/* VAI OS 官网样式 —— 普通用户向：深色为主、语言朴素 */
:root {
  --bg: #0b0d12;
  --bg-alt: #0f1218;
  --surface: #141821;
  --surface-2: #1a1f2b;
  --line: #232a38;
  --text: #e8ecf4;
  --text-2: #9aa6bd;
  --text-3: #6b7791;
  --brand: #4d6bfe;
  --brand-2: #7c5cff;
  --ok: #3ddc97;
  --warn: #f0b34a;
  --radius: 14px;
  --maxw: 1120px;
  --font: "Inter", "PingFang SC", "Microsoft YaHei", system-ui, -apple-system, "Segoe UI", sans-serif;
  --mono: "JetBrains Mono", "SFMono-Regular", Consolas, "Cascadia Mono", monospace;
}

:root[data-theme="light"] {
  --bg: #ffffff;
  --bg-alt: #f6f8fc;
  --surface: #ffffff;
  --surface-2: #f2f5fb;
  --line: #e3e8f2;
  --text: #10182a;
  --text-2: #4d5a75;
  --text-3: #7c879e;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

strong { font-weight: 650; }
a { color: inherit; text-decoration: none; }

.skip {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--brand);
  color: #fff;
  padding: 10px 16px;
  border-radius: 0 0 10px 0;
  z-index: 100;
}
.skip:focus { left: 0; }

.wrap {
  width: 100%;
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 24px;
}
.wrap.narrow { max-width: 820px; }

/* ---------- 导航 ---------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in srgb, var(--bg) 78%, transparent);
  backdrop-filter: saturate(160%) blur(14px);
  border-bottom: 1px solid transparent;
  transition: border-color 0.25s, background 0.25s;
}
.nav.scrolled {
  border-bottom-color: var(--line);
  background: color-mix(in srgb, var(--bg) 92%, transparent);
}
.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 650;
}
/* 品牌标直接使用官方 logo（PNG），圆角与阴影只做轻微修饰 */
.brand-mark {
  width: 26px;
  height: 26px;
  border-radius: 7px;
  object-fit: cover;
  box-shadow: 0 6px 18px -8px var(--brand);
  flex: none;
  display: block;
}
.brand-name { font-size: 17px; }
.tag {
  font-size: 11px;
  line-height: 18px;
  padding: 0 8px;
  border-radius: 999px;
  border: 1px solid color-mix(in srgb, var(--brand) 45%, transparent);
  color: color-mix(in srgb, var(--brand) 78%, var(--text));
  font-weight: 500;
  white-space: nowrap;
}
.nav-links {
  display: flex;
  align-items: center;
  gap: 26px;
  font-size: 15px;
  color: var(--text-2);
}
.nav-links a:hover { color: var(--text); }
.nav-cta {
  padding: 7px 16px;
  border-radius: 999px;
  background: var(--brand);
  color: #fff !important;
  font-weight: 560;
  box-shadow: 0 8px 22px -12px var(--brand);
}
.nav-cta:hover { filter: brightness(1.08); }
.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: 0;
  cursor: pointer;
  padding: 8px;
}
.nav-toggle span {
  width: 20px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: transform 0.2s, opacity 0.2s;
}
.nav-toggle[aria-expanded="true"] span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }
.mobile-menu {
  display: none;
  flex-direction: column;
  gap: 4px;
  padding: 8px 24px 18px;
  border-bottom: 1px solid var(--line);
  background: var(--bg);
}
.mobile-menu a { padding: 10px 0; color: var(--text-2); border-bottom: 1px solid var(--line); }

