/* ──────────────────────────────────────────────────────────────
   AtomVoice — Tesla 风格视觉系统
   基线：纯白底、单一蓝色 CTA、Carbon Dark 文本、无阴影无渐变、
   字重 400/500、字距 normal、4px 微圆角、每屏一信息。
   ────────────────────────────────────────────────────────────── */

/* ── Reset ───────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

/* ── Tokens ──────────────────────────────────────────────────── */
:root {
  /* 色板 — 严格对应 Tesla DESIGN.md */
  --blue:        #3E6AE1;          /* Electric Blue：唯一彩色，仅用于主 CTA */
  --carbon:      #171A20;          /* Carbon Dark：主标题与导航 */
  --graphite:    #393C41;          /* Graphite：正文 */
  --pewter:      #5C5E62;          /* Pewter：三级文字、次级链接 */
  --silver:      #8E8E8E;          /* Silver Fog：占位 */
  --cloud:       #EEEEEE;          /* Cloud Gray：分割线 */
  --ash:         #F4F4F4;          /* Light Ash：替代浅底 */
  --white:       #FFFFFF;
  --frost:       rgba(255,255,255,0.75);

  /* 字体 */
  --font: "Universal Sans Text", "Universal Sans Display",
          -apple-system, BlinkMacSystemFont, "Helvetica Neue", Arial, sans-serif;
  --font-display: "Universal Sans Display", "Universal Sans Text",
                  -apple-system, BlinkMacSystemFont, "Helvetica Neue", Arial, sans-serif;
  --mono: "SF Mono", Menlo, Monaco, Consolas, monospace;

  /* 几何 */
  --r-btn:       4px;
  --r-card:      12px;
  --nav-h:       56px;

  /* 动效 — Tesla 统一 0.33s */
  --t: 0.33s;
}

/* ── Base ────────────────────────────────────────────────────── */
html { scroll-behavior: smooth; }
body {
  font-family: var(--font);
  font-size: 14px;
  font-weight: 400;
  line-height: 1.45;
  color: var(--graphite);
  background: var(--white);
  -webkit-font-smoothing: antialiased;
}

/* ── Nav：浮于 hero 上方，无阴影、无边框 ───────────────────── */
.nav {
  position: sticky; top: 0; z-index: 100;
  height: var(--nav-h);
  background: var(--frost);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
}
.nav-inner {
  max-width: 1383px; margin: 0 auto;
  height: 100%;
  display: flex; align-items: center; justify-content: space-between;
  padding: 0 32px;
}
.nav-brand {
  display: flex; align-items: center; gap: 10px;
  text-decoration: none; color: var(--carbon);
  font-size: 14px; font-weight: 500;
  line-height: 1;
}
.nav-brand img { display: block; }
.nav-right { display: flex; align-items: center; gap: 24px; }
.nav-download {
  text-decoration: none; color: var(--carbon);
  font-size: 14px; font-weight: 500;
  padding: 4px 16px;
  border-radius: var(--r-btn);
  transition: background-color var(--t), color var(--t);
}
.nav-download:hover { background: rgba(0,0,0,0.04); }

/* 语言切换 — 走 Pewter 文字链路 */
.lang-switcher {
  display: flex; align-items: center; gap: 2px;
}
.lang-btn {
  background: none; border: none; cursor: pointer;
  font-family: var(--font); font-size: 12px; font-weight: 500;
  color: var(--pewter);
  padding: 4px 6px;
  border-radius: var(--r-btn);
  transition: color var(--t), background-color var(--t);
  line-height: 1;
}
.lang-btn:hover { color: var(--carbon); }
.lang-btn.active { color: var(--carbon); background: rgba(0,0,0,0.05); }

/* ── Hero：全视口、留白主导 ────────────────────────────────── */
.hero {
  position: relative;
  min-height: calc(100vh - var(--nav-h));
  background: var(--white);
  display: flex; flex-direction: column;
  align-items: center; justify-content: center;
  padding: 96px 24px 96px;
  text-align: center;
  overflow: hidden;
}
.hero-inner {
  width: 100%;
  display: flex; flex-direction: column; align-items: center;
}
.hero-icon {
  width: 144px; height: 144px;
  margin-bottom: 40px;
  /* Tesla 不用阴影；图标本身有形即可 */
}
.hero-name h1 {
  font-family: var(--font-display);
  font-size: 40px; font-weight: 500;
  line-height: 1.2;
  letter-spacing: normal;
  color: var(--carbon);
  margin-bottom: 12px;
}
.hero-sub {
  font-size: 16px; font-weight: 400;
  color: var(--graphite);
  line-height: 1.45;
  margin-bottom: 8px;
}
.hero-tag {
  font-size: 14px; font-weight: 400;
  color: var(--pewter);
  max-width: 520px;
  line-height: 1.45;
}
.hero-btns {
  margin-top: 40px;
  display: flex; gap: 12px; flex-wrap: wrap; justify-content: center;
}
.hero-req {
  margin-top: 24px;
  font-size: 12px; color: var(--pewter);
}

