:root {
  --bg: #f6f5f2;
  --bg-raised: #ffffff;
  --bg-sunken: #eceae4;
  --ink: #16181d;
  --ink-2: #4a4f59;
  --ink-3: #7b808a;
  --line: #e2dfd7;
  --accent: #4f46e5;
  --accent-ink: #ffffff;
  --accent-soft: #e9e8fd;
  --warm: #e8590c;
  --shadow: 0 1px 2px rgb(22 24 29 / 0.06), 0 12px 32px -12px rgb(22 24 29 / 0.18);
  --radius: 20px;
  --max: 1120px;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1013;
    --bg-raised: #181a1f;
    --bg-sunken: #1f2229;
    --ink: #f2f2f4;
    --ink-2: #b8bcc6;
    --ink-3: #8a8f99;
    --line: #2a2d35;
    --accent: #8b85ff;
    --accent-ink: #0f1013;
    --accent-soft: #24234a;
    --warm: #ff8a4c;
    --shadow: 0 1px 2px rgb(0 0 0 / 0.4), 0 16px 40px -16px rgb(0 0 0 / 0.7);
    color-scheme: dark;
  }
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 17px/1.6 -apple-system, BlinkMacSystemFont, "SF Pro Text", "PingFang SC", "Hiragino Sans GB", "Noto Sans SC", "Segoe UI", Roboto, sans-serif;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; }

img { display: block; max-width: 100%; }

/* One language at a time; JS sets html[lang]. */
html[lang^="zh"] [data-l="en"],
html:not([lang^="zh"]) [data-l="zh"] { display: none !important; }

.wrap { max-width: var(--max); margin: 0 auto; padding: 0 24px; }

/* Header */
.top {
  position: sticky; top: 0; z-index: 10;
  backdrop-filter: saturate(1.4) blur(16px);
  -webkit-backdrop-filter: saturate(1.4) blur(16px);
  background: color-mix(in srgb, var(--bg) 78%, transparent);
  border-bottom: 1px solid color-mix(in srgb, var(--line) 70%, transparent);
}
.top .wrap { display: flex; align-items: center; gap: 16px; height: 64px; }
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; font-weight: 700; font-size: 18px; letter-spacing: -0.01em; }
.brand img { width: 32px; height: 32px; border-radius: 8px; }
.top nav { margin-left: auto; display: flex; align-items: center; gap: 4px; }
.top nav a {
  text-decoration: none; color: var(--ink-2); font-size: 15px;
  padding: 10px 12px; border-radius: 10px; min-height: 44px; display: inline-flex; align-items: center;
}
.top nav a:hover { color: var(--ink); background: var(--bg-sunken); }
.lang {
  border: 1px solid var(--line); background: var(--bg-raised); color: var(--ink-2);
  font: inherit; font-size: 14px; border-radius: 999px; padding: 0 14px; min-height: 36px; cursor: pointer;
}
.lang:hover { color: var(--ink); }

/* Buttons */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 10px;
  min-height: 52px; padding: 0 24px; border-radius: 999px;
  font-weight: 600; font-size: 17px; text-decoration: none; white-space: nowrap;
  transition: transform .15s ease, background-color .15s ease;
}
.btn:active { transform: scale(0.98); }
.btn-primary { background: var(--accent); color: var(--accent-ink); box-shadow: 0 8px 24px -10px var(--accent); }
.btn-primary:hover { background: color-mix(in srgb, var(--accent) 88%, var(--ink)); }
.btn-ghost { background: var(--bg-raised); color: var(--ink); border: 1px solid var(--line); }
.btn-ghost:hover { background: var(--bg-sunken); }
.btn svg { width: 20px; height: 20px; flex: none; }

/* Hero */
.hero { padding: 72px 0 40px; overflow: hidden; }
.hero .wrap { display: grid; grid-template-columns: 1.05fr 0.95fr; gap: 48px; align-items: center; }
.eyebrow {
  display: inline-flex; align-items: center; gap: 8px;
  font-size: 14px; font-weight: 600; color: var(--accent);
  background: var(--accent-soft); padding: 6px 12px; border-radius: 999px;
}
.hero h1 {
  font-size: clamp(40px, 6vw, 68px); line-height: 1.04; letter-spacing: -0.035em;
  margin: 20px 0 20px; font-weight: 800;
}
.hero h1 em { font-style: normal; color: var(--warm); }
.lead { font-size: clamp(18px, 2vw, 20px); color: var(--ink-2); margin: 0 0 32px; max-width: 34em; }
.cta { display: flex; flex-wrap: wrap; gap: 12px; }
.fine { margin-top: 16px; font-size: 14px; color: var(--ink-3); }

.stage { position: relative; display: flex; justify-content: center; min-height: 560px; }
.stage::before {
  content: ""; position: absolute; inset: 8% -10% 0; z-index: 0;
  background:
    radial-gradient(40% 50% at 30% 40%, color-mix(in srgb, var(--accent) 28%, transparent), transparent 70%),
    radial-gradient(40% 45% at 75% 65%, color-mix(in srgb, var(--warm) 22%, transparent), transparent 70%);
  filter: blur(8px);
}
.phone {
  position: relative; z-index: 1;
  width: 280px; aspect-ratio: 1206 / 2622;
  border-radius: 46px; padding: 10px;
  background: #0d0e11;
  box-shadow: var(--shadow), inset 0 0 0 2px #2a2c31;
}
.phone img { width: 100%; height: 100%; object-fit: cover; border-radius: 37px; background: var(--bg-sunken); }
.stage .phone.back { position: absolute; z-index: 0; width: 240px; transform: translate(-46%, 40px) rotate(-6deg); opacity: 0.96; }
.stage .phone.front { transform: translateX(22%); }

