/* ============================================================
   OpenAI.com Design DNA — components.css
   依赖 tokens.css。类名刻意保持语义化（nav / hero / card / media /
   metric / prose / toc / footer），便于整体替换成 Tailwind、Vue、React。
   规则来自 22 页实测：按钮只有三档、卡片无阴影、边框仅 1px 发丝线、
   圆角 6.08px、hover 只做 4–6% 明度 / 下划线 / 1–2px 位移。
   ============================================================ */

*,
*::before,
*::after { box-sizing: border-box; }

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

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: var(--font-sans);
  font-size: var(--type-p1-size);
  line-height: var(--type-p1-line);
  letter-spacing: var(--type-p1-track);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3, h4, h5, h6, p, figure { margin: 0; }
h1, h2, h3, h4, h5, h6 { font-weight: 500; }
img, video, svg { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
ul { margin: 0; padding: 0; list-style: none; }
::selection { background: var(--fg); color: #fff; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* ---------- 布局容器 ---------- */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--gutter);
}
.section { padding-block: var(--section-y); }
.section--tight { padding-block: var(--section-y-tight); }
.section__head { display: flex; align-items: baseline; justify-content: space-between; gap: 24px; margin-bottom: 40px; }

.overline {
  font-size: var(--type-nav-header-size);
  line-height: var(--type-nav-header-line);
  font-weight: 500;
  color: var(--fg-60);
}

/* ---------- 顶栏 64px ---------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 50;
  height: var(--nav-h);
  background: rgba(255, 255, 255, 0.88);
  backdrop-filter: saturate(180%) blur(14px);
  -webkit-backdrop-filter: saturate(180%) blur(14px);
}
.nav__inner { display: flex; align-items: center; gap: 28px; height: 100%; }
.brand { display: inline-flex; align-items: center; gap: 8px; font-weight: 600; letter-spacing: -0.01em; }
.brand__mark { width: 22px; height: 22px; flex: none; color: var(--fg); }
.nav__links { display: flex; align-items: center; gap: 26px; font-size: var(--type-nav-size); font-weight: 500; }
.nav__links a { color: var(--fg); transition: opacity var(--dur-short) var(--ease-primary); }
.nav__links a:hover { text-decoration: underline; text-underline-offset: 5px; text-decoration-thickness: 1px; }
.nav__cta { margin-left: auto; display: flex; align-items: center; gap: 8px; }

/* ---------- 按钮：三档 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  height: 40px;
  padding: 0 20px;
  border: 1px solid transparent;
  border-radius: var(--radius-full);
  font-family: inherit;
  font-size: var(--type-p2-size);
  font-weight: 500;
  letter-spacing: -0.005em;
  white-space: nowrap;
  cursor: pointer;
  transition: background-color var(--dur-short) var(--ease-primary),
              border-color var(--dur-short) var(--ease-primary),
              transform var(--dur-short) var(--ease-primary);
}
.btn--primary { background: var(--fg); color: #fff; }
.btn--primary:hover { background: #1f1f1f; }
.btn--secondary { background: var(--surface); color: var(--fg); }
.btn--secondary:hover { background: #e8e8e8; }
.btn--outline { background: transparent; border-color: var(--line); color: var(--fg); }
.btn--outline:hover { background: rgba(0, 0, 0, 0.03); }
.btn--sm { height: 32px; padding: 0 14px; font-size: 13px; }
.btn:active { transform: translateY(1px); }

.link-arrow {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: var(--type-p2-size);
  font-weight: 500;
  border-bottom: 1px solid transparent;
  transition: border-color var(--dur-short) var(--ease-primary);
}
.link-arrow:hover { border-bottom-color: currentColor; }

/* ---------- 公告条（顶部 Event/New 条） ---------- */
.announce {
  background: linear-gradient(90deg, #eaf4ff 0%, #f7fbff 60%, #ffffff 100%);
  font-size: var(--type-p2-size);
  line-height: 1.5;
}
.announce--dark { background: #000; color: #fff; }
.announce__inner { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; min-height: 44px; padding-block: 8px; }
.chip {
  display: inline-flex;
  align-items: center;
  height: 22px;
  padding: 0 8px;
  border: 1px solid var(--line);
  border-radius: var(--radius-full);
  background: #fff;
  font-size: 12px;
  font-weight: 500;
  letter-spacing: 0;
}
.chip--accent { background: var(--accent); border-color: transparent; color: #fff; }

/* ---------- Hero ---------- */
.hero { padding-top: calc(var(--page-top-gap) + 56px); padding-bottom: var(--section-y); }
.hero--centered { text-align: center; }
.hero__title { margin-top: 16px; text-wrap: balance; }
.hero__sub {
  margin-top: 22px;
  max-width: 620px;
  color: var(--fg-60);
  font-size: var(--type-p1-size);
  line-height: var(--type-p1-line);
}
.hero--centered .hero__sub { margin-inline: auto; }
.hero__actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 32px; }
.hero--centered .hero__actions { justify-content: center; }
.hero--split { display: grid; grid-template-columns: 5fr 7fr; gap: 64px; align-items: center; }

/* ---------- 媒体块（DNA 的表现力主要在这里，不在版式） ---------- */
.media-rows { display: grid; grid-template-columns: 1fr 1fr; gap: var(--grid-gap); }
.media {
  position: relative;
  overflow: hidden;
  border-radius: var(--radius-md);
  background: var(--surface);
  aspect-ratio: 16 / 9;
}
.media > img,
.media > video { width: 100%; height: 100%; object-fit: cover; }
.media--warm { background: linear-gradient(135deg, #fd7131 0%, #f7a48a 55%, #ddafa4 100%); }
.media--cool { background: radial-gradient(120% 120% at 20% 0%, #a3b2fb 0%, #7680f6 45%, #393d54 100%); }
.media--paper { background: linear-gradient(180deg, #f8f8f5 0%, #eceae4 100%); }
.media__tag {
  position: absolute;
  left: 16px;
  bottom: 16px;
  display: inline-flex;
  align-items: center;
  height: 26px;
  padding: 0 10px;
  border-radius: var(--radius-full);
  background: rgba(255, 255, 255, 0.9);
  color: var(--fg);
  font-size: 12px;
  font-weight: 500;
}

