: 50px;
  border: 1px dashed var(--line-strong);
  border-radius: 14px;
  padding: 30px 24px;
  background: rgba(247,147,26,0.03);
}
.flow-title {
  font-family: var(--font-mono);
  color: var(--gold);
  font-size: 13px;
  letter-spacing: 2px;
  text-transform: uppercase;
  margin: 0 0 22px;
  text-align: center;
}
.flow-steps {
  display: flex; align-items: center; justify-content: center; flex-wrap: wrap; gap: 10px;
}
.step {
  display: flex; align-items: center; gap: 10px;
  padding: 12px 14px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--bg-3);
  min-width: 140px;
}
.step span {
  display: inline-flex; align-items: center; justify-content: center;
  width: 26px; height: 26px;
  background: var(--gold);
  color: #1a1300;
  font-family: var(--font-mono);
  font-weight: 700;
  border-radius: 50%;
  font-size: 12px;
}
.step p { margin: 0; font-size: 13px; color: var(--text); }
.arrow { color: var(--gold); font-family: var(--font-mono); font-size: 18px; }

/* ---------- Metric row ---------- */
.metric-row {
  margin-top: 36px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0;
  border: 1px solid var(--line);
  border-radius: 14px;
  overflow: hidden;
  background: linear-gradient(180deg, rgba(255,255,255,0.02), transparent);
}
.metric {
  padding: 22px 24px;
  border-right: 1px solid var(--line);
}
.metric:last-child { border-right: none; }
.metric label {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 1.2px;
  text-transform: uppercase;
  color: var(--text-mute);
}
.metric strong {
  display: block;
  margin: 4px 0 2px;
  font-family: var(--font-mono);
  font-size: 22px;
  color: var(--gold);
}
.metric span {
  display: block;
  font-size: 12px;
  color: var(--text-dim);
}

/* ---------- Use cases ---------- */
.use-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
}
.use {
  padding: 22px 22px 26px;
  border-left: 2px solid var(--gold);
  background: linear-gradient(90deg, rgba(247,147,26,0.05), transparent 80%);
  border-radius: 0 10px 10px 0;
}
.use h3 { margin: 0 0 8px; font-size: 17px; }
.use p { margin: 0; color: var(--text-dim); font-size: 14px; }

/* ---------- Risk ---------- */
.risk-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
}
.risk {
  padding: 24px 22px;
  border: 1px solid rgba(255,77,79,0.18);
  border-radius: 14px;
  background: linear-gradient(180deg, rgba(255,77,79,0.05), transparent 70%);
  position: relative;
}
.risk-no {
  display: inline-flex; align-items: center; justify-content: center;
  width: 26px; height: 26px;
  background: var(--down);
  color: #fff;
  border-radius: 6px;
  font-weight: 700;
  font-family: var(--font-mono);
  margin-bottom: 10px;
}
.risk h3 { margin: 0 0 6px; font-size: 17px; }
.risk p { margin: 0; color: var(--text-dim); font-size: 14px; }

.warn {
  margin-top: 34px;
  padding: 18px 22px;
  border: 1px solid var(--line-strong);
  border-radius: 12px;
  background: rgba(247,147,26,0.07);
  color: var(--text-dim);
  font-size: 14px;
}
.warn strong { color: var(--gold); }

/* ---------- Reference ---------- */
.ref {
  list-style: none;
  padding: 0; margin: 0;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 14px;
}
.ref li {
  display: flex; align-items: center; gap: 14px;
  padding: 14px 18px;
  border: 1px solid var(--line);
  border-radius: 10px;
  transition: border-color .2s ease;
}
.ref li:hover { border-color: var(--gold); }
.ref-tag {
  font-family: var(--font-mono);
  background: var(--gold-soft);
  color: var(--gold);
  font-size: 11px;
  padding: 3px 8px;
  border-radius: 4px;
  letter-spacing: 1px;
}

/* ---------- Footer ---------- */
.footer {
  margin-top: 60px;
  padding: 60px 48px 24px;
  border-top: 1px solid var(--line);
  background: linear-gradient(180deg, transparent, rgba(247,147,26,0.04));
}
.foot-cols {
  max-width: 1280px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr 1.4fr;
  gap: 40px;
}
.foot-cols h4 {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 2px;
  color: var(--gold);
  text-transform: uppercase;
  margin: 0 0 14px;
}
.foot-cols a {
  display: block;
  color: var(--text-dim);
  font-size: 14px;
  padding: 4px 0;
}
.foot-desc { color: var(--text-dim); font-size: 14px; margin: 16px 0 0; }
.foot-tiny { color: var(--text-mute); font-size: 12px; margin: 0; line-height: 1.6; }

.copy {
  max-width: 1280px;
  margin: 40px auto 0;
  padding-top: 22px;
  border-top: 1px solid var(--line);
  font-family: var(--font-mono);
  color: var(--text-mute);
  font-size: 11px;
  text-align: center;
  letter-spacing: 1px;
}

/* ---------- Reveal ---------- */
.section { opacity: 0; transform: translateY(20px); transition: opacity .6s ease, transform .6s ease; }
.section.in-view { opacity: 1; transform: translateY(0); }
.hero { opacity: 1; }

/* ---------- Responsive ---------- */
@media (max-width: 1024px) {
  .hero-grid { grid-template-columns: 1fr; }
  .stat-strip { grid-template-columns: repeat(2, 1fr); }
  .stat { border-right: none; border-bottom: 1px solid var(--line); }
  .card-grid.three, .mech-grid, .use-grid, .risk-grid { grid-template-columns: repeat(2, 1fr); }
  .ref { grid-template-columns: 1fr; }
  .foot-cols { grid-template-columns: repeat(2, 1fr); }
  .metric-row { grid-template-columns: repeat(2, 1fr); }
  .metric { border-bottom: 1px solid var(--line); }
}

@media (max-width: 640px) {
  .nav { padding: 14px 18px; }
  .nav-links { display: none; }
  .hero { padding: 48px 18px 24px; }
  .section { padding: 64px 18px; }
  .footer { padding: 40px 18px 24px; }
  .hero h1 { font-size: 44px; }
  .stat-strip { grid-template-columns: 1fr; }
  .stat { border-right: none; border-bottom: 1px solid var(--line); }
  .card-grid.three, .card-grid.two, .mech-grid, .use-grid, .risk-grid { grid-template-columns: 1fr; }
  .foot-cols { grid-template-columns: 1fr; }
  .timeline::before { left: 6px; }
  .timeline li { grid-template-columns: 1fr; gap: 6px; padding-left: 26px; }
  .timeline li::before { left: 1px; top: 26px; }
  .flow-steps { flex-direction: column; }
  .arrow { transform: rotate(90deg); }
  .metric-row { grid-template-columns: 1fr; }
  .metric { border-right: none; border-bottom: 1px solid var(--line); }
}