/* ==========================================================================
   传乘AI官网 - style.css
   设计基准：Zendesk 大留白/大标题/短句排版语言（PRD 第2节视觉规范）
   移动优先：基础样式=375px基准，768px/1200px 断点向上增强
   ========================================================================== */

:root {
  --color-primary: #0F2B46;
  --color-accent: #E8590C;
  --color-bg: #FFFFFF;
  --color-bg-alt: #F6F8FA;
  --color-text: #3A4A5A;
  --color-text-muted: #8296A6;
  --color-white: #FFFFFF;

  --font-sans: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", "Noto Sans SC", sans-serif;

  --radius-card: 12px;
  --radius-btn: 8px;
  --shadow-card: 0 4px 24px rgba(15, 43, 70, 0.08);
  --shadow-card-hover: 0 10px 32px rgba(15, 43, 70, 0.14);

  --section-space: 56px;
  --header-height: 64px;

  --max-width: 1200px;
}

@media (min-width: 768px) {
  :root {
    --section-space: 96px;
    --header-height: 72px;
  }
}

/* ---------- Reset ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}
img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }
ul, ol { list-style: none; margin: 0; padding: 0; }
button { font: inherit; color: inherit; background: none; border: none; cursor: pointer; padding: 0; }
h1, h2, h3, p { margin: 0; }

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
}

@media (min-width: 768px) {
  .container { padding: 0 40px; }
}

/* ---------- Typography ---------- */
.section-title {
  font-size: 26px;
  font-weight: 700;
  color: var(--color-primary);
  text-align: center;
  letter-spacing: -0.01em;
}
.section-title--light { color: var(--color-white); }

.section-subtitle {
  margin-top: 12px;
  font-size: 16px;
  color: var(--color-text-muted);
  text-align: center;
}

@media (min-width: 768px) {
  .section-title { font-size: 36px; }
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 24px;
  border-radius: var(--radius-btn);
  font-size: 15px;
  font-weight: 600;
  transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;
  white-space: nowrap;
}
.btn--primary {
  background: var(--color-accent);
  color: var(--color-white);
}
.btn--primary:hover {
  background: #cf4e0a;
  box-shadow: 0 6px 18px rgba(232, 89, 12, 0.28);
}
.btn--outline {
  background: transparent;
  color: var(--color-primary);
  border: 1.5px solid var(--color-primary);
}
.btn--outline:hover {
  background: var(--color-primary);
  color: var(--color-white);
}
.btn--lg { padding: 14px 28px; font-size: 16px; }

/* ---------- Reveal-on-scroll (progressive enhancement) ---------- */
.js .reveal {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 0.3s ease-out, transform 0.3s ease-out;
}
.js .reveal.is-visible {
  opacity: 1;
  transform: translateY(0);
}

/* ---------- Placeholder boxes (images) ---------- */
.placeholder-box {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 8px;
  text-align: center;
  background: var(--color-bg-alt);
  border: 2px dashed #C7D2DC;
  border-radius: var(--radius-card);
  color: var(--color-text-muted);
  font-size: 14px;
  padding: 24px;
}
.placeholder-box__name {
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-weight: 700;
  color: var(--color-primary);
  background: rgba(232, 89, 12, 0.1);
  padding: 2px 10px;
  border-radius: 999px;
}
.placeholder-box--qr { width: 160px; height: 160px; margin: 0 auto; }
.qr-image {
  width: 160px;
  height: 160px;
  margin: 0 auto;
  border-radius: var(--radius-card);
  box-shadow: var(--shadow-card);
}

.placeholder-text {
  color: var(--color-accent);
  border: 1px dashed var(--color-accent);
  border-radius: 6px;
  padding: 2px 10px;
  font-weight: 600;
}

/* ==========================================================================
   S0 顶部导航
   ========================================================================== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--color-white);
  border-bottom: 1px solid transparent;
  transition: box-shadow 0.2s ease, border-color 0.2s ease;
}
.site-header.is-scrolled {
  box-shadow: 0 2px 12px rgba(15, 43, 70, 0.08);
  border-bottom-color: #EDF1F5;
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--header-height);
}

