/* ============================================================
   A1tox.com — 品牌层样式
   基础层：dna-tokens.css（OpenAI 实测 token）+ dna-components.css（组件基线）
   本文件只做品牌差异：不重复定义 DNA 已有的 nav / card / btn / footer 骨架，
   仅覆盖差异项 + 新增首页专属组件。
   ============================================================ */

/* ---------- 0. 字体栈与工具类 ---------- */
:root {
  /* DNA 原栈以 OpenAI Sans 打头（不可分发）；换成本地可分发组合，
     字阶 / 字距 / 行高关系完全沿用 DNA */
  --font-sans: "Inter", "Noto Sans SC", -apple-system, "Segoe UI", Roboto,
    "PingFang SC", "Microsoft YaHei", sans-serif;
}

.visually-hidden {
  position: absolute;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

/* 无 JS / site.js 加载失败时，内容必须可见（基础层 .reveal 默认 opacity:0） */
.no-js .reveal { opacity: 1; transform: none; }

.skip-link {
  position: absolute; left: 16px; top: -60px; z-index: 100;
  padding: 10px 16px;
  background: var(--fg); color: #fff;
  border-radius: var(--radius-md);
  font-size: 14px;
  transition: top var(--dur-short) var(--ease-primary);
}
.skip-link:focus-visible { top: 12px; }

/* 超大标题（Hero / 收尾）：比 DNA 的 --type-xl 收一档 */
.t-display {
  font-size: clamp(2.6rem, 7.2vw, 4.6rem);
  line-height: 1.04;
  letter-spacing: -0.038em;
  font-weight: 500;
  text-wrap: balance;
}

/* ---------- 1. 导航品牌位 ---------- */
.brand { gap: 14px; }
.brand__logo { width: 96px; height: auto; }
.brand__divider { width: 1px; height: 16px; background: var(--line); }
.brand__entity {
  font-size: 13px; font-weight: 500; letter-spacing: 0.04em;
  color: var(--fg-60);
}
.nav__toggle {
  display: none;
  width: 40px; height: 40px;
  margin-left: auto; padding: 0;
  background: none; border: 0;
  cursor: pointer;
  flex-direction: column; justify-content: center; align-items: center; gap: 5px;
}
.nav__toggle span {
  display: block; width: 18px; height: 1.5px;
  background: var(--fg);
  transition: transform var(--dur-short) var(--ease-primary);
}
.nav__toggle[aria-expanded="true"] span:first-child { transform: translateY(3.25px) rotate(45deg); }
.nav__toggle[aria-expanded="true"] span:last-child { transform: translateY(-3.25px) rotate(-45deg); }

/* ---------- 2. Hero ---------- */
.hero--centered { padding-top: clamp(56px, 8vw, 104px); padding-bottom: 0; }
.hero__eyebrow {
  display: inline-block;
  font-size: 12px; font-weight: 500;
  letter-spacing: 0.18em;
  color: var(--fg-44);
  text-transform: uppercase;
}
.hero__title { margin-top: 24px; }
.hero__tagline {
  margin-top: 22px;
  font-size: 12.5px;
  font-weight: 500;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--fg-44);
}
.hero__sub {
  margin-top: 20px;
  font-size: clamp(1rem, 1.5vw, 1.25rem);
  line-height: 1.65;
  letter-spacing: -0.012em;
  color: var(--fg);
}
.hero__note {
  margin-top: 28px;
  font-size: 13px;
  font-weight: 500;
  color: var(--fg-44);
}
.hero__actions { margin-top: 36px; }
.hero--centered .hero__actions .btn { height: 48px; padding: 0 26px; font-size: 15px; }

/* 首屏渐变带（对齐 FDE）：纯白 → 极淡冷蓝，下缘一条发丝线切回纯白 */
.hero-band {
  background: linear-gradient(180deg, #ffffff 0%, #ffffff 42%, #f9fdff 74%, #f3f9fe 100%);
  border-bottom: 1px solid #ebebeb;
}
.hero--centered .hero__actions { align-items: center; gap: 22px; }
.hero__actions .link-arrow {
  padding: 12px 2px;
  font-size: 15px;
  gap: 7px;
  color: var(--fg);
  border-bottom: 0;
  transition: color var(--dur-short) var(--ease-primary);
}
/* 悬浮只渐灰：不加下划线，箭头也不位移 */
.hero__actions .link-arrow:hover { color: var(--fg-60); }
.link-arrow__icon {
  width: 14px;
  height: 14px;
  flex: 0 0 auto;
}

/* ---------- 3. 合作伙伴带（紧跟首屏） ---------- */
.partner-strip {
  margin-top: clamp(56px, 7vw, 96px);
  padding-bottom: clamp(40px, 7vw, 104px);
}
.partner-strip__inner {
  display: block;
  padding-block: 8px;
}
.partner-strip__label {
  font-size: 12.5px;
  font-weight: 500;
  letter-spacing: 0.14em;
  color: var(--fg-44);
}

/* 合作伙伴：每个格子上下翻牌轮换 logo（同 openai.com/fde 的做法） */
.logo-swap {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 16px;
  align-items: center;
}
.logo-swap__cell {
  position: relative;
  height: 52px;
}
.logo-swap__layer {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  opacity: 0;
  transform: translateY(var(--logo-slide, 26px));
  transition: opacity 0.5s var(--ease-primary), transform 0.5s var(--ease-primary);
  will-change: transform, opacity;
}
.logo-swap__layer.is-active { opacity: 1; transform: translateY(0); }
.logo-swap__layer.is-out { opacity: 0; transform: translateY(calc(-1 * var(--logo-slide, 26px))); }
.logo-swap__layer.is-reset { transition: none; }
.logo-swap__layer img {
  height: 30px;
  width: auto;
  max-width: none;
  flex: 0 0 auto;
  object-fit: contain;
}
.logo-swap__text,
.logo-swap__text--name {
  font-size: 16px;
  flex: 0 0 auto;
  font-weight: 600;
  letter-spacing: 0.05em;
  color: var(--fg);
  white-space: nowrap;
}
/* 纯文字标：品牌名用页面字重压住，字距略收紧 */
.logo-swap__text--name {
  font-size: 19px;
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--fg);
}