/* ---------- 客户 logo 带：一律灰度 ---------- */
.logo-band {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 28px 52px;
  padding-block: 28px;
  border-block: 1px solid var(--line);
  color: var(--fg-44);
  font-weight: 600;
  font-size: 15px;
  letter-spacing: -0.01em;
}
.logo-band span { filter: grayscale(1); }

/* ---------- 卡片 ---------- */
.cards { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: var(--grid-gap); }
.cards--4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.cards--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.card {
  display: flex;
  flex-direction: column;
  gap: 12px;
  padding: 24px;
  border-radius: var(--radius-md);
  background: var(--card);
}
.card--plain { background: #fff; border: 1px solid var(--line); }
.card__title { font-size: var(--type-h4-size); line-height: var(--type-h4-line); letter-spacing: var(--type-h4-track); }
.card__body { color: var(--fg-60); font-size: var(--type-p2-size); line-height: var(--type-p2-line); }
.card__link { margin-top: auto; font-size: var(--type-p2-size); font-weight: 500; }

/* ---------- 指标墙（用数字替代长案例） ---------- */
.metrics {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: var(--grid-gap);
  padding-top: 32px;
  border-top: 1px solid var(--line);
}
.metric__value { font-size: clamp(2rem, 4vw, 3rem); font-weight: 500; letter-spacing: -0.03em; line-height: 1; }
.metric__label { margin-top: 10px; color: var(--fg-60); font-size: var(--type-p2-size); line-height: 1.45; }

/* ---------- 长文页：左侧粘性 TOC + 596px 正文 ---------- */
.article { display: grid; grid-template-columns: 220px minmax(0, 1fr); gap: 64px; max-width: 1100px; margin-inline: auto; }
.toc {
  position: sticky;
  top: calc(var(--nav-h) + 24px);
  align-self: start;
  font-size: 13px;
  line-height: 1.55;
  color: var(--fg-60);
}
.toc a { display: block; padding-block: 4px; }
.toc a:hover { color: var(--fg); }
.toc a[aria-current="true"] { color: var(--fg); font-weight: 500; }
.prose { max-width: var(--measure); }
.prose p + p { margin-top: 1.5em; }
.prose h2 { margin-top: 2em; margin-bottom: 0.5em; }
.prose blockquote { margin: 1.6em 0; font-weight: 700; }
.prose hr { margin-block: 40px; border: 0; border-top: 1px solid var(--line); }
.meta-row { display: flex; flex-wrap: wrap; align-items: center; gap: 12px; color: var(--fg-60); font-size: var(--type-p2-size); }
.meta-row .dot::before { content: "·"; margin-right: 12px; }

/* ---------- 表单页：5:7 分栏 ---------- */
.split-form { display: grid; grid-template-columns: 5fr 7fr; gap: 64px; align-items: start; }
.form-card {
  padding: 32px;
  border-radius: var(--radius-lg);
  background: #fff;
  box-shadow: var(--shadow-high);   /* 全站少数需要"浮起来"的场景 */
}
.field { display: grid; gap: 8px; margin-bottom: 16px; }
.field > label { font-size: var(--type-p2-size); font-weight: 500; }
.field > input,
.field > textarea {
  width: 100%;
  padding: 12px 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius-md);
  font: inherit;
  font-size: var(--type-p1-size);
  background: #fff;
}
.field > input:focus,
.field > textarea:focus { outline: none; border-color: var(--fg); }

/* ---------- 页脚 6 栏 ---------- */
.footer { padding-block: 64px 48px; border-top: 1px solid var(--line); font-size: var(--type-p2-size); }
.footer__grid { display: grid; grid-template-columns: repeat(6, minmax(0, 1fr)); gap: 24px; }
.footer__col h4 { margin-bottom: 12px; font-size: 13px; font-weight: 500; }
.footer__col a { display: block; padding-block: 4px; color: var(--fg-60); }
.footer__col a:hover { color: var(--fg); }
.footer__bottom { display: flex; flex-wrap: wrap; gap: 8px 24px; margin-top: 48px; color: var(--fg-44); }

/* ---------- 动效：淡入 + 12–24px 上移，一次性 ---------- */
.reveal {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity var(--dur-macro) var(--ease-primary), transform var(--dur-macro) var(--ease-primary);
}
.reveal.is-in { opacity: 1; transform: none; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.001ms !important; transition-duration: 0.001ms !important; }
  .reveal { opacity: 1; transform: none; }
}

/* ---------- 响应式（断点 1024 / 768） ---------- */
@media (max-width: 1024px) {
  .nav__links { display: none; }
  .cards, .cards--4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .metrics { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .footer__grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .hero--split, .split-form, .article { grid-template-columns: 1fr; gap: 32px; }
  .toc { position: static; display: flex; flex-wrap: wrap; gap: 0 16px; }
}

@media (max-width: 768px) {
  .container { padding-inline: 20px; }
  .cards, .cards--2, .cards--4, .metrics, .media-rows { grid-template-columns: 1fr; }
  .footer__grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .hero { padding-top: 32px; }
  .hero__actions .btn { flex: 1 1 auto; }
}