.nav__brand {
  font-size: 20px;
  font-weight: 800;
  color: var(--color-primary);
  letter-spacing: -0.01em;
}

.nav__menu {
  display: none;
  align-items: center;
  gap: 32px;
  font-size: 15px;
  font-weight: 500;
  color: var(--color-primary);
}
.nav__menu a { opacity: 0.85; transition: opacity 0.2s ease; }
.nav__menu a:hover { opacity: 1; }

.nav__cta { display: none; }

.nav__toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  color: var(--color-primary);
}
.nav__toggle svg { width: 24px; height: 24px; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; }

.nav__drawer {
  position: fixed;
  inset: 0;
  z-index: 200;
  background: var(--color-white);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 28px;
  font-size: 22px;
  font-weight: 600;
  color: var(--color-primary);
  transform: translateX(100%);
  transition: transform 0.3s ease;
}
.nav__drawer.is-open { transform: translateX(0); }
.nav__drawer-close {
  position: absolute;
  top: 20px;
  right: 20px;
  width: 40px;
  height: 40px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}
.nav__drawer-close svg { width: 24px; height: 24px; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; }

@media (min-width: 768px) {
  .nav__menu { display: flex; }
  .nav__cta { display: inline-flex; }
  .nav__toggle { display: none; }
}

/* ==========================================================================
   S1 Hero
   ========================================================================== */
.hero {
  padding: 48px 0 var(--section-space);
  background: var(--color-white);
}
.hero__inner {
  display: flex;
  flex-direction: column;
  gap: 40px;
}
.hero__copy { max-width: 640px; }

.pill {
  display: inline-block;
  padding: 6px 16px;
  border-radius: 999px;
  background: #E7F0F8;
  color: var(--color-primary);
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 20px;
}

.hero__title {
  font-size: 32px;
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1.25;
  letter-spacing: -0.02em;
}

.hero__subtitle {
  margin-top: 20px;
  font-size: 17px;
  color: var(--color-text);
}

.hero__actions {
  margin-top: 32px;
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
}

.hero__note {
  margin-top: 20px;
  font-size: 14px;
  color: var(--color-text-muted);
}

.hero__visual { flex: none; }
.hero__image {
  width: 100%;
  height: auto;
  display: block;
}

@media (min-width: 768px) {
  .hero__title { font-size: 48px; }
}
@media (min-width: 1200px) {
  .hero { padding-top: 64px; }
  .hero__inner { flex-direction: row; align-items: center; }
  .hero__copy { flex: 0 0 56%; }
  .hero__visual { flex: 0 0 40%; }
  .hero__title { font-size: 56px; }
}

/* ==========================================================================
   S2 信任条
   ========================================================================== */
.trust {
  padding: 40px 0;
  background: var(--color-bg-alt);
  text-align: center;
}
.trust__label {
  font-size: 14px;
  color: var(--color-text-muted);
  font-weight: 600;
}
.trust__industries {
  margin-top: 12px;
  font-size: 15px;
  color: var(--color-text-muted);
  line-height: 1.9;
}

.stat-grid {
  margin-top: 32px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
}
.stat-card { padding: 8px; }
.stat-number {
  font-size: 32px;
  font-weight: 800;
  color: var(--color-primary);
}
.stat-number--accent { color: var(--color-accent); }
.stat-card__label {
  margin-top: 4px;
  font-size: 13px;
  color: var(--color-text-muted);
}

.trust__footnote {
  margin-top: 20px;
  font-size: 12px;
  color: var(--color-text-muted);
}

@media (min-width: 768px) {
  .stat-number { font-size: 44px; }
  .stat-card__label { font-size: 15px; }
}

/* ==========================================================================
   S3 三大核心服务
   ========================================================================== */
.services { padding: var(--section-space) 0; }

.card-grid {
  margin-top: 48px;
  display: grid;
  grid-template-columns: 1fr;
  gap: 24px;
}

.card {
  background: var(--color-white);
  border-radius: var(--radius-card);
  box-shadow: var(--shadow-card);
  padding: 32px;
  transition: transform 0.25s ease, box-shadow 0.25s ease;
}
.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-card-hover);
}

