/* ===== 司南 AI 教学助手 官网样式 ===== */
:root {
  --blue-900: #16335F;
  --blue-700: #1F4E9C;
  --blue-500: #2E6BC4;
  --blue-100: #E8F0FB;
  --orange-500: #E85D2A;
  --ink: #1F2937;
  --ink-light: #6B7280;
  --bg-warm: #FAF8F5;
  --border: #E5E7EB;
  --white: #FFFFFF;
  --radius: 10px;
  --shadow: 0 4px 16px rgba(31, 78, 156, 0.08);
  --shadow-hover: 0 10px 28px rgba(31, 78, 156, 0.16);
  --maxw: 1120px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", sans-serif;
  color: var(--ink);
  background: var(--white);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--blue-500); text-decoration: none; }
a:hover { text-decoration: underline; }

.container { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }

/* ===== 导航栏 ===== */
.nav {
  position: sticky; top: 0; z-index: 100;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.nav-inner {
  max-width: var(--maxw); margin: 0 auto; padding: 0 24px;
  height: 64px; display: flex; align-items: center; justify-content: space-between;
}
.nav-logo { display: flex; align-items: center; gap: 10px; font-weight: 600; color: var(--ink); font-size: 17px; }
.nav-logo img { height: 30px; width: auto; }
.nav-links { display: flex; align-items: center; gap: 22px; font-size: 14.5px; }
.nav-links a { color: var(--ink-light); transition: color 0.15s; white-space: nowrap; }
.nav-links a:hover { color: var(--blue-700); text-decoration: none; }
.nav-cta {
  background: var(--blue-700); color: #fff !important;
  padding: 8px 18px; border-radius: 8px; font-size: 14px;
  transition: background 0.15s;
}
.nav-cta:hover { background: var(--blue-900); text-decoration: none; }
.lang-switch {
  background: none; border: 1px solid var(--border); border-radius: 8px;
  padding: 6px 12px; font-size: 13.5px; font-weight: 600; color: var(--ink);
  cursor: pointer; font-family: inherit; line-height: 1.2;
  transition: border-color 0.15s, color 0.15s, background 0.15s;
}
.lang-switch:hover { border-color: var(--blue-500); color: var(--blue-700); background: var(--blue-100); }

/* ===== Hero ===== */
.hero {
  background: linear-gradient(160deg, #16335F 0%, #1F4E9C 55%, #2E6BC4 100%);
  color: #fff; padding: 96px 0 84px; overflow: hidden;
}
.hero-grid {
  max-width: var(--maxw); margin: 0 auto; padding: 0 24px;
  display: grid; grid-template-columns: 1.15fr 0.85fr; gap: 56px; align-items: center;
}
.hero-badge {
  display: inline-block; background: rgba(255,255,255,0.14); border: 1px solid rgba(255,255,255,0.25);
  padding: 5px 14px; border-radius: 999px; font-size: 13px; margin-bottom: 22px; letter-spacing: 0.5px;
}
.hero h1 { font-size: 42px; line-height: 1.3; font-weight: 700; margin-bottom: 20px; letter-spacing: 0.5px; }
.hero p.lead { font-size: 17px; color: rgba(255,255,255,0.85); max-width: 540px; margin-bottom: 36px; }
.hero-ctas { display: flex; gap: 14px; flex-wrap: wrap; }
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 13px 28px; border-radius: 10px; font-size: 15px; font-weight: 600;
  transition: transform 0.15s, box-shadow 0.15s, background 0.15s;
  cursor: pointer; border: none;
}
.btn-primary { background: #fff; color: var(--blue-900); }
.btn-primary:hover { background: var(--blue-100); transform: translateY(-2px); box-shadow: 0 8px 20px rgba(0,0,0,0.18); text-decoration: none; }
.btn-ghost { background: rgba(255,255,255,0.12); color: #fff; border: 1px solid rgba(255,255,255,0.35); }
.btn-ghost:hover { background: rgba(255,255,255,0.2); transform: translateY(-2px); text-decoration: none; }
.hero-visual {
  background: rgba(255,255,255,0.06); border: 1px solid rgba(255,255,255,0.14);
  border-radius: 16px; padding: 28px; backdrop-filter: blur(6px);
}
.hero-visual img { width: 100%; height: auto; display: block; border-radius: 8px; }
.hero-stats { display: flex; gap: 36px; margin-top: 44px; }
.hero-stat b { font-size: 26px; display: block; font-weight: 700; }
.hero-stat span { font-size: 13px; color: rgba(255,255,255,0.75); }