@media (prefers-reduced-motion: reduce) {
  .logo-swap__layer { transition: none; }
}

@media (max-width: 1024px) {
  .partner-strip__inner { grid-template-columns: 1fr; gap: 12px; }
  .logo-swap { grid-template-columns: repeat(3, minmax(0, 1fr)); row-gap: 12px; }
}

@media (max-width: 768px) {
  .logo-swap { grid-template-columns: repeat(2, minmax(0, 1fr)); row-gap: 16px; }
  /* 移动端只留 4 个标识：2 列 × 2 排 */
  .logo-swap__cell:nth-child(n + 5) { display: none; }
  .logo-swap__cell { height: 40px; }
  .logo-swap__layer img { height: 22px; }
  .logo-swap__text { font-size: 13px; }
}

/* ---------- 4. 立场段 ---------- */
.statement { padding-block: clamp(72px, 8vw, 120px) clamp(48px, 5vw, 72px); }
.statement__title {
  max-width: 22em;
  letter-spacing: -0.03em;
  line-height: 1.3;
}
.statement__lead {
  max-width: 760px;
  margin-top: 24px;
  font-size: clamp(1rem, 1.3vw, 1.125rem);
  line-height: 1.8;
  color: var(--fg-60);
}
.statement__lead strong { color: var(--fg); font-weight: 500; }
.cards--3 { grid-template-columns: repeat(3, minmax(0, 1fr)); margin-top: 48px; }
.card--flat { background: var(--surface); }
.card__index {
  font-size: 12px; font-weight: 500;
  letter-spacing: 0.06em;
  color: var(--fg-44);
}
.card__title { font-size: 18px; line-height: 1.4; letter-spacing: -0.015em; }
.card__body { font-size: 14px; line-height: 1.7; }

/* ---------- 5. 主视觉（全宽出血图） ---------- */
.bleed { padding-top: clamp(48px, 5vw, 72px); }
.bleed__media {
  position: relative;
  margin: 0;
  border-radius: var(--radius-md);
  overflow: hidden;
  background: #0a0a0a;
}
.bleed__media img { width: 100%; height: auto; display: block; }
.bleed__caption {
  position: absolute;
  inset: auto 0 0 0;
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 24px;
  padding: clamp(24px, 4vw, 48px);
  background: linear-gradient(to top, rgba(0, 0, 0, 0.72) 0%, rgba(0, 0, 0, 0) 100%);
  color: #fff;
}
.bleed__quote {
  font-size: clamp(1.25rem, 2.4vw, 2rem);
  font-weight: 500;
  line-height: 1.35;
  letter-spacing: -0.025em;
}
.bleed__meta {
  flex-shrink: 0;
  font-size: 12px; font-weight: 500;
  letter-spacing: 0.14em;
  color: rgba(255, 255, 255, 0.6);
  text-transform: uppercase;
}

/* ---------- 6. FDE ---------- */
.fde__title { margin-top: 16px; letter-spacing: -0.032em; }
.fde__lead {
  max-width: 660px;
  margin-top: 20px;
  font-size: clamp(1rem, 1.3vw, 1.125rem);
  line-height: 1.75;
  color: var(--fg-60);
}

.pipeline {
  margin-block: 0;
  padding: 0;
  list-style: none;
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 4px;
  margin-top: clamp(40px, 5vw, 56px);
}
.pipeline__step {
  display: flex;
  flex-direction: column;
  gap: 0;
  padding: 26px 20px 28px;
  background: var(--surface);
  border-radius: var(--radius-md);
  transition: background var(--dur-short) var(--ease-primary);
}
.pipeline__step:hover { background: var(--n-5); }
.pipeline__no {
  font-size: 12px; font-weight: 500;
  letter-spacing: 0.06em;
  color: var(--fg-44);
}
.pipeline__title {
  margin-top: 18px;
  font-size: 17px; font-weight: 500;
  letter-spacing: -0.015em;
}
.pipeline__cn {
  margin-top: 2px;
  font-size: 13px; font-weight: 500;
  color: var(--fg-44);
}
.pipeline__body {
  margin-top: 16px;
  font-size: 13px; line-height: 1.65;
  color: var(--fg-60);
}

.fde__foot {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 20px;
  margin-top: 32px;
}
.fde__note { font-size: 13px; color: var(--fg-44); }

/* ---------- 7. 案例演示 ---------- */
.demo { margin-top: 40px; }
.demo__switch { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 20px; }
.demo__tab {
  padding: 9px 18px;
  font: inherit;
  font-size: 13.5px; font-weight: 500;
  color: var(--fg-60);
  background: var(--surface);
  border: 1px solid transparent;
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: background var(--dur-short) var(--ease-primary),
              color var(--dur-short) var(--ease-primary);
}
.demo__tab:hover { background: var(--n-5); }
.demo__tab.is-active { background: var(--fg); color: #fff; }

.demo__stage {
  display: grid;
  grid-template-columns: 340px minmax(0, 1fr);
  gap: 20px;
  align-items: stretch;
  outline: none;
}
.demo__stage:focus-visible { outline: 2px solid var(--accent); outline-offset: 4px; border-radius: var(--radius-md); }