/* ---------- 首屏 ---------- */
.hero {
  position: relative;
  overflow: hidden;
  padding: 84px 0 72px;
}
.hero-grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(to right, color-mix(in srgb, var(--text) 6%, transparent) 1px, transparent 1px),
    linear-gradient(to bottom, color-mix(in srgb, var(--text) 6%, transparent) 1px, transparent 1px);
  background-size: 56px 56px;
  mask-image: radial-gradient(ellipse 80% 60% at 50% 0%, #000 30%, transparent 75%);
  -webkit-mask-image: radial-gradient(ellipse 80% 60% at 50% 0%, #000 30%, transparent 75%);
}
.hero-glow {
  position: absolute;
  top: -180px;
  left: 50%;
  width: 900px;
  height: 520px;
  transform: translateX(-50%);
  background: radial-gradient(circle at 50% 50%, color-mix(in srgb, var(--brand) 35%, transparent), transparent 62%);
  filter: blur(30px);
  pointer-events: none;
}
.hero-inner { position: relative; text-align: center; }
.pill {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  color: var(--text-2);
  border: 1px solid var(--line);
  background: color-mix(in srgb, var(--surface) 70%, transparent);
  padding: 5px 14px;
  border-radius: 999px;
  margin: 0 0 22px;
}
.pill .dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--ok);
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--ok) 18%, transparent);
}
.hero h1 {
  margin: 0 0 20px;
  font-size: clamp(34px, 5.4vw, 60px);
  line-height: 1.14;
  letter-spacing: -0.02em;
  font-weight: 700;
}
.grad {
  background: linear-gradient(100deg, var(--brand), var(--brand-2) 55%, #ff7ac6);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.lede {
  max-width: 700px;
  margin: 0 auto 30px;
  color: var(--text-2);
  font-size: clamp(15px, 1.6vw, 17.5px);
}
.lede strong { color: var(--text); }
.hero-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}
.hero-actions.center { margin-top: 26px; }
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 24px;
  border-radius: 10px;
  font-weight: 600;
  font-size: 15px;
  transition: transform 0.15s, box-shadow 0.2s, background 0.2s;
  cursor: pointer;
}
.btn:hover { transform: translateY(-1px); }
.btn.primary {
  background: linear-gradient(135deg, var(--brand), var(--brand-2));
  color: #fff;
  box-shadow: 0 14px 30px -14px var(--brand);
}
.btn.ghost {
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--text);
}
.btn.ghost:hover { border-color: color-mix(in srgb, var(--brand) 50%, var(--line)); }

/* 对话演示 */
.chat-demo {
  max-width: 640px;
  margin: 46px auto 0;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: linear-gradient(180deg, #11151d, #0d1017);
  box-shadow: 0 40px 80px -50px #000, 0 0 0 1px color-mix(in srgb, var(--brand) 12%, transparent);
  overflow: hidden;
  text-align: left;
}
.term-bar {
  display: flex;
  align-items: center;
  gap: 7px;
  padding: 10px 14px;
  border-bottom: 1px solid #1c2230;
  background: #0a0d12;
}
.tl { width: 11px; height: 11px; border-radius: 50%; display: inline-block; }
.tl.r { background: #ff5f57; }
.tl.y { background: #febc2e; }
.tl.g { background: #28c840; }
.term-title { margin-left: 10px; font-size: 12.5px; color: #68738a; }
.chat {
  display: flex;
  flex-direction: column;
  gap: 12px;
  padding: 22px 20px 24px;
}
.bubble {
  max-width: 84%;
  padding: 11px 15px;
  border-radius: 14px;
  font-size: 14.5px;
  line-height: 1.65;
  color: #dfe6f2;
}
.bubble.me {
  align-self: flex-end;
  background: linear-gradient(135deg, #3d56d6, #6a56e0);
  color: #fff;
  border-bottom-right-radius: 5px;
}
.bubble.ai {
  align-self: flex-start;
  background: #1a2030;
  border: 1px solid #263045;
  border-bottom-left-radius: 5px;
}

/* 统计条 */
.stats {
  list-style: none;
  padding: 28px 0 0;
  margin: 44px 0 0;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
  border-top: 1px solid var(--line);
}
.stats li { display: flex; flex-direction: column; gap: 2px; }
.stats b { font-size: clamp(20px, 2.4vw, 26px); font-weight: 700; }
.stats span { font-size: 13px; color: var(--text-3); }

/* ---------- 通用区块 ---------- */
.section { padding: 92px 0; }
.section.alt { background: var(--bg-alt); border-block: 1px solid var(--line); }
.sec-head { max-width: 760px; margin: 0 0 44px; }
.sec-head.center { margin-inline: auto; text-align: center; }
.eyebrow {
  margin: 0 0 10px;
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.1em;
  color: color-mix(in srgb, var(--brand) 78%, var(--text));
}
.sec-head h2 {
  margin: 0 0 12px;
  font-size: clamp(25px, 3.4vw, 36px);
  line-height: 1.25;
  letter-spacing: -0.015em;
}
.sub { margin: 0; color: var(--text-2); font-size: 16px; }

/* ---------- 微信客服 ---------- */
.section.kefu {
  background:
    radial-gradient(ellipse 70% 60% at 50% 0%, color-mix(in srgb, #07c160 10%, transparent), transparent 70%),
    var(--bg);
  border-top: 1px solid var(--line);
}
.kefu-grid {
  display: grid;
  grid-template-columns: 0.85fr 1.15fr;
  gap: 44px;
  align-items: center;
}

