:root {
  --bg: #0c0b0a;
  --bg-2: #161412;
  --line: #2a2622;
  --text: #f3efe9;
  --muted: #a39b91;
  --accent: #e8a33d;      /* warm amber — deliberately not NVIDIA green */
  --accent-ink: #1a1207;
  --radius: 14px;
  --max: 1080px;
  --font: "Inter", "Noto Sans SC", system-ui, -apple-system, "PingFang SC", "Microsoft YaHei", sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); }
img { max-width: 100%; }

/* language switching */
html[data-lang="zh"] [lang="en"],
html[data-lang="en"] [lang="zh"] { display: none !important; }


.nav {
  position: sticky; top: 0; z-index: 10;
  display: flex; align-items: center; gap: 16px;
  max-width: var(--max); margin: 0 auto;
  padding: 14px 16px;
  background: rgba(12, 11, 10, .85);
  backdrop-filter: blur(10px);
}
.brand {
  font-weight: 800; font-size: 22px; letter-spacing: .5px;
  color: var(--text); text-decoration: none;
}
.brand .four { color: var(--accent); }
.nav-links { display: flex; gap: 20px; align-items: center; margin-left: auto; }
.nav-links a:not(.btn) { color: var(--muted); text-decoration: none; font-size: 15px; }
.nav-links a:not(.btn):hover { color: var(--text); }
.lang-toggle {
  background: none; border: 1px solid var(--line); color: var(--text);
  border-radius: 999px; padding: 6px 12px; font: inherit; font-size: 13px; cursor: pointer;
}

.btn {
  display: inline-block;
  background: var(--accent); color: var(--accent-ink);
  border: 1px solid var(--accent);
  padding: 12px 22px; border-radius: 999px;
  font: inherit; font-weight: 600; text-decoration: none; cursor: pointer;
  transition: transform .15s, opacity .15s;
}
.btn:hover { transform: translateY(-1px); }
.btn:disabled { opacity: .6; cursor: wait; transform: none; }
.btn-sm { padding: 7px 16px; font-size: 14px; }
.btn-ghost { background: transparent; color: var(--text); border-color: var(--line); }
.btn-ghost:hover { border-color: var(--accent); }
.btn-block { width: 100%; }

main > section { max-width: var(--max); margin: 0 auto; padding-left: 16px; padding-right: 16px; }

.hero { padding-top: 96px; padding-bottom: 72px; text-align: center; }
.eyebrow { color: var(--accent); font-weight: 600; letter-spacing: 2px; text-transform: uppercase; font-size: 13px; }
.hero h1 {
  font-size: clamp(40px, 8vw, 84px);
  line-height: 1.05; margin: 16px 0 24px; font-weight: 800; letter-spacing: -1.5px;
}
.accent { color: var(--accent); }
.lead { max-width: 680px; margin: 0 auto 32px; color: var(--muted); font-size: 18px; }
.hero-cta { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.counter { margin-top: 28px; color: var(--muted); }
.counter strong { color: var(--text); font-size: 28px; margin-right: 6px; }

.card {
  background: var(--bg-2); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 24px 28px;
}
.h-small { font-size: 14px; text-transform: uppercase; letter-spacing: 2px; color: var(--muted); margin: 0 0 8px; }
.source { font-size: 14px; color: var(--muted); margin-bottom: 0; }

.section { padding-top: 80px; padding-bottom: 16px; }
.section h2 { font-size: clamp(28px, 4vw, 40px); margin: 0 0 28px; letter-spacing: -.5px; }

.grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); gap: 16px; }
.tile { background: var(--bg-2); border: 1px solid var(--line); border-radius: var(--radius); padding: 24px; }
.tile .num { font-size: 32px; font-weight: 800; color: var(--accent); }
.tile h3 { margin: 8px 0; font-size: 18px; }
.tile p { margin: 0; color: var(--muted); font-size: 15px; }

.principles { list-style: none; counter-reset: p; padding: 0; margin: 0; display: grid; gap: 12px; }
.principles li {
  counter-increment: p; position: relative;
  background: var(--bg-2); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 20px 24px 20px 72px; color: var(--muted);
}
.principles li::before {
  content: counter(p, decimal-leading-zero);
  position: absolute; left: 24px; top: 20px;
  color: var(--accent); font-weight: 800;
}
.principles strong { display: block; color: var(--text); margin-bottom: 4px; }

.sign { display: grid; grid-template-columns: 1fr 1.1fr; gap: 40px; align-items: start; }
.sign-copy p { color: var(--muted); }
.muted { font-size: 14px; }
.form {
  background: var(--bg-2); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 28px; display: grid; gap: 14px;
}
.form label { display: grid; gap: 6px; font-size: 14px; color: var(--muted); }
.form input:not([type="checkbox"]), .form select, .form textarea {
  width: 100%; background: var(--bg); color: var(--text);
  border: 1px solid var(--line); border-radius: 10px; padding: 11px 12px; font: inherit; font-size: 15px;
}
.form input:focus, .form select:focus, .form textarea:focus { outline: 2px solid var(--accent); outline-offset: 1px; border-color: transparent; }
.form .row { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
.form .check { display: flex; gap: 10px; align-items: flex-start; }
.form .check input { margin-top: 4px; accent-color: var(--accent); }
.hp { position: absolute; left: -9999px; }
.form-status { margin: 0; min-height: 1.5em; font-size: 14px; }
.form-status.ok { color: var(--accent); }
.form-status.err { color: #ff7a6b; }

.share { text-align: center; }
.tag { font-size: clamp(36px, 6vw, 56px); font-weight: 800; color: var(--accent); margin: 0 0 24px; }
.share-buttons { display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; }

details { border-bottom: 1px solid var(--line); padding: 16px 0; }
summary { cursor: pointer; font-weight: 600; font-size: 17px; }
details p { color: var(--muted); margin: 12px 0 0; }

.footer {
  max-width: var(--max); margin: 96px auto 0; padding: 32px 16px 48px;
  border-top: 1px solid var(--line); color: var(--muted); font-size: 13px;
}
.footer .brand { font-size: 18px; }

/* privacy page */
.doc { max-width: 760px; margin: 0 auto; padding: 48px 16px; }
.doc h1 { font-size: 36px; }
.doc p, .doc li { color: var(--muted); }

@media (max-width: 760px) {
  .nav-links a:not(.btn) { display: none; }
  .sign { grid-template-columns: 1fr; }
  .form .row { grid-template-columns: 1fr; }
  .hero { padding-top: 56px; }
  .principles li { padding-left: 60px; }
  .principles li::before { left: 18px; }
}

.signers { padding-top: 40px; }
.signer-list { list-style: none; padding: 0; margin: 0; display: flex; flex-wrap: wrap; gap: 8px; }
.signer-list li {
  background: var(--bg-2); border: 1px solid var(--line); border-radius: 999px;
  padding: 6px 14px; font-size: 14px; color: var(--muted);
}
.signer-list strong { color: var(--text); font-weight: 600; }