/* --- 手机 / 微信 --- */
.phone {
  display: flex; flex-direction: column;
  min-height: 480px;
  background: #ededed;
  border: 1px solid var(--line);
  border-radius: 20px;
  overflow: hidden;
}
.phone__top {
  display: grid;
  grid-template-columns: 16px 1fr 24px;
  align-items: center;
  gap: 8px;
  padding: 12px 16px;
  background: #f7f7f7;
  border-bottom: 1px solid rgba(0, 0, 0, 0.06);
}
.phone__back { font-size: 18px; color: var(--n-10); line-height: 1; }
.phone__title { font-size: 14px; font-weight: 500; text-align: center; }
.phone__more { font-size: 11px; color: var(--n-10); text-align: right; letter-spacing: 0.05em; }
.phone__chat {
  flex: 1;
  display: flex; flex-direction: column; gap: 10px;
  padding: 16px 14px;
  overflow-y: auto;
}
.phone__msg {
  max-width: 86%;
  padding: 9px 12px;
  font-size: 13.5px; line-height: 1.55;
  border-radius: 6px;
  opacity: 0;
  transform: translateY(6px);
  animation: msg-in var(--dur-medium) var(--ease-primary) forwards;
}
@keyframes msg-in { to { opacity: 1; transform: none; } }
.phone__msg--out { align-self: flex-end; background: #95ec69; color: #111; }
.phone__msg--in  { align-self: flex-start; background: #fff; color: #111; }
.phone__msg--meta {
  align-self: center;
  background: transparent;
  color: var(--fg-44);
  font-size: 11.5px;
  padding: 2px 0;
  text-align: center;
}
.phone__msg--file {
  align-self: flex-start;
  display: flex; align-items: center; gap: 10px;
  width: 84%;
  background: #fff;
  padding: 10px 12px;
}
.phone__file-icon {
  flex-shrink: 0;
  display: grid; place-items: center;
  width: 32px; height: 32px;
  border-radius: 4px;
  background: #ececec;
  font-size: 10px; font-weight: 600;
  color: #555;
  letter-spacing: 0.02em;
}
.phone__file-meta { min-width: 0; display: flex; flex-direction: column; gap: 2px; }
.phone__file-name {
  font-size: 13px; font-weight: 500;
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.phone__file-size { margin-top: 0; font-size: 11px; color: var(--fg-44); }

.phone__input { margin-top: auto; }
.phone__voice {
  display: flex;
  align-items: center; justify-content: center; gap: 8px;
  width: calc(100% - 28px);
  margin: 12px 14px;
  padding: 11px 16px;
  font: inherit; font-size: 14px; font-weight: 500;
  color: var(--fg);
  background: #fff;
  border: 1px solid rgba(0, 0, 0, 0.1);
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: background var(--dur-short) var(--ease-primary);
}
.phone__voice:hover { background: #f2f2f2; }
.phone__voice[aria-disabled="true"] { cursor: default; opacity: 0.55; }
.phone__voice-ico {
  width: 14px; height: 14px;
  border: 1.5px solid var(--n-10);
  border-radius: 50%;
  position: relative;
}
.phone__voice-ico::after {
  content: "";
  position: absolute; inset: 3px;
  border-radius: 50%;
  background: var(--n-10);
}
.phone__wave { display: none; align-items: center; gap: 2px; height: 14px; color: var(--fg); }
.phone__wave i {
  display: block; width: 2px; height: 100%;
  background: currentColor;
  transform-origin: center;
  animation: wave 0.8s ease-in-out infinite;
}
.phone__wave i:nth-child(2) { animation-delay: 0.08s; }
.phone__wave i:nth-child(3) { animation-delay: 0.16s; }
.phone__wave i:nth-child(4) { animation-delay: 0.24s; }
.phone__wave i:nth-child(5) { animation-delay: 0.32s; }
.phone__wave i:nth-child(6) { animation-delay: 0.4s; }
.phone__wave i:nth-child(7) { animation-delay: 0.48s; }
@keyframes wave { 0%, 100% { transform: scaleY(0.25); } 50% { transform: scaleY(1); } }
.phone__voice.is-live { background: #e4e4e4; }
.phone__voice.is-live .phone__voice-ico { display: none; }
.phone__voice.is-live .phone__wave { display: flex; }

/* --- 电脑 / DSH --- */
.agent {
  display: flex; flex-direction: column;
  min-height: 480px;
  background: #0a0a0a;
  border-radius: 6px;
  overflow: hidden;
  color: #fff;
}
.agent__bar {
  display: flex; align-items: center; gap: 10px;
  padding: 12px 16px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}
.agent__dot {
  width: 7px; height: 7px; border-radius: 50%;
  background: rgba(255, 255, 255, 0.3);
}
.agent.is-running .agent__dot {
  background: #fff;
  animation: pulse 1.1s ease-in-out infinite;
}
@keyframes pulse { 0%, 100% { opacity: 1; } 50% { opacity: 0.25; } }
.agent__name {
  font-family: var(--font-mono);
  font-size: 12px; font-weight: 500;
  letter-spacing: 0.1em;
}
.agent__state {
  margin-left: auto;
  font-family: var(--font-mono);
  font-size: 11.5px;
  color: rgba(255, 255, 255, 0.45);
}
.agent__log {
  margin: 0;
  padding: 18px 16px;
  list-style: none;
  flex: 1;
  display: flex; flex-direction: column; gap: 2px;
  font-family: var(--font-mono);
  font-size: 12.5px; line-height: 1.5;
  overflow-y: auto;
}
.agent__line {
  display: flex; gap: 10px;
  padding: 5px 0;
  color: rgba(255, 255, 255, 0.55);
  opacity: 0;
  transform: translateX(-4px);
  animation: line-in var(--dur-medium) var(--ease-primary) forwards;
}
@keyframes line-in { to { opacity: 1; transform: none; } }
.agent__line.is-active { color: rgba(255, 255, 255, 0.95); }
.agent__mark {
  flex-shrink: 0;
  width: 14px;
  text-align: center;
  color: rgba(255, 255, 255, 0.4);
}
.agent__line.is-active .agent__mark::after {
  content: "";
  display: inline-block;
  width: 6px; height: 6px;
  border: 1px solid rgba(255, 255, 255, 0.8);
  border-top-color: transparent;
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
  vertical-align: middle;
}
.agent__line.is-done .agent__mark::after { content: "✓"; color: rgba(255, 255, 255, 0.72); }
@keyframes spin { to { transform: rotate(360deg); } }
.agent__time { flex-shrink: 0; color: rgba(255, 255, 255, 0.3); }
.agent__text { min-width: 0; word-break: break-word; }