/* ===== 功能 ===== */
.section { padding: 88px 0; }
.section-alt { background: var(--bg-warm); }
.section-head { text-align: center; max-width: 640px; margin: 0 auto 56px; }
.section-head h2 { font-size: 30px; font-weight: 700; color: var(--blue-900); margin-bottom: 14px; }
.section-head p { color: var(--ink-light); font-size: 16px; }

.cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.card {
  background: var(--white); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 32px 28px; transition: transform 0.18s, box-shadow 0.18s;
}
.card:hover { transform: translateY(-4px); box-shadow: var(--shadow-hover); }
.card-icon {
  width: 48px; height: 48px; border-radius: 12px; display: flex; align-items: center; justify-content: center;
  font-size: 24px; margin-bottom: 18px;
}
.card-icon.b1 { background: var(--blue-100); }
.card-icon.b2 { background: #FDEBE3; }
.card-icon.b3 { background: #E8F6EF; }
.card h3 { font-size: 18px; margin-bottom: 10px; color: var(--blue-900); }
.card p { font-size: 14.5px; color: var(--ink-light); }

/* ===== 功能块（四大块）===== */
.feature-row {
  display: grid; grid-template-columns: 1fr 1.1fr; gap: 56px; align-items: center;
  margin-top: 12px;
}
.feature-copy { min-width: 0; }
.feature-title { font-size: 18px; color: var(--blue-900); margin: 22px 0 8px; }
.feature-copy > .feature-title:first-child { margin-top: 0; }
.feature-copy p { font-size: 15px; color: var(--ink-light); }

/* 教案生成：轮播 + 步骤条 */
.plan-layout { margin-top: 8px; }
/* 轮播宽度收敛：全宽 1072px 过大(占视口近半高)，居中 860px 保证图片完整可见且滑动有边界参照 */
.plan-carousel-wrap { max-width: 860px; margin: 0 auto; }
.plan-steps {
  display: flex; gap: 10px; margin-top: 20px;
  flex-wrap: wrap; justify-content: center;
}
.plan-step {
  display: flex; align-items: center; gap: 8px;
  min-height: 48px; padding: 6px 16px 6px 10px; border-radius: 999px;
  border: 1px solid var(--border); background: var(--white);
  cursor: pointer; transition: border-color 0.15s, background 0.15s, box-shadow 0.15s;
  font-size: 13.5px; color: var(--ink); font-family: inherit;
  line-height: 1.3;
}
.plan-step .step-name { display: flex; flex-direction: column; justify-content: center; text-align: left; }
.plan-step .step-num {
  width: 24px; height: 24px; font-size: 12.5px; margin-top: 0;
  flex: 0 0 auto;
}
.plan-step:hover { border-color: var(--blue-500); }
.plan-step.active {
  background: var(--blue-700); border-color: var(--blue-700); color: #fff;
}
.plan-step.active .step-num { background: rgba(255,255,255,0.22); color: #fff; }
.plan-step .step-name { line-height: 1.35; }

/* 教案步骤列表 */
.step-list { list-style: none; display: flex; flex-direction: column; gap: 16px; }
.step-list li { display: flex; gap: 14px; align-items: flex-start; }
.step-num {
  flex: 0 0 auto; width: 30px; height: 30px; border-radius: 50%;
  background: var(--blue-100); color: var(--blue-700);
  display: flex; align-items: center; justify-content: center;
  font-size: 14px; font-weight: 700; margin-top: 2px;
}
.step-list b { font-size: 15.5px; color: var(--blue-900); display: block; }
.step-list p { font-size: 13.5px; color: var(--ink-light); margin-top: 2px; }

