/* =====================================================
   简课官网样式表 v2
   设计语言: 单一天蓝强调 + 中性底色 + Bento 布局 + 微动效
   ===================================================== */

:root {
  --primary: #1f7ae0;
  --primary-deep: #1557a8;
  --primary-soft: #e8f1fd;
  --accent: #1f7ae0;
  --text: #1c2632;
  --text-light: #5b6b7c;
  --bg: #f7f9fc;
  --surface: #ffffff;
  --border: #e3e9f0;
  --hero-grad-a: #eaf3fd;
  --hero-grad-b: #f7fafd;
  --radius-lg: 24px;
  --radius-md: 16px;
  --shadow-soft: 0 18px 40px -18px rgba(31, 90, 160, 0.18);
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  --font: "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei",
    -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: var(--font);
  color: var(--text);
  background: var(--bg);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: 1120px;
  margin: 0 auto;
  padding: 0 24px;
}

a { color: var(--primary); text-decoration: none; }
a:hover { color: var(--primary-deep); }
img { display: block; max-width: 100%; }

/* ---------------- 按钮 ---------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 26px;
  border-radius: 999px;
  font-family: var(--font);
  font-size: 15px;
  font-weight: 600;
  line-height: 1;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform 0.18s var(--ease), box-shadow 0.25s var(--ease),
    background 0.25s var(--ease), color 0.25s var(--ease);
  will-change: transform;
}
.btn:active { transform: translateY(1px) scale(0.985); }
.btn-primary {
  background: var(--primary);
  color: #fff;
  box-shadow: 0 10px 24px -10px rgba(31, 122, 224, 0.55);
}
.btn-primary:hover { background: var(--primary-deep); color: #fff; transform: translateY(-1px); }
.btn-ghost {
  background: transparent;
  color: var(--primary);
  border-color: rgba(31, 122, 224, 0.45);
}
.btn-ghost:hover { background: var(--primary-soft); transform: translateY(-1px); }
.btn-lg { padding: 15px 34px; font-size: 16px; }

/* ---------------- 顶部导航 ---------------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 60;
  background: rgba(255, 255, 255, 0.82);
  backdrop-filter: blur(14px) saturate(1.4);
  border-bottom: 1px solid var(--border);
  transition: box-shadow 0.3s var(--ease);
}
.nav.is-scrolled { box-shadow: 0 8px 24px -16px rgba(23, 59, 99, 0.28); }
.nav-inner { display: flex; align-items: center; justify-content: space-between; height: 66px; }
.brand { display: inline-flex; align-items: center; gap: 10px; font-weight: 700; font-size: 19px; color: var(--text); }
.brand img { width: 32px; height: 32px; border-radius: 8px; box-shadow: 0 4px 10px -4px rgba(31, 122, 224, 0.5); }
.menu { display: flex; align-items: center; gap: 26px; }
.menu a { color: var(--text); font-size: 15px; font-weight: 500; position: relative; padding: 6px 0; }
.menu a:hover { color: var(--primary); }
.menu a::after {
  content: "";
  position: absolute;
  left: 0; bottom: 0;
  width: 0; height: 2px;
  background: var(--primary);
  border-radius: 2px;
  transition: width 0.25s var(--ease);
}
.menu a:hover::after { width: 100%; }
.nav-cta { padding: 9px 20px; font-size: 14px; }

.menu-toggle {
  display: none;
  background: none;
  border: 1px solid var(--border);
  border-radius: 10px;
  width: 40px; height: 40px;
  align-items: center; justify-content: center;
  cursor: pointer;
}
.menu-toggle svg { width: 20px; height: 20px; stroke: var(--text); }

/* ---------------- Hero 首屏（非居中·左右分栏） ---------------- */
.hero {
  min-height: 100dvh;
  background:
    radial-gradient(1200px 600px at 85% 0%, rgba(120, 190, 255, 0.16), transparent 60%),
    radial-gradient(900px 500px at 0% 100%, rgba(160, 210, 255, 0.14), transparent 55%),
    linear-gradient(180deg, var(--hero-grad-a), var(--hero-grad-b) 70%);
  display: flex;
  align-items: center;
  padding: 96px 0 80px;
}
.hero-inner {
  display: grid;
  grid-template-columns: 1.05fr 0.95fr;
  gap: 56px;
  align-items: center;
}
.hero-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 13.5px;
  font-weight: 600;
  color: var(--primary);
  background: #fff;
  border: 1px solid var(--border);
  padding: 7px 14px;
  border-radius: 999px;
  margin-bottom: 22px;
  box-shadow: var(--shadow-soft);
}
.hero-eyebrow .dot {
  width: 7px; height: 7px; border-radius: 50%;
  background: var(--primary);
  animation: pulse 2.2s var(--ease) infinite;
}
@keyframes pulse { 0%, 100% { opacity: 1; } 50% { opacity: 0.35; } }