.agent__result {
  margin: 0 16px 16px;
  padding: 16px;
  border: 1px solid rgba(255, 255, 255, 0.16);
  border-radius: 6px;
  background: rgba(255, 255, 255, 0.04);
  opacity: 0;
  transform: translateY(6px);
  animation: line-in var(--dur-medium) var(--ease-primary) forwards;
}
.agent__result-title {
  font-size: 13px; font-weight: 500;
  color: #fff;
}
.agent__result-body {
  margin-top: 10px;
  font-family: var(--font-mono);
  font-size: 12px; line-height: 1.7;
  color: rgba(255, 255, 255, 0.58);
  white-space: pre-wrap;
}

.demo__foot {
  margin-top: 18px;
  font-size: 12.5px;
  color: var(--fg-44);
}

/* ---------- 8. 规模 ---------- */
.scales {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: var(--grid-gap);
  margin-top: clamp(40px, 5vw, 56px);
}
.scale {
  display: flex; flex-direction: column;
  padding: 32px 28px 28px;
  background: var(--card);
  border-radius: var(--radius-md);
}
.scale__size {
  font-size: clamp(2.5rem, 3.6vw, 3.25rem);
  font-weight: 500;
  letter-spacing: -0.04em;
  line-height: 1;
}
.scale__size span {
  margin-left: 4px;
  font-size: 13px; font-weight: 500;
  letter-spacing: 0;
  color: var(--fg-60);
}
.scale__label { margin-top: 14px; font-size: 14px; font-weight: 500; }
.scale__body  { margin-top: 14px; margin-bottom: 20px; font-size: 14px; line-height: 1.7; color: var(--fg-60); }
.scale__out {
  margin-top: auto;
  padding-top: 20px;
  font-size: 12.5px;
  color: var(--fg-44);
  border-top: 1px solid var(--line);
}

/* ---------- 9. 工作室 ---------- */
.studio {
  display: grid;
  grid-template-columns: 340px minmax(0, 1fr);
  gap: clamp(32px, 5vw, 72px);
  align-items: start;
}
.studio__quote {
  margin: 0 0 36px;
  padding-left: 24px;
  border-left: 2px solid var(--fg);
  font-size: clamp(1.25rem, 1.9vw, 1.5rem);
  font-weight: 500;
  line-height: 1.5;
  letter-spacing: -0.02em;
}
.studio__body p {
  max-width: 620px;
  font-size: 1rem; line-height: 1.8;
  color: var(--fg-60);
}
.studio__body p + p { margin-top: 20px; }
.studio__body strong { color: var(--fg); font-weight: 500; }

/* ---------- 10. 收尾 ---------- */
.cta {
  text-align: center;
  padding-block: clamp(24px, 4vw, 48px) clamp(32px, 5vw, 64px);
  border-top: 1px solid var(--line);
}
.cta__title {
  margin-top: 20px;
  line-height: 1.14;
  letter-spacing: -0.035em;
}
.cta__sub {
  max-width: 620px;
  margin: 24px auto 0;
  font-size: clamp(1rem, 1.3vw, 1.125rem);
  line-height: 1.75;
  color: var(--fg-60);
}
.cta__sub em {
  font-style: normal;
  padding-bottom: 2px;
  border-bottom: 1px solid var(--n-7);
  color: var(--fg);
}
.cta__actions {
  display: flex; flex-wrap: wrap; gap: 12px; justify-content: center;
  margin-top: 36px;
}
.cta__actions .btn { height: 48px; padding: 0 26px; font-size: 15px; }
.cta__note { margin-top: 24px; font-size: 13px; color: var(--fg-44); }

/* ---------- 11. 页脚（DNA 为 6 栏，这里 4 栏 + 品牌列） ---------- */
.footer { margin-top: 0; padding-block: 64px 32px; border-top: 0; }
.footer__grid { grid-template-columns: 2.2fr 1fr 1fr 1fr; gap: 40px; }
.footer__logo { width: 84px; height: auto; margin-bottom: 16px; }
.footer__col--brand p { font-size: 13.5px; line-height: 1.7; color: var(--fg-60); }
.footer__entity { margin-top: 6px; font-size: 12.5px !important; color: var(--fg-44) !important; }
.footer__col h3 {
  margin-bottom: 14px;
  font-size: 13px; font-weight: 500;
  color: var(--fg-44);
}
.footer__col a { font-size: 13.5px; }
.footer__muted { margin-top: 2px; font-size: 13px; color: var(--fg-44); }
.footer__bottom { margin-top: 48px; padding-top: 24px; border-top: 1px solid var(--line); }

/* ---------- 12. 响应式 ---------- */
/* 基础层在 ≤1024 隐藏主导航；这里用 min-width 显式声明，避免依赖加载顺序 */
@media (min-width: 901px) {
  .nav__links { display: flex; }
}

@media (max-width: 1024px) {
  .pipeline { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .cards--3 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .demo__stage { grid-template-columns: 300px minmax(0, 1fr); }
  .studio { grid-template-columns: 1fr; gap: 24px; }
  .logo-band { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .logo-band__item:nth-child(n + 4) { border-top: 1px solid var(--line); }
  .footer__grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 900px) {
  .nav__links {
    position: absolute;
    top: var(--nav-h); left: 0; right: 0;
    flex-direction: column;
    align-items: flex-start;
    gap: 0;
    padding: 8px 20px 20px;
    background: #fff;
    border-bottom: 1px solid var(--line);
    display: none;
  }
  .nav__links.is-open { display: flex; }
  .nav__links a { padding: 12px 0; font-size: 15px; }
  .nav__toggle { display: flex; }
  .nav__cta { display: none; }
  .brand__entity, .brand__divider { display: none; }
}

@media (max-width: 768px) {
  /* 移动端两个按钮仍并排，不占满宽 */
  .hero--centered .hero__actions { flex-direction: row; flex-wrap: wrap; gap: 16px; }
  .hero--centered .hero__actions .btn { width: auto; flex: 0 0 auto; padding: 0 20px; }