/* 轮播 */
.carousel {
  position: relative; overflow: hidden; border-radius: 14px;
  border: 1px solid var(--border); box-shadow: var(--shadow);
  background: var(--white);
}
.carousel-track {
  display: flex; transition: transform 0.45s ease;
}
.carousel-slide {
  flex: 0 0 100%; min-width: 100%; position: relative;
  aspect-ratio: 16 / 9; background: var(--bg-warm);
}
.carousel-slide img {
  width: 100%; height: 100%; object-fit: contain; display: block;
  position: relative; z-index: 1;
}
.carousel-video {
  width: 100%; height: 100%; object-fit: contain; display: block;
  position: relative; z-index: 1; background: #0B1220;
}
.carousel-arrow {
  position: absolute; top: 50%; transform: translateY(-50%);
  z-index: 3; width: 38px; height: 38px; border-radius: 50%;
  border: none; background: rgba(255,255,255,0.92); color: var(--blue-900);
  font-size: 22px; cursor: pointer; line-height: 1;
  box-shadow: 0 2px 10px rgba(0,0,0,0.15); transition: background 0.15s;
}
.carousel-arrow:hover { background: #fff; }
.carousel-arrow.prev { left: 12px; }
.carousel-arrow.next { right: 12px; }
.carousel-dots {
  position: absolute; bottom: 10px; left: 0; right: 0; z-index: 3;
  display: flex; justify-content: center; gap: 8px;
}
.carousel-dots .dot {
  width: 8px; height: 8px; border-radius: 50%; background: rgba(255,255,255,0.55);
  cursor: pointer; transition: background 0.2s, transform 0.2s;
  box-shadow: 0 0 0 1px rgba(0,0,0,0.12);
}
.carousel-dots .dot.active { background: var(--orange-500); transform: scale(1.25); }

/* 图片占位（截图未提供时显示） */
.shot-ph {
  display: none; position: absolute; inset: 0; z-index: 0;
  align-items: center; justify-content: center; flex-direction: column; gap: 10px;
  color: var(--ink-light); font-size: 15px;
  background: linear-gradient(150deg, var(--blue-100) 0%, #F3F7FD 60%, var(--bg-warm) 100%);
}
.shot-ph span { font-size: 40px; }
.shot-ph-sm { position: relative; inset: auto; min-height: 160px; border-radius: 10px; margin-top: 14px; }
.shot-ph-tall { position: relative; inset: auto; aspect-ratio: 4/3; border-radius: 14px; }
.shot-ph-dark {
  position: relative; inset: auto; aspect-ratio: 16/10; border-radius: 14px;
  background: linear-gradient(150deg, rgba(255,255,255,0.12) 0%, rgba(255,255,255,0.05) 100%);
  border: 1px solid rgba(255,255,255,0.18); color: rgba(255,255,255,0.75);
}

/* 双模式卡片（全宽：文字左 + 媒体右） */
.mode-grid { display: flex; flex-direction: column; gap: 28px; margin-bottom: 64px; }
.mode-card {
  display: grid; grid-template-columns: 0.9fr 1.3fr; gap: 36px; align-items: center;
  background: var(--white); border: 1px solid var(--border); border-radius: 14px;
  padding: 34px 36px; transition: transform 0.18s, box-shadow 0.18s;
}
.mode-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-hover); }
.mode-text { min-width: 0; }
.mode-icon {
  width: 48px; height: 48px; border-radius: 12px; display: flex; align-items: center; justify-content: center;
  font-size: 24px; margin-bottom: 16px; background: var(--blue-100);
}
.mode-card:nth-child(2) .mode-icon { background: #FDEBE3; }
.mode-card h3 { font-size: 18px; color: var(--blue-900); margin-bottom: 10px; }
.mode-card p { font-size: 14.5px; color: var(--ink-light); }
.mode-media { min-width: 0; }
.mode-shot {
  width: 100%; border-radius: 12px; border: 1px solid var(--border);
  display: block;
}
.mode-media .shot-ph-sm { margin-top: 0; min-height: 240px; }

/* 模式卡视频（AI 推荐演示） */
.mode-video {
  position: relative; border-radius: 12px; overflow: hidden;
  border: 1px solid var(--border); background: #0B1220;
}
.mode-video video { width: 100%; display: block; aspect-ratio: 16/10; object-fit: contain; }
.mode-video-badge {
  position: absolute; top: 10px; left: 10px; z-index: 2;
  background: rgba(0,0,0,0.55); color: #fff; font-size: 12px;
  padding: 4px 10px; border-radius: 999px; letter-spacing: 0.3px;
  backdrop-filter: blur(4px); pointer-events: none;
}