.card__icon {
  display: inline-flex;
  width: 48px;
  height: 48px;
  align-items: center;
  justify-content: center;
  border-radius: 12px;
  background: #E7F0F8;
  color: var(--color-primary);
  margin-bottom: 20px;
}
.card__icon svg { width: 24px; height: 24px; fill: none; stroke: currentColor; stroke-width: 1.6; stroke-linecap: round; stroke-linejoin: round; }

.card__title {
  font-size: 19px;
  font-weight: 700;
  color: var(--color-primary);
}
.card__body {
  margin-top: 12px;
  font-size: 15px;
  color: var(--color-text);
}
.card__link {
  display: inline-block;
  margin-top: 20px;
  font-size: 14px;
  font-weight: 600;
  color: var(--color-accent);
}

@media (min-width: 768px) {
  .card-grid { grid-template-columns: repeat(3, 1fr); gap: 32px; }
}

/* ==========================================================================
   S4 四步落地
   ========================================================================== */
.process {
  padding: var(--section-space) 0;
  background: var(--color-bg-alt);
}

.timeline {
  margin-top: 48px;
  display: grid;
  grid-template-columns: 1fr;
  gap: 32px;
}

.timeline__item {
  position: relative;
  padding-left: 24px;
  border-left: 2px solid #D7E0E8;
}
.timeline__index {
  font-size: 13px;
  font-weight: 800;
  color: var(--color-accent);
  letter-spacing: 0.04em;
}
.timeline__title {
  margin-top: 6px;
  font-size: 18px;
  font-weight: 700;
  color: var(--color-primary);
}
.timeline__phase {
  display: inline-block;
  margin-top: 6px;
  font-size: 13px;
  color: var(--color-text-muted);
  font-weight: 600;
}
.timeline__body {
  margin-top: 10px;
  font-size: 15px;
  color: var(--color-text);
}

.process__closing {
  margin-top: 56px;
  text-align: center;
  font-size: 18px;
  font-weight: 700;
  color: var(--color-primary);
}

@media (min-width: 768px) {
  .timeline { grid-template-columns: repeat(4, 1fr); gap: 24px; }
  .timeline__item { border-left: none; border-top: 3px solid #D7E0E8; padding-left: 0; padding-top: 20px; }
}

/* ==========================================================================
   S5 为什么选传乘AI
   ========================================================================== */
.why { padding: var(--section-space) 0; }

.col-grid {
  margin-top: 48px;
  display: grid;
  grid-template-columns: 1fr;
  gap: 40px;
  text-align: center;
}

.col-item__icon {
  display: inline-flex;
  width: 56px;
  height: 56px;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  background: #FDEDE3;
  color: var(--color-accent);
  margin-bottom: 20px;
}
.col-item__icon svg { width: 26px; height: 26px; fill: none; stroke: currentColor; stroke-width: 1.6; stroke-linecap: round; stroke-linejoin: round; }

.col-item__title {
  font-size: 19px;
  font-weight: 700;
  color: var(--color-primary);
}
.col-item__body {
  margin-top: 12px;
  font-size: 15px;
  color: var(--color-text);
}

@media (min-width: 768px) {
  .col-grid { grid-template-columns: repeat(3, 1fr); }
}

/* ==========================================================================
   S6 服务成果
   ========================================================================== */
.results {
  padding: var(--section-space) 0;
  background: var(--color-primary);
  text-align: center;
}

.stat-grid--dark { grid-template-columns: repeat(2, 1fr); max-width: 560px; margin-left: auto; margin-right: auto; }
.stat-card--dark .stat-card__label { color: #C3D0DC; }

.results__footnote {
  margin-top: 24px;
  font-size: 12px;
  color: #9FB0C0;
  max-width: 640px;
  margin-left: auto;
  margin-right: auto;
}

.testimonial {
  margin: 40px auto 0;
  max-width: 560px;
  background: var(--color-white);
  border-radius: var(--radius-card);
  padding: 32px;
  text-align: left;
}
.testimonial__quote { font-size: 17px; color: var(--color-primary); font-style: normal; }
.testimonial__source { margin-top: 12px; font-size: 14px; color: var(--color-text-muted); }

/* ==========================================================================
   S7 我们不做什么
   ========================================================================== */
.boundaries { padding: var(--section-space) 0; }