  .cards--3 { grid-template-columns: 1fr; }
  .pipeline { grid-template-columns: 1fr; }

  .bleed__caption { flex-direction: column; align-items: flex-start; gap: 12px; }
  .bleed__meta { display: none; }

  .demo__stage { grid-template-columns: 1fr; }
  .phone, .agent { min-height: 400px; }

  .demo__switch { display: grid; grid-template-columns: 1fr 1fr; }
  .demo__tab { padding: 11px 8px; }

  .scales { grid-template-columns: 1fr; }

  .logo-band { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .logo-band__item { padding-block: 22px; font-size: 14px; }
  .logo-band__item:nth-child(2n + 1) { border-left: 0; }
  .logo-band__item:nth-child(n + 3) { border-top: 1px solid var(--line); }

  .footer__grid { grid-template-columns: 1fr; gap: 32px; }
  .cta__actions { flex-direction: column; }
  .cta__actions .btn { width: 100%; }
}

/* ============================================================
   FDE 子页专属组件
   ============================================================ */

/* ---------- 五步方法（左右分栏列表） ---------- */
.steps-list {
  margin: clamp(40px, 5vw, 56px) 0 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--line);
}
.step-row {
  display: grid;
  grid-template-columns: 320px minmax(0, 1fr);
  gap: clamp(24px, 5vw, 72px);
  padding-block: 32px;
  border-bottom: 1px solid var(--line);
}
.step-row__head { display: flex; gap: 20px; align-items: baseline; }
.step-row__no {
  flex-shrink: 0;
  font-size: 12px; font-weight: 500;
  letter-spacing: 0.06em;
  color: var(--fg-44);
}
.step-row__title {
  font-size: clamp(1.25rem, 1.8vw, 1.5rem);
  font-weight: 500;
  letter-spacing: -0.02em;
  line-height: 1.25;
}
.step-row__title span {
  display: block;
  margin-top: 6px;
  font-size: 13px;
  font-weight: 500;
  letter-spacing: 0;
  color: var(--fg-44);
}
.step-row__body p {
  max-width: 620px;
  font-size: 15px; line-height: 1.8;
  color: var(--fg-60);
}
.step-row__out {
  margin-top: 16px;
  padding-top: 14px;
  border-top: 1px solid var(--line);
  font-size: 13px !important;
  color: var(--fg-44) !important;
}
.step-row__out strong { color: var(--fg); font-weight: 500; }

/* ---------- 边界清单 ---------- */
.bounds {
  margin-top: clamp(32px, 4vw, 48px);
  border-top: 1px solid var(--line);
}
.bounds__item {
  display: flex;
  gap: clamp(20px, 3vw, 40px);
  padding-block: 28px;
  border-bottom: 1px solid var(--line);
}
.bounds__mark {
  flex-shrink: 0;
  font-size: 12px; font-weight: 500;
  letter-spacing: 0.06em;
  color: var(--fg-44);
  padding-top: 4px;
}
.bounds__title {
  font-size: 17px; font-weight: 500;
  letter-spacing: -0.015em;
}
.bounds__body {
  margin-top: 8px;
  max-width: 560px;
  font-size: 14px; line-height: 1.7;
  color: var(--fg-60);
}

/* ---------- 合作方式三步 ---------- */
.engage {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: var(--grid-gap);
  margin-top: clamp(32px, 4vw, 48px);
}
.engage__item {
  padding: 28px 24px 32px;
  border-radius: var(--radius-md);
  background: var(--surface);
}
.engage__no {
  font-size: 12px; font-weight: 500;
  letter-spacing: 0.06em;
  color: var(--fg-44);
}
.engage__title {
  margin-top: 16px;
  font-size: 17px; font-weight: 500;
  letter-spacing: -0.015em;
}
.engage__body {
  margin-top: 12px;
  font-size: 14px; line-height: 1.7;
  color: var(--fg-60);
}

@media (max-width: 1024px) {
  .step-row { grid-template-columns: 1fr; gap: 16px; }
  .engage { grid-template-columns: 1fr; }
}

/* ============================================================
   首页 · 接入前后对比
   ============================================================ */
.gap { padding-top: clamp(56px, 6vw, 88px); }
.compare {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-top: clamp(36px, 4vw, 48px);
}
.compare__col {
  display: flex;
  flex-direction: column;
  padding: 32px 28px 26px;
  border-radius: var(--radius-md);
}
.compare__col--before { background: var(--surface); }
.compare__col--after { background: #0a0a0a; color: #fff; }

.compare__head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 16px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--line);
}
.compare__col--after .compare__head { border-bottom-color: rgba(255, 255, 255, 0.18); }
.compare__label {
  font-size: 13px; font-weight: 500;
  letter-spacing: 0.04em;
  color: var(--fg-60);
}
.compare__col--after .compare__label { color: rgba(255, 255, 255, 0.6); }
.compare__time {
  font-size: clamp(1.75rem, 2.6vw, 2.25rem);
  font-weight: 500;
  letter-spacing: -0.035em;
  line-height: 1;
  white-space: nowrap;
}
.compare__col--before .compare__time { color: var(--n-10); }
.compare__delta {
  margin-left: 10px;
  font-size: 13px; font-weight: 500;
  letter-spacing: 0;
  color: rgba(255, 255, 255, 0.55);
  vertical-align: middle;
}

.compare__steps { margin: 8px 0 0; padding: 0; list-style: none; }
.compare__steps li {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 16px;
  padding-block: 13px;
  font-size: 14px;
  border-bottom: 1px solid var(--line);
}
.compare__col--after .compare__steps li { border-bottom-color: rgba(255, 255, 255, 0.12); }
.compare__steps li:last-child { border-bottom: 0; }
.compare__step { line-height: 1.5; }
.compare__cost {
  flex-shrink: 0;
  font-size: 13px;
  text-align: right;
  color: var(--fg-44);
  white-space: nowrap;
}
.compare__col--before .compare__cost { color: var(--n-10); }
.compare__col--after .compare__cost { color: rgba(255, 255, 255, 0.62); }