/* ── Buttons：4px 圆角，0.33s 色彩过渡 ─────────────────────── */
.btn {
  display: inline-flex; align-items: center; justify-content: center;
  min-height: 40px;
  min-width: 200px;
  padding: 4px 24px;
  border-radius: var(--r-btn);
  font-family: var(--font);
  font-size: 14px; font-weight: 500;
  text-decoration: none; cursor: pointer;
  border: 1px solid transparent;
  transition: background-color var(--t), color var(--t), border-color var(--t);
  white-space: nowrap;
}
.btn-primary {
  background: var(--blue); color: var(--white);
}
.btn-primary:hover { background: #3458c4; }

.btn-ghost {
  background: rgba(244,244,244,0.65);
  color: var(--carbon);
  border-color: rgba(244,244,244,0.65);
}
.btn-ghost:hover { background: rgba(244,244,244,0.85); }

.btn-outline {
  background: transparent;
  color: var(--carbon);
  border-color: var(--carbon);
}
.btn-outline:hover { background: var(--carbon); color: var(--white); }

/* ── Sections：每屏一信息 ──────────────────────────────────── */
.section {
  padding: 120px 24px;
  background: var(--white);
}
.section-grey  { background: var(--ash); }
.section-white { background: var(--white); }
.section-dark  { background: var(--carbon); color: var(--white); }

.container { max-width: 1100px; margin: 0 auto; }

.section-title {
  font-family: var(--font-display);
  font-size: 32px; font-weight: 500;
  line-height: 1.2; letter-spacing: normal;
  color: var(--carbon);
  text-align: center;
  margin-bottom: 64px;
}
.section-title.light { color: var(--white); }

/* ── Card 基础：无阴影、无边框 ─────────────────────────────── */
.card {
  background: transparent;
  border: none;
  box-shadow: none;
  padding: 0;
}

/* ── Highlights：左右两栏，留白承担分组 ───────────────────── */
.highlights {
  display: grid; grid-template-columns: 1fr 1fr; gap: 64px;
  max-width: 1100px; margin: 0 auto;
}
.highlight-card { padding: 0; text-align: center; }
.highlight-card .card-icon {
  display: block;
  font-size: 32px;
  margin-bottom: 24px;
  filter: grayscale(1);   /* 收敛色彩，让蓝色 CTA 独显 */
}
.highlight-card h3 {
  font-family: var(--font-display);
  font-size: 24px; font-weight: 500;
  letter-spacing: normal;
  color: var(--carbon);
  margin-bottom: 12px;
}
.highlight-card p {
  color: var(--graphite);
  font-size: 14px;
  line-height: 1.55;
  max-width: 360px;
  margin: 0 auto;
}

/* ── Engines：3 列，纯文本排版 ─────────────────────────────── */
.engines {
  display: grid; grid-template-columns: repeat(3, 1fr); gap: 48px;
}
.engine-card {
  padding: 32px 0;
  border-top: 1px solid var(--cloud);
}
.engine-header {
  display: flex; align-items: center; gap: 12px;
  flex-wrap: wrap; margin-bottom: 16px;
}
.engine-icon   { font-size: 18px; filter: grayscale(1); }
.engine-name   {
  font-size: 17px; font-weight: 500;
  color: var(--carbon);
}
.engine-card p {
  color: var(--graphite);
  font-size: 14px; line-height: 1.55;
}

/* Badges — 极简，纯文字色 */
.badge {
  font-size: 11px; font-weight: 500;
  letter-spacing: normal;
  text-transform: none;
  padding: 2px 8px;
  border-radius: var(--r-btn);
  border: 1px solid var(--cloud);
  color: var(--pewter);
  background: transparent;
}
.badge-default { color: var(--blue); border-color: var(--blue); }
.badge-offline { color: var(--carbon); border-color: var(--carbon); }
.badge-cloud   { color: var(--pewter); border-color: var(--cloud); }

/* ── Features：纯列表式 ─────────────────────────────────────── */
.features-grid {
  display: grid; grid-template-columns: repeat(4, 1fr);
  gap: 0;
  list-style: none;
  max-width: 1100px; margin: 0 auto;
  border-top: 1px solid var(--cloud);
}
.features-grid li {
  padding: 24px 20px;
  font-size: 14px;
  color: var(--graphite);
  display: flex; align-items: center; gap: 12px;
  border-bottom: 1px solid var(--cloud);
}
.features-grid li::before {
  content: "";
  width: 6px; height: 6px;
  border-radius: 50%;
  background: var(--carbon);
  flex-shrink: 0;
}