.hero-text h1 {
  font-size: clamp(38px, 5vw, 56px);
  line-height: 1.16;
  letter-spacing: -0.02em;
  font-weight: 800;
  margin-bottom: 20px;
  color: var(--text);
}
.hero-text h1 .accent {
  color: var(--primary);
  background: linear-gradient(90deg, var(--primary), #5aa8f5);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.hero-text .lead {
  font-size: 17px;
  color: var(--text-light);
  max-width: 46ch;
  margin-bottom: 30px;
}
.hero-actions { display: flex; gap: 14px; flex-wrap: wrap; }
.hero-tip { margin-top: 22px; font-size: 13.5px; color: var(--text-light); }
.hero-tip b { color: var(--primary-deep); font-weight: 600; }

.hero-visual { position: relative; display: flex; justify-content: center; align-items: center; }
.hero-phone {
  position: relative;
  width: min(300px, 60vw);
  border-radius: 34px;
  padding: 12px;
  background: #0e1622;
  box-shadow: 0 36px 80px -30px rgba(12, 34, 60, 0.55),
    inset 0 0 0 1px rgba(255, 255, 255, 0.08);
  transform: rotate(3deg);
  transition: transform 0.6s var(--ease);
}
.hero-phone:hover { transform: rotate(0deg) translateY(-6px); }
.hero-phone .screen {
  border-radius: 24px;
  overflow: hidden;
  aspect-ratio: 9 / 19;
  background: #fff;
}
.hero-phone .screen img { width: 100%; height: 100%; object-fit: cover; }
.hero-phone::before {
  content: "";
  position: absolute;
  top: 10px; left: 50%;
  transform: translateX(-50%);
  width: 90px; height: 16px;
  border-radius: 999px;
  background: #0e1622;
  z-index: 2;
}
.hero-glow {
  position: absolute;
  width: 420px; height: 420px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(31, 122, 224, 0.14), transparent 65%);
  filter: blur(10px);
  z-index: 0;
  pointer-events: none;
  animation: drift 9s ease-in-out infinite alternate;
}
@keyframes drift {
  from { transform: translate(-10px, -6px) scale(1); }
  to { transform: translate(14px, 10px) scale(1.06); }
}

/* Hero 图形化 App 卡（无截图） */
.hero-appcard {
  position: relative;
  z-index: 1;
  width: min(320px, 70vw);
  border-radius: 28px;
  padding: 30px 26px 26px;
  background: rgba(255, 255, 255, 0.72);
  border: 1px solid rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(14px);
  box-shadow:
    inset 0 1px 0 rgba(255, 255, 255, 0.9),
    0 34px 70px -30px rgba(23, 59, 99, 0.4);
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  transform: rotate(-2deg);
  transition: transform 0.6s var(--ease);
}
.hero-appcard:hover { transform: rotate(0deg) translateY(-6px); }
.hero-appicon {
  width: 96px; height: 96px;
  border-radius: 24px;
  overflow: hidden;
  background: #fff;
  box-shadow: 0 14px 30px -12px rgba(31, 122, 224, 0.5);
  margin-bottom: 16px;
}
.hero-appicon img { width: 100%; height: 100%; }
.hero-apptext { display: flex; flex-direction: column; gap: 4px; margin-bottom: 22px; }
.app-name { font-size: 26px; font-weight: 800; letter-spacing: -0.02em; color: var(--text); }
.app-slogan { font-size: 13.5px; color: var(--text-light); }
.hero-appgrid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  width: 100%;
}
.hero-appgrid span {
  aspect-ratio: 1;
  border-radius: 12px;
  background: var(--primary-soft);
  border: 1px solid #d4e7f8;
}
.hero-appgrid span:nth-child(1) { background: linear-gradient(135deg, #1f7ae0, #5aa8f5); }
.hero-appgrid span:nth-child(5) { background: linear-gradient(135deg, #1f7ae0, #5aa8f5); }
.hero-appgrid span:nth-child(9) { background: linear-gradient(135deg, #1f7ae0, #5aa8f5); }