.boundaries__list {
  margin-top: 40px;
  display: grid;
  grid-template-columns: 1fr;
  gap: 20px;
}
.boundaries__list li {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 16px;
  font-weight: 600;
  color: var(--color-primary);
  padding: 16px 20px;
  background: var(--color-bg-alt);
  border-radius: var(--radius-card);
}
.boundaries__icon {
  flex: none;
  width: 20px;
  height: 20px;
  color: var(--color-accent);
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
}

.boundaries__closing {
  margin-top: 32px;
  text-align: center;
  font-size: 14px;
  font-weight: 600;
  color: var(--color-accent);
}

@media (min-width: 768px) {
  .boundaries__list { grid-template-columns: repeat(2, 1fr); }
}

/* ==========================================================================
   S8 先修课入口
   ========================================================================== */
.precourse {
  padding: 32px 0;
  background: var(--color-bg-alt);
  border-top: 1px solid #E9EEF2;
  border-bottom: 1px solid #E9EEF2;
}
.precourse__inner {
  display: flex;
  flex-direction: column;
  gap: 20px;
  align-items: flex-start;
}
.precourse__text {
  font-size: 15px;
  color: var(--color-text);
  flex: 1;
}

@media (min-width: 768px) {
  .precourse__inner { flex-direction: row; align-items: center; justify-content: space-between; gap: 32px; }
}

/* ==========================================================================
   S9 关于传乘AI
   ========================================================================== */
.about { padding: var(--section-space) 0; }
.about__body {
  margin: 32px auto 0;
  max-width: 780px;
  font-size: 16px;
  color: var(--color-text);
  text-align: center;
}

/* ==========================================================================
   S10 常见问题
   ========================================================================== */
.faq {
  padding: var(--section-space) 0;
  background: var(--color-bg-alt);
}

.faq-list {
  margin-top: 40px;
  max-width: 780px;
  margin-left: auto;
  margin-right: auto;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.faq-item {
  background: var(--color-white);
  border-radius: var(--radius-card);
  box-shadow: var(--shadow-card);
  overflow: hidden;
}

.faq-question {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 20px 24px;
  font-size: 16px;
  font-weight: 700;
  color: var(--color-primary);
  text-align: left;
}

.faq-icon {
  flex: none;
  width: 20px;
  height: 20px;
  color: var(--color-accent);
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  transition: transform 0.25s ease;
}
.faq-question[aria-expanded="true"] .faq-icon { transform: rotate(45deg); }

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease;
}
.faq-answer p {
  padding: 0 24px 20px;
  font-size: 15px;
  color: var(--color-text);
}
.faq-item.is-open .faq-answer { max-height: 400px; }

/* ==========================================================================
   S11 联系我们
   ========================================================================== */
.contact { padding: var(--section-space) 0; text-align: center; }

.contact-grid {
  margin-top: 48px;
  display: grid;
  grid-template-columns: 1fr;
  gap: 40px;
}

.contact-item__caption {
  margin-top: 16px;
  font-size: 14px;
  color: var(--color-text-muted);
}
.contact-item__phone {
  display: inline-block;
  font-size: 28px;
  font-weight: 800;
  color: var(--color-primary);
}

@media (min-width: 768px) {
  .contact-grid { grid-template-columns: repeat(3, 1fr); }
}

/* ==========================================================================
   Footer
   ========================================================================== */
.site-footer {
  background: var(--color-primary);
  padding: 48px 0;
}
.site-footer__inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 24px;
  text-align: center;
}
.site-footer__brand {
  font-size: 16px;
  font-weight: 700;
  color: var(--color-white);
}
.site-footer__links {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 24px;
  font-size: 14px;
  color: #C3D0DC;
}
.site-footer__links a:hover { color: var(--color-white); }
.site-footer__meta {
  font-size: 12px;
  color: #8296A6;
}
.site-footer__meta a { text-decoration: none; }
.site-footer__meta a:hover { color: var(--color-white); text-decoration: underline; }
.site-footer__meta .placeholder-text {
  color: #F0AD82;
  border-color: #F0AD82;
}

@media (min-width: 768px) {
  .site-footer__inner { flex-direction: row; justify-content: space-between; text-align: left; }
}