/* ── Download：暗底 section，主 CTA 仍是蓝 ─────────────────── */
.section-dark .section-title { color: var(--white); }
.dl-desc {
  text-align: center;
  color: rgba(255,255,255,0.65);
  font-size: 14px;
  margin-bottom: 48px;
}
.dl-btns {
  display: flex; flex-wrap: wrap; justify-content: center; gap: 12px;
  margin-bottom: 48px;
}
.dl-btn { /* 沿用 .btn 尺寸 */ }
.section-dark .btn-outline {
  color: var(--white);
  border-color: var(--white);
}
.section-dark .btn-outline:hover {
  background: var(--white); color: var(--carbon);
}

.dl-alt { text-align: center; }
.dl-details summary {
  cursor: pointer; list-style: none;
  display: inline-block;
  color: rgba(255,255,255,0.55);
  font-size: 13px;
  padding: 6px 14px;
  border-radius: var(--r-btn);
  transition: color var(--t);
}
.dl-details summary::-webkit-details-marker { display: none; }
.dl-details summary:hover { color: var(--white); }
.dl-details[open] summary { color: rgba(255,255,255,0.75); }
.dl-details pre {
  margin-top: 16px; display: inline-block; text-align: left;
  background: rgba(255,255,255,0.06);
  border: 1px solid rgba(255,255,255,0.12);
  border-radius: var(--r-btn);
  padding: 16px 20px;
}
.dl-details code {
  font-family: var(--mono); font-size: 13px;
  color: rgba(255,255,255,0.82);
  white-space: pre;
}

/* ── Privacy page ────────────────────────────────────────────── */
.privacy-page {
  max-width: 640px; margin: 0 auto;
  padding: 96px 24px 120px;
}
.privacy-page h1 {
  font-family: var(--font-display);
  font-size: 40px; font-weight: 500;
  letter-spacing: normal;
  color: var(--carbon);
  margin-bottom: 12px;
}
.privacy-page .subtitle {
  color: var(--pewter); margin-bottom: 48px; font-size: 14px;
}
.lang-list {
  display: flex; flex-direction: column; gap: 0;
  list-style: none;
  border-top: 1px solid var(--cloud);
}
.lang-list li a {
  display: flex; align-items: center; justify-content: space-between;
  padding: 20px 4px;
  border-bottom: 1px solid var(--cloud);
  text-decoration: none; color: var(--carbon);
  font-size: 15px; font-weight: 500;
  transition: color var(--t);
}
.lang-list li a:hover { color: var(--blue); }
.lang-list .lang-label {
  color: var(--pewter); font-size: 12px; font-weight: 400;
  font-family: var(--mono);
}
.lang-list .arrow { display: none; }

/* ── Footer ──────────────────────────────────────────────────── */
.footer {
  background: var(--white);
  border-top: 1px solid var(--cloud);
  padding: 32px 24px;
}
.footer-inner {
  max-width: 1383px; margin: 0 auto;
  display: flex; flex-direction: column; align-items: center; gap: 16px;
}
.footer-links {
  display: flex; flex-wrap: wrap; justify-content: center; gap: 8px 32px;
}
.footer-links a {
  text-decoration: none; color: var(--pewter);
  font-size: 12px;
  transition: color var(--t);
}
.footer-links a:hover { color: var(--carbon); }
.footer-copy {
  font-size: 12px; color: var(--pewter);
}

/* ── Responsive ──────────────────────────────────────────────── */
@media (max-width: 960px) {
  .engines { grid-template-columns: 1fr 1fr; gap: 32px; }
  .features-grid { grid-template-columns: repeat(2, 1fr); }
  .highlights { gap: 48px; }
}
@media (max-width: 640px) {
  .section { padding: 80px 20px; }
  .hero-name h1 { font-size: 28px; }
  .hero-icon { width: 112px; height: 112px; margin-bottom: 32px; }
  .highlights { grid-template-columns: 1fr; gap: 56px; }
  .engines { grid-template-columns: 1fr; gap: 0; }
  .engine-card { padding: 24px 0; }
  .features-grid { grid-template-columns: 1fr; }
  .section-title { font-size: 24px; margin-bottom: 48px; }
  .hero-btns { flex-direction: column; width: 100%; max-width: 320px; }
  .btn { width: 100%; min-width: 0; }
  .dl-btns { flex-direction: column; align-items: center; }
  .dl-btn { width: 100%; max-width: 320px; }
  .nav-inner { padding: 0 16px; }
}
@media (max-width: 420px) {
  .nav-right { gap: 12px; }
  .nav-download { display: none; }
  .lang-btn { padding: 4px 4px; font-size: 11px; }
}