.compare__foot {
  margin-top: auto;
  padding-top: 20px;
  font-size: 13px;
  color: var(--fg-60);
}
.compare__col--after .compare__foot { color: rgba(255, 255, 255, 0.55); }

.gap__note {
  margin-top: 20px;
  font-size: 12.5px;
  color: var(--fg-44);
}

@media (max-width: 768px) {
  .compare { grid-template-columns: 1fr; }
  .compare__col { padding: 24px 20px 20px; }
  .compare__cost { white-space: normal; }
}

/* ---------- 合作伙伴 logo（统一纯黑填充） ---------- */
.logo-band__img {
  height: 28px;
  width: auto;
  max-width: 160px;
  object-fit: contain;
}
/* 若谷云为方形竖版标识，单独放大以匹配横向字标的视觉重量 */
.logo-band__img[alt="若谷云"] { height: 46px; max-width: 60px; }
.logo-band__text {
  font-size: 16px;
  font-weight: 600;
  letter-spacing: 0.02em;
  color: var(--n-10);
}

@media (max-width: 768px) {
  .logo-band__img { height: 24px; max-width: 130px; }
  .logo-band__img[alt="若谷云"] { height: 38px; max-width: 50px; }
  .logo-band__text { font-size: 14px; }
}

/* ============================================================
   首页 · 立场：模型已智能，更要处理真实工作（左文右图）
   ============================================================ */
.thesis { padding-top: clamp(64px, 7vw, 112px); }
.thesis__grid {
  display: grid;
  grid-template-columns: minmax(0, 0.8fr) minmax(0, 1.2fr);
  gap: clamp(40px, 6vw, 88px);
  align-items: center;
}
.thesis__title { text-wrap: balance; }
.thesis__list {
  margin-top: clamp(20px, 2.4vw, 30px);
  padding-left: 20px;
  list-style: disc;
  display: grid;
  gap: 16px;
}
.thesis__list li {
  padding-left: 2px;
  font-size: var(--type-p1-size);   /* DNA 正文档：17px / 1.647 */
  line-height: 1.68;
  color: var(--fg);                 /* 正文用近黑，不用次级灰 */
}
.thesis__list li::marker { color: var(--fg); font-size: 0.82em; }
.thesis__list strong { color: var(--fg); font-weight: 600; }
.thesis__media { margin: 0; }

@media (max-width: 900px) {
  .thesis__grid { grid-template-columns: 1fr; gap: 28px; }
  .thesis__media { order: -1; }              /* 窄屏：图在文上方 */
  .thesis__title {
    font-size: clamp(1.15rem, 5.6vw, 1.5rem);  /* 收小以保证标题单行 */
    white-space: nowrap;
  }
}
@media (max-width: 768px) {
  .thesis { padding-top: 56px; }
}

/* ============================================================
   首页 · 以成果为起点，全力将其实现
   复刻 openai.com/zh-Hans-CN/business/forward-deployed-engineering/
   同名章节：居中标题 → 居中正文 → 胶囊按钮 → 四栏图标卡
   实测参照（1440）：H2 30/500/-0.3px；正文 17/400/28；按钮高 40；
   卡片 322×210.6（padding 24、1px 发丝线、radius 6.08、栏距 24）
   ============================================================ */
.outcome { padding-block: clamp(32px, 4vw, 56px); }
/* 上下各收一档：让本节的视觉留白由 160+160 降到 56+56 */
.thesis { padding-bottom: clamp(32px, 4vw, 56px); }
.outcome + .gap { padding-top: clamp(32px, 4vw, 56px); }
.outcome__head {
  max-width: 900px;
  margin-inline: auto;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
}
.outcome__title { text-wrap: balance; }
.outcome__lead {
  margin-top: 24px;
  text-wrap: balance;
  color: var(--fg);                 /* 原站正文为纯黑，不降级为次级灰 */
}
.outcome__actions { margin-top: 32px; display: flex; justify-content: center; }
.outcome__cards { margin-top: 24px; }
.outcome__card { gap: 20px; }
/* 原站卡片标题走 h4 字阶（22/500/-0.22），正文行高 1.64 —— 与站内卡片基线不同，单独对齐 */
.outcome__card .card__title {
  font-size: var(--type-h4-size);
  line-height: var(--type-h4-line);
  letter-spacing: var(--type-h4-track);
}
.outcome__card .card__body {
  color: var(--fg);
  line-height: var(--type-p2-line);
}
.outcome__icon {
  width: 24px; height: 24px;
  flex: none;
  color: var(--fg);
}

@media (max-width: 1024px) {
  .outcome__cards { margin-top: 20px; }
}
@media (max-width: 768px) {
  .outcome__lead { margin-top: 20px; }
  .outcome__actions { margin-top: 24px; }
}

/* ============================================================
   首页 · 与 OpenAI 一起开发并交付（起）→ 选定工作流程（止）
   复刻 openai.com/zh-Hans-CN/business/forward-deployed-engineering/
   实测参照（1440，内宽 1376）：
   · 组间 64；组内 标题→内容 24；H2 30/500/-0.3；正文 17/400/28
   · 流程：列表 326 + 媒体 1026（gap 24），媒体 1026×577
   · 客户卡：#f5f5f5(=rgba(0,0,0,.04))、radius 6.08、padding 32，4 列 gap 16，主卡 2×2
   · 平台卡：1px 发丝线、radius 6.08、padding 24、4 列 gap 24
   · FAQ：列宽 676 居中；问 17/400 padding 16；答 14/400 rgba(0,0,0,.6)
   · 收尾面板：bg rgba(0,0,0,.04)、radius 6.08、padding 120；H2 48/500
   ============================================================ */
.ship { padding-block: clamp(32px, 4vw, 56px) 0; }
/* 紧接「以成果为起点」之后：两节留白合并为原站的 64 */
.outcome + .ship { padding-top: 8px; }
.ship-block + .ship-block { margin-top: clamp(40px, 4.5vw, 64px); }
/* 锚点落在无内边距的块上，跳转时让开 64 的粘性导航 */
.ship-block[id],
.path[id] { scroll-margin-top: calc(var(--nav-h) + 16px); }