/* 手机示意 */
.phone {
  border-radius: 26px;
  border: 1px solid var(--line);
  background: #0e1118;
  padding: 14px 12px 12px;
  box-shadow: 0 40px 70px -50px #000;
}
.phone-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 4px 6px 12px;
  border-bottom: 1px solid #1c2230;
  margin-bottom: 12px;
}
.phone-title { font-size: 13.5px; color: #cfd8e8; font-weight: 600; }
.phone-badge {
  font-size: 11px;
  color: #07c160;
  border: 1px solid color-mix(in srgb, #07c160 45%, transparent);
  background: color-mix(in srgb, #07c160 12%, transparent);
  padding: 2px 8px;
  border-radius: 999px;
  white-space: nowrap;
}
.phone-body { display: flex; flex-direction: column; gap: 10px; }
.msg {
  max-width: 86%;
  padding: 10px 13px;
  border-radius: 12px;
  font-size: 13.5px;
  line-height: 1.6;
}
.msg.them { align-self: flex-start; background: #1a2030; border: 1px solid #263045; color: #dfe6f2; border-bottom-left-radius: 4px; }
.msg.us { align-self: flex-end; background: #07c160; color: #06230f; font-weight: 500; border-bottom-right-radius: 4px; }
.phone-foot {
  margin-top: 14px;
  padding-top: 12px;
  border-top: 1px dashed #263045;
  font-size: 12px;
  color: #7f8ba3;
  text-align: center;
}

.kefu-points { list-style: none; margin: 0; padding: 0; display: grid; gap: 18px; }
.kefu-points li { display: flex; gap: 14px; }
.k-icon {
  flex: none;
  width: 42px;
  height: 42px;
  display: grid;
  place-items: center;
  font-size: 19px;
  border-radius: 12px;
  background: color-mix(in srgb, #07c160 12%, transparent);
  border: 1px solid color-mix(in srgb, #07c160 25%, transparent);
}
.kefu-points h4 { margin: 2px 0 4px; font-size: 16.5px; }
.kefu-points p { margin: 0; font-size: 14.5px; color: var(--text-2); }
.kefu-note {
  margin-top: 22px;
  padding: 12px 16px;
  font-size: 13px;
  color: var(--text-3);
  border-left: 2px solid color-mix(in srgb, #07c160 55%, transparent);
  background: color-mix(in srgb, #07c160 6%, transparent);
  border-radius: 0 8px 8px 0;
}

/* ---------- 能力卡片 ---------- */
.cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
}
.card {
  padding: 24px 22px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  transition: transform 0.2s, border-color 0.2s, box-shadow 0.25s;
}
.card:hover {
  transform: translateY(-3px);
  border-color: color-mix(in srgb, var(--brand) 42%, var(--line));
  box-shadow: 0 24px 44px -34px var(--brand);
}
.ico {
  width: 40px;
  height: 40px;
  display: grid;
  place-items: center;
  font-size: 19px;
  border-radius: 11px;
  background: color-mix(in srgb, var(--brand) 14%, transparent);
  border: 1px solid color-mix(in srgb, var(--brand) 22%, transparent);
  margin-bottom: 14px;
}
.card h3 { margin: 0 0 8px; font-size: 17px; }
.card p { margin: 0; color: var(--text-2); font-size: 14.5px; }

/* ---------- 为什么 ---------- */
.why-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
}
.why {
  position: relative;
  padding: 28px 24px;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: var(--surface);
  overflow: hidden;
}
.why-n {
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.08em;
  color: color-mix(in srgb, var(--brand) 85%, #fff);
}
.why h3 { margin: 10px 0 8px; font-size: 18px; }
.why p { margin: 0; font-size: 14.5px; color: var(--text-2); }

.quotes {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
  margin-top: 20px;
}
.quote {
  margin: 0;
  padding: 22px;
  border-radius: var(--radius);
  border: 1px dashed var(--line);
  background: color-mix(in srgb, var(--surface) 60%, transparent);
}
.quote blockquote {
  margin: 0 0 12px;
  font-size: 15px;
  line-height: 1.7;
  color: var(--text);
}
.quote blockquote::before { content: "“"; color: var(--brand); font-size: 22px; line-height: 0; vertical-align: -4px; margin-right: 2px; }
.quote figcaption { font-size: 12.5px; color: var(--text-3); }
.quotes-note { margin: 14px 0 0; font-size: 12px; color: var(--text-3); }