/* Sections */
section { padding: 72px 0; }
.sec-head { max-width: 40em; margin-bottom: 40px; }
.sec-head h2 { font-size: clamp(30px, 4vw, 42px); line-height: 1.12; letter-spacing: -0.025em; margin: 0 0 12px; font-weight: 800; }
.sec-head p { color: var(--ink-2); margin: 0; font-size: 18px; }

.grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.card {
  background: var(--bg-raised); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 24px; box-shadow: 0 1px 0 rgb(0 0 0 / 0.02);
}
.card .ic {
  width: 44px; height: 44px; border-radius: 12px; display: grid; place-items: center;
  background: var(--accent-soft); color: var(--accent); margin-bottom: 16px;
}
.card .ic svg { width: 22px; height: 22px; }
.card h3 { margin: 0 0 8px; font-size: 19px; letter-spacing: -0.01em; }
.card p { margin: 0; color: var(--ink-2); font-size: 16px; }
.card.wide { grid-column: 1 / -1; display: grid; grid-template-columns: 1.1fr 0.9fr; gap: 40px; align-items: center; padding: 32px; }
.card.wide p { max-width: 36em; }

/* Assistant mock */
.chat { display: flex; flex-direction: column; gap: 10px; font-size: 15px; }
.bubble { max-width: 88%; padding: 10px 14px; border-radius: 18px; line-height: 1.45; }
.bubble.me { align-self: flex-end; background: var(--accent); color: var(--accent-ink); border-bottom-right-radius: 6px; }
.bubble.bot { align-self: flex-start; background: var(--bg-sunken); border-bottom-left-radius: 6px; }
.tool {
  align-self: flex-start; font: 13px/1.4 ui-monospace, "SF Mono", Menlo, monospace; color: var(--ink-3);
  border: 1px dashed var(--line); border-radius: 10px; padding: 6px 10px;
}
.chips { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 16px; }
.chip { font-size: 13px; font-weight: 600; padding: 5px 10px; border-radius: 999px; background: var(--bg-sunken); color: var(--ink-2); }

/* Join */
.join {
  background: var(--ink); color: var(--bg); border-radius: 32px; padding: 56px;
  display: grid; grid-template-columns: 1.1fr 0.9fr; gap: 40px; align-items: center;
}
.join h2 { color: var(--bg); }
.join .sec-head p { color: color-mix(in srgb, var(--bg) 72%, transparent); }
.join .btn-primary { background: var(--bg); color: var(--ink); box-shadow: none; }
.join .btn-primary:hover { background: color-mix(in srgb, var(--bg) 88%, var(--ink)); }
.steps { list-style: none; margin: 0; padding: 0; display: grid; gap: 16px; counter-reset: s; }
.steps li { display: grid; grid-template-columns: 36px 1fr; gap: 14px; align-items: start; }
.steps li::before {
  counter-increment: s; content: counter(s);
  width: 36px; height: 36px; border-radius: 50%; display: grid; place-items: center; font-weight: 700;
  background: color-mix(in srgb, var(--bg) 14%, transparent); color: var(--bg);
}
.steps b { display: block; }
.steps span { color: color-mix(in srgb, var(--bg) 70%, transparent); font-size: 15px; }
.steps a { color: var(--bg); }

.specs { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.spec { border-top: 1px solid var(--line); padding-top: 14px; }
.spec b { display: block; font-size: 15px; }
.spec span { color: var(--ink-3); font-size: 15px; }

footer { padding: 40px 0 56px; color: var(--ink-3); font-size: 14px; border-top: 1px solid var(--line); }
footer .wrap { display: flex; flex-wrap: wrap; gap: 12px 24px; align-items: center; }
footer a { color: var(--ink-2); text-decoration: none; min-height: 44px; display: inline-flex; align-items: center; }
footer a:hover { color: var(--ink); }
footer .grow { flex: 1; }

/* Prose pages */
.prose { max-width: 720px; padding: 56px 24px 80px; margin: 0 auto; }
.prose h1 { font-size: clamp(32px, 5vw, 44px); letter-spacing: -0.03em; line-height: 1.1; margin: 0 0 8px; }
.prose h2 { font-size: 22px; margin: 40px 0 8px; letter-spacing: -0.01em; }
.prose p, .prose li { color: var(--ink-2); }
.prose .meta { color: var(--ink-3); font-size: 15px; }

@media (max-width: 900px) {
  .hero { padding-top: 40px; }
  .hero .wrap { grid-template-columns: 1fr; gap: 24px; }
  .stage { min-height: 520px; }
  .grid { grid-template-columns: 1fr 1fr; }
  .card.wide { grid-template-columns: 1fr; padding: 24px; }
  .join { grid-template-columns: 1fr; padding: 36px 28px; border-radius: 24px; }
  .specs { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 600px) {
  .wrap { padding: 0 16px; }
  .top nav a.hide-sm { display: none; }
  .grid { grid-template-columns: 1fr; }
  .stage { min-height: 470px; }
  .phone { width: 230px; }
  .stage .phone.back { width: 196px; transform: translate(-36%, 32px) rotate(-6deg); }
  .stage .phone.front { transform: translateX(16%); }
  .cta .btn { width: 100%; }
  section { padding: 56px 0; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .btn { transition: none; }
}