.ship-head {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
}
.ship-head__title { text-wrap: balance; }
.ship-head__lead {
  margin-top: 24px;
  max-width: 900px;
  color: var(--fg);
  text-wrap: pretty;
}
.ship-head__actions { margin-top: 32px; }
.ship-head + * { margin-top: 24px; }

/* ---------- 5.1 五步流程 ---------- */
.phases {
  display: grid;
  grid-template-columns: 326px minmax(0, 1fr);
  gap: 24px;
  align-items: start;
}
.phases__list { min-width: 0; }
.phase { border-bottom: 1px solid var(--line); }
.phase__head {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 16px 0;
  cursor: pointer;
  list-style: none;
}
.phase__head::-webkit-details-marker { display: none; }
.phase__title {
  font-size: var(--type-p2-size);
  font-weight: 400;
  line-height: var(--type-p2-line);
  letter-spacing: -0.01em;
  color: var(--fg);
}
.phase[open] .phase__title {
  font-size: var(--type-h4-size);
  font-weight: 500;
  line-height: var(--type-h4-line);
  letter-spacing: var(--type-h4-track);
}
.phase__body { padding-bottom: 24px; }
.phase__body p {
  font-size: var(--type-p2-size);
  line-height: var(--type-p2-line);
  letter-spacing: -0.01em;
  color: var(--fg-60);
}

.phases__stage {
  position: relative;
  min-width: 0;
  aspect-ratio: 1026 / 577;
  border-radius: var(--radius-md);
  overflow: hidden;
}
.stage {
  position: absolute;
  inset: 0;
  margin: 0;
  border-radius: var(--radius-md);
  overflow: hidden;
  background:
    radial-gradient(120% 90% at 18% 12%, rgba(255, 255, 255, 0.85) 0%, rgba(255, 255, 255, 0) 60%),
    linear-gradient(104deg, #eef5fd 0%, #e4f0fb 46%, #d7e9f7 100%);
}
.stage img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

/* ---------- 5.2 合作客户 ---------- */
.proof {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 16px;
}
.proof__card {
  display: flex;
  flex-direction: column;
  min-height: 288px;
  padding: 32px;
  background: var(--surface);
  border-radius: var(--radius-md);
}
.proof__card--lead { grid-column: span 2; grid-row: span 2; min-height: 592px; }
.proof__logo {
  margin: 0;
  min-height: 32px;
  display: flex;
  align-items: center;
  font-size: 17px;
  font-weight: 600;
  letter-spacing: 0.04em;
  color: var(--fg);
}
.proof__logo img { display: block; width: auto; height: 32px; }
.proof__logo span { margin-left: 8px; }
.proof__logo--text { font-size: 20px; letter-spacing: 0.02em; }
.proof__quote {
  margin: auto 0 0;
  font-size: var(--type-h3-size);
  font-weight: 500;
  line-height: 1.32;
  letter-spacing: -0.01em;
}
.proof__who {
  margin-top: 16px;
  font-size: var(--type-p2-size);
  font-weight: 500;
  line-height: var(--type-p2-line);
}
.proof__stat { margin-top: 0; }
.proof__num {
  display: flex;
  align-items: baseline;
  gap: 6px;
  margin-top: 28px;
  font-size: var(--type-h2-5-size);
  font-weight: 700;
  line-height: 1.1;
  letter-spacing: -0.02em;
  font-variant-numeric: tabular-nums;
}
.proof__num-unit {
  font-size: 0.9375rem;
  font-weight: 500;
  letter-spacing: 0;
  color: var(--fg-60);
}
.proof__desc {
  margin-top: 6px;
  font-size: 1.25rem;
  line-height: 1.3;
  letter-spacing: -0.01em;
  color: var(--fg-60);
}
.proof__more {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  margin-top: auto;
  padding-top: 16px;
  font-size: var(--type-p2-size);
  font-weight: 500;
  color: var(--fg);
}
.proof__more:hover { text-decoration: underline; text-underline-offset: 3px; }

/* ---------- 5.3 平台支撑 ---------- */
.platform {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 24px;
}
.platform__card {
  min-height: 212px;
  padding: 24px;
  border: 1px solid var(--line);
  border-radius: var(--radius-md);
}
.platform__title {
  font-size: var(--type-h4-size);
  font-weight: 500;
  line-height: var(--type-h4-line);
  letter-spacing: var(--type-h4-track);
}
.platform__body {
  margin-top: 16px;
  font-size: var(--type-p2-size);
  line-height: var(--type-p2-line);
  letter-spacing: -0.01em;
  color: var(--fg);
}
.platform__body a { text-decoration: underline; text-underline-offset: 2px; }

/* ---------- 5.4 精选资源 + 探索更多 ---------- */
.featured {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 24px;
  align-items: center;
  max-width: 948px;
  margin-inline: auto;
}
.featured__media {
  aspect-ratio: 1;
  border-radius: var(--radius-md);
  overflow: hidden;
  background: #f5f5f5;
}
.featured__media img {
  width: 100%; height: 100%;
  object-fit: cover;
  display: block;
}
.featured__label { font-size: var(--type-p2-size); }
.featured__title { margin-top: 16px; text-wrap: balance; }
.featured__more {
  display: inline-block;
  margin-top: 24px;
  font-size: var(--type-p1-size);
  letter-spacing: -0.01em;
  border-bottom: 1px solid var(--fg);
  padding-bottom: 2px;
}
.featured__more:hover { border-bottom-color: transparent; }