/* ---------- 怎么开始 ---------- */
.steps {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
}
.steps.three { grid-template-columns: repeat(3, 1fr); }
.steps li {
  display: flex;
  gap: 13px;
  padding: 22px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}
.step-n {
  flex: none;
  width: 26px;
  height: 26px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-size: 13px;
  font-weight: 700;
  background: color-mix(in srgb, var(--brand) 20%, transparent);
  color: color-mix(in srgb, var(--brand) 85%, #fff);
}
.steps h4 { margin: 2px 0 6px; font-size: 15.5px; }
.steps p { margin: 0; font-size: 14px; color: var(--text-2); }

.start-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
  margin-top: 34px;
}
.notice {
  max-width: 760px;
  margin: 34px auto 0;
  padding: 16px 20px;
  border-radius: 12px;
  border: 1px solid var(--line);
  background: color-mix(in srgb, var(--warn) 8%, var(--surface));
  font-size: 14px;
  color: var(--text-2);
}
.notice strong { color: var(--text); }

/* ---------- FAQ ---------- */
.qa {
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--surface);
  padding: 4px 20px;
  margin-bottom: 12px;
}
.qa summary {
  cursor: pointer;
  padding: 15px 0;
  font-weight: 600;
  font-size: 15.5px;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
}
.qa summary::-webkit-details-marker { display: none; }
.qa summary::after {
  content: "+";
  color: var(--text-3);
  font-size: 20px;
  line-height: 1;
}
.qa[open] summary::after { content: "−"; color: var(--brand); }
.qa p { margin: 0 0 16px; color: var(--text-2); font-size: 15px; }

/* ---------- 结尾 / 页脚 ---------- */
.cta {
  padding: 88px 0;
  background:
    radial-gradient(ellipse 60% 120% at 50% 0%, color-mix(in srgb, var(--brand) 22%, transparent), transparent 70%),
    var(--bg);
  border-top: 1px solid var(--line);
  text-align: center;
}
.cta h2 { margin: 0 0 10px; font-size: clamp(24px, 3.2vw, 34px); }
.cta p { margin: 0; color: var(--text-2); }

.foot { border-top: 1px solid var(--line); background: var(--bg-alt); padding: 54px 0 26px; }
.foot-inner { display: grid; grid-template-columns: 1.1fr 1.6fr; gap: 40px; }
.foot-brand { display: flex; gap: 12px; align-items: flex-start; }
.foot-brand b { font-size: 15px; }
.foot-brand p { margin: 3px 0 0; font-size: 13px; color: var(--text-3); }
.foot-cols { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.foot-cols h5 { margin: 0 0 12px; font-size: 13px; color: var(--text-3); font-weight: 600; }
.foot-cols a { display: block; font-size: 14px; color: var(--text-2); padding: 4px 0; }
.foot-cols a:hover { color: var(--text); }
.foot-bottom {
  margin-top: 40px;
  padding-top: 20px;
  border-top: 1px solid var(--line);
  display: flex;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
  font-size: 12.5px;
  color: var(--text-3);
}

/* ---------- 滚动入场 ---------- */
.reveal { opacity: 0; transform: translateY(16px); }
.reveal.in { opacity: 1; transform: none; transition: opacity 0.6s ease, transform 0.6s ease; }

/* 打印/导出时内容必须完整可见 */
@media print {
  .nav, .mobile-menu, .nav-toggle, .hero-glow { display: none !important; }
  .reveal { opacity: 1 !important; transform: none !important; }
  .section, .cta { break-inside: avoid; }
}

/* ---------- 响应式 ---------- */
@media (max-width: 980px) {
  .cards, .why-grid, .quotes { grid-template-columns: repeat(2, 1fr); }
  .steps, .steps.three { grid-template-columns: repeat(2, 1fr); }
  .kefu-grid { grid-template-columns: 1fr; gap: 32px; }
  .phone { max-width: 420px; margin: 0 auto; }
  .foot-inner { grid-template-columns: 1fr; gap: 28px; }
}
@media (max-width: 760px) {
  .nav-links { display: none; }
  .nav-toggle { display: flex; }
  .mobile-menu[hidden] { display: none; }
  .mobile-menu:not([hidden]) { display: flex; }
  .hero { padding: 56px 0 52px; }
  .section { padding: 68px 0; }
  .cards, .why-grid, .quotes, .steps, .steps.three, .foot-cols { grid-template-columns: 1fr; }
  .stats { grid-template-columns: repeat(2, 1fr); row-gap: 20px; }
  .chat-demo { margin-top: 32px; }
  .bubble { max-width: 92%; font-size: 14px; }
  .sec-head { text-align: left !important; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: 0.001ms !important; transition-duration: 0.001ms !important; }
  .reveal { opacity: 1; transform: none; }
}