/* 堆叠截图（学生交互 + 任务单导出） */
.feature-visual-stack { display: flex; flex-direction: column; gap: 20px; }
.shot-wrap {
  position: relative; border-radius: 12px; overflow: hidden;
  border: 1px solid var(--border); box-shadow: var(--shadow); background: var(--white);
}
.shot-wrap img { width: 100%; display: block; }
.shot-full { width: 100%; display: block; border-radius: 14px; border: 1px solid var(--border); box-shadow: var(--shadow); }

/* ===== 1 分钟开课（深色横幅）===== */
.quick {
  background: linear-gradient(150deg, #16335F 0%, #1F4E9C 60%, #2E6BC4 100%);
  color: #fff; padding: 88px 0;
}
.quick-grid {
  max-width: var(--maxw); margin: 0 auto; padding: 0 24px;
  display: grid; grid-template-columns: 1fr 1fr; gap: 56px; align-items: center;
}
.quick-copy h2 { font-size: 32px; line-height: 1.35; font-weight: 700; margin-bottom: 16px; }
.quick-copy p { font-size: 16px; color: rgba(255,255,255,0.85); margin-bottom: 30px; max-width: 480px; }
.quick-visual { position: relative; }
.quick-visual img {
  width: 100%; display: block; border-radius: 14px;
  border: 1px solid rgba(255,255,255,0.2); box-shadow: 0 18px 44px rgba(0,0,0,0.3);
}
.quick-videos { display: flex; flex-direction: column; gap: 18px; }
.quick-videos .mode-video { border-color: rgba(255,255,255,0.22); box-shadow: 0 18px 44px rgba(0,0,0,0.3); }

/* ===== 页脚 ===== */
.footer { background: var(--blue-900); color: rgba(255,255,255,0.8); padding: 48px 0 40px; font-size: 14px; }
.footer-inner { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }
.footer-top { display: flex; justify-content: space-between; align-items: flex-start; gap: 32px; flex-wrap: wrap; margin-bottom: 32px; }
.footer-brand img { height: 28px; width: auto; margin-bottom: 10px; }
.footer-links { display: flex; gap: 24px; }
.footer-links a { color: rgba(255,255,255,0.75); }
.footer-links a:hover { color: #fff; }
.footer-icp { border-top: 1px solid rgba(255,255,255,0.15); padding-top: 24px; text-align: center; color: rgba(255,255,255,0.6); font-size: 13px; }
.footer-icp a { color: rgba(255,255,255,0.75); }

/* ===== 文本页(隐私/协议) ===== */
.page { max-width: 800px; margin: 0 auto; padding: 56px 24px 88px; }
.page h1 { font-size: 30px; color: var(--blue-900); margin-bottom: 8px; }
.page .updated { font-size: 13px; color: var(--ink-light); margin-bottom: 36px; }
.page h2 { font-size: 19px; color: var(--blue-900); margin: 32px 0 12px; }
.page p, .page li { font-size: 15px; color: #374151; margin-bottom: 10px; }
.page ul, .page ol { padding-left: 24px; margin-bottom: 10px; }

/* ===== 响应式 ===== */
@media (max-width: 860px) {
  .hero { padding: 64px 0 56px; }
  .hero-grid { grid-template-columns: 1fr; gap: 36px; }
  .hero h1 { font-size: 32px; }
  .cards { grid-template-columns: 1fr; }
  .nav-links { display: none; }
  .hero-stats { flex-wrap: wrap; gap: 24px; }

  /* 功能块单列 */
  .feature-row { grid-template-columns: 1fr; gap: 36px; }
  .mode-grid { grid-template-columns: 1fr; }
  .quick { padding: 64px 0; }
  .quick-grid { grid-template-columns: 1fr; gap: 36px; }
  .quick-copy h2 { font-size: 26px; }
  .carousel-slide { aspect-ratio: 4/3; }
  .mode-card { grid-template-columns: 1fr; gap: 20px; padding: 26px 24px; }
  .plan-step { padding: 6px 12px 6px 8px; font-size: 12.5px; }
}

@media (max-width: 480px) {
  .carousel-slide { aspect-ratio: 1/1; }
}