.explore {
  column-count: 2;
  column-gap: 24px;
  max-width: 1143px;
  margin-inline: auto;
}
.explore__item {
  display: flex;
  align-items: center;
  min-height: 120px;
  margin-bottom: 28px;
  break-inside: avoid;
  color: var(--fg);
}
.explore__thumb {
  flex: 0 0 120px;
  height: 120px;
  border-radius: var(--radius-md);
  background: linear-gradient(145deg, #f2f3f5 0%, #e4e7ea 100%);
}
.explore__text {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding-left: 32px;
}
.explore__title {
  font-size: 1.125rem;
  font-weight: 500;
  line-height: 1.32;
  letter-spacing: -0.01em;
}
.explore__ext { margin-left: 4px; font-size: 0.9em; }
.explore__src {
  font-size: var(--type-p2-size);
  font-weight: 500;
  color: var(--fg);
}
.explore__item:hover .explore__title { text-decoration: underline; text-underline-offset: 3px; }

/* ---------- 5.5 常见问题 ---------- */
.faq {
  width: 100%;
  max-width: 676px;
  margin-inline: auto;
  border-top: 1px solid var(--line);
}
.faq__item { border-bottom: 1px solid var(--line); }
.faq__q {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 16px 0;
  font-size: var(--type-p1-size);
  line-height: var(--type-p1-line);
  letter-spacing: -0.01em;
  color: var(--fg);
  cursor: pointer;
  list-style: none;
}
.faq__q::-webkit-details-marker { display: none; }
.faq__q::after {
  content: "+";
  font-size: 20px;
  font-weight: 300;
  line-height: 1;
  color: var(--fg);
}
.faq__item[open] .faq__q::after { content: "\2212"; }
.faq__a { padding-bottom: 24px; }
.faq__a p {
  font-size: var(--type-p2-size);
  line-height: var(--type-p2-line);
  letter-spacing: -0.01em;
  color: var(--fg-60);
}
.faq__a p + p { margin-top: 16px; }
.faq__a b { font-weight: 600; }
.faq__a a { text-decoration: underline; text-underline-offset: 2px; }

/* ---------- 5.6 选定工作流程 ---------- */
.path {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  padding: 120px 32px;
  background: var(--surface);
  border-radius: var(--radius-md);
}
.path__title { text-wrap: balance; }
.path__sub { margin-top: 12px; font-size: var(--type-p1-size); }
.path__actions { margin-top: 32px; }

@media (max-width: 1024px) {
  .phases { grid-template-columns: 1fr; }
  .phases__stage { aspect-ratio: 16 / 9; }
  .proof { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .proof__card--lead { grid-column: span 2; grid-row: auto; min-height: 0; }
  .proof__card--lead .proof__num { margin-top: 40px; }
  .platform { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .explore { column-count: 1; }
}

@media (max-width: 768px) {
  .ship-block + .ship-block { margin-top: 48px; }
  .proof { grid-template-columns: minmax(0, 1fr); }
  .proof__card--lead { grid-column: auto; grid-row: auto; }
  .proof__card { min-height: 0; }
  .proof__num { font-size: 2rem; }
  .proof__desc { font-size: 1.0625rem; }
  .proof__card--lead .proof__quote { font-size: 1.5rem; }
  .platform { grid-template-columns: 1fr; }
  .featured { grid-template-columns: 1fr; }
  .explore__thumb { flex: 0 0 88px; height: 88px; }
  .explore__text { padding-left: 20px; }
  .path { padding: 64px 24px; }
}

/* ---------- 13. 文章区（长文页 + 列表页，复用 dna 的 .article / .toc / .prose） ---------- */
.post { min-width: 0; }
.post__head { margin-bottom: 40px; }
.post__head .overline { display: block; }
.post__title { margin-top: 12px; text-wrap: balance; }

.toc__title { margin-bottom: 10px; font-size: 13px; font-weight: 500; color: var(--fg); }
.toc__back {
  display: block;
  margin-top: 20px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  color: var(--fg-44);
}
.toc__back:hover { color: var(--fg); }

/* 目录锚点跳转时，标题不要被 64px 吸顶导航盖住 */
.prose [id] { scroll-margin-top: calc(var(--nav-h) + 16px); }
.prose h2 {
  font-size: var(--type-h3-size);
  line-height: var(--type-h3-line);
  letter-spacing: var(--type-h3-track);
  font-weight: 500;
}
.prose h3,
.prose h4 {
  margin-top: 1.8em;
  margin-bottom: 0.4em;
  font-size: var(--type-h4-size);
  line-height: var(--type-h4-line);
  letter-spacing: var(--type-h4-track);
  font-weight: 500;
}
.prose strong { font-weight: 500; color: var(--fg); }
.prose a { text-decoration: underline; text-underline-offset: 2px; }
.prose a:hover { color: var(--fg-60); }
.prose ul,
.prose ol { margin-block: 1.2em; padding-left: 1.4em; }
.prose ul { list-style: disc; }
.prose ol { list-style: decimal; }
.prose li + li { margin-top: 0.5em; }
.prose code {
  padding: 0.1em 0.35em;
  font-family: var(--font-mono);
  font-size: 0.92em;
  background: var(--n-5);
  border-radius: var(--radius-xs);
}
.prose blockquote {
  margin: 1.6em 0;
  padding-left: 16px;
  border-left: 2px solid var(--line);
  color: var(--fg-60);
  font-weight: inherit;
}

.posts { margin-top: 48px; border-top: 1px solid var(--line); }
.posts__item { padding-block: 28px; border-bottom: 1px solid var(--line); }
.posts__date { display: block; color: var(--fg-44); font-size: var(--type-meta-size); line-height: var(--type-meta-line); }
.posts__title {
  margin-top: 8px;
  font-size: var(--type-h4-size);
  line-height: var(--type-h4-line);
  letter-spacing: -0.015em;
  font-weight: 500;
  text-wrap: balance;
}
.posts__title a:hover { color: var(--fg-60); }
.posts__excerpt {
  margin-top: 8px;
  max-width: var(--measure);
  color: var(--fg-60);
  font-size: var(--type-p2-size);
  line-height: var(--type-p2-line);
}

/* 移动端：dna 的 .toc 在 ≤1024 变横向 flex，标题与返回链接需各占一行 */
@media (max-width: 1024px) {
  .toc__title { flex: 1 1 100%; margin-bottom: 4px; }
  .toc__back { flex: 1 1 100%; margin-top: 12px; padding-top: 12px; }
}