.hero-badge-float {
  position: absolute;
  z-index: 3;
  background: rgba(255, 255, 255, 0.94);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 10px 14px;
  font-size: 13px;
  font-weight: 600;
  color: var(--text);
  box-shadow: var(--shadow-soft);
  display: flex;
  align-items: center;
  gap: 8px;
  animation: floaty 5.5s ease-in-out infinite;
  backdrop-filter: blur(6px);
}
.hero-badge-float svg { width: 16px; height: 16px; stroke: var(--primary); }
.hero-badge-float.b1 { top: 12%; left: -6%; animation-delay: 0s; }
.hero-badge-float.b2 { bottom: 16%; right: -4%; animation-delay: 1.4s; }
@keyframes floaty {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-9px); }
}

/* ---------------- 通用区块 ---------------- */
.section { padding: 96px 0; }
.section-head { max-width: 640px; margin: 0 auto 56px; text-align: center; }
.section-kicker {
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--primary);
  margin-bottom: 12px;
}
.section-head h2 { font-size: clamp(28px, 3.4vw, 36px); letter-spacing: -0.02em; font-weight: 800; margin-bottom: 12px; }
.section-head p { color: var(--text-light); font-size: 16px; }

/* ---------------- 功能特性：Bento 布局（3+1 横条） ---------------- */
.features { background: var(--bg); }
.bento {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-auto-rows: 1fr;
  gap: 20px;
}
.bento-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 30px 28px;
  transition: transform 0.3s var(--ease), box-shadow 0.35s var(--ease), border-color 0.3s;
}
.bento-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-soft);
  border-color: #c6ddf5;
}
.bento-card .b-icon {
  width: 46px; height: 46px;
  border-radius: 13px;
  background: var(--primary-soft);
  display: flex; align-items: center; justify-content: center;
  margin-bottom: 18px;
}
.bento-card .b-icon svg { width: 23px; height: 23px; stroke: var(--primary); stroke-width: 1.7; fill: none; stroke-linecap: round; stroke-linejoin: round; }
.bento-card h3 { font-size: 17.5px; font-weight: 700; margin-bottom: 8px; }
.bento-card p { font-size: 14.5px; color: var(--text-light); line-height: 1.6; }
.bento-wide {
  grid-column: span 3;
  display: grid;
  grid-template-columns: 1.2fr 1fr;
  gap: 28px;
  align-items: center;
  padding: 34px 36px;
}
.bento-wide .b-text h3 { font-size: 19px; margin-bottom: 8px; }
.bento-wide .b-text p { font-size: 14.5px; color: var(--text-light); }
.bento-chip {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--primary-soft);
  color: var(--primary-deep);
  font-size: 13.5px;
  font-weight: 600;
  padding: 8px 14px;
  border-radius: 999px;
}

/* ---------------- 截图区（横向滚动画廊） ---------------- */
.screens { background: linear-gradient(180deg, var(--bg), #eef4fb 100%); }
.screen-scroll {
  display: grid;
  grid-auto-flow: column;
  grid-auto-columns: 250px;
  gap: 22px;
  overflow-x: auto;
  padding: 12px 4px 26px;
  scroll-snap-type: x mandatory;
  scrollbar-width: thin;
  scrollbar-color: #c4d8ee transparent;
}
.screen-item {
  scroll-snap-align: start;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 14px;
  transition: transform 0.3s var(--ease), box-shadow 0.35s var(--ease);
}
.screen-item:hover { transform: translateY(-6px); box-shadow: var(--shadow-soft); }
.screen-item .frame {
  border-radius: 18px;
  overflow: hidden;
  aspect-ratio: 9 / 19;
  background: #eaf1f9;
}
.screen-item .frame img { width: 100%; height: 100%; object-fit: cover; }
.screen-item figcaption {
  padding: 12px 6px 4px;
  font-size: 14px;
  font-weight: 600;
  color: var(--text);
}
.screen-item .cap-sub { font-size: 12.5px; color: var(--text-light); font-weight: 400; }

/* ---------------- 下载区 ---------------- */
.download { background: var(--surface); }
.download-buttons {
  display: flex;
  justify-content: center;
  gap: 18px;
  flex-wrap: wrap;
  margin-bottom: 44px;
}
.btn-download {
  display: inline-flex;
  align-items: center;
  gap: 14px;
  border-radius: var(--radius-md);
  padding: 15px 28px;
  color: #fff;
  text-align: left;
  font-size: 15px;
  border: none;
  box-shadow: 0 14px 30px -16px rgba(13, 40, 70, 0.5);
  transition: transform 0.2s var(--ease), box-shadow 0.3s var(--ease), filter 0.2s;
}
.btn-download:hover { transform: translateY(-2px); filter: brightness(1.06); color: #fff; }
.btn-download:active { transform: translateY(0) scale(0.99); }
.btn-download small { display: block; font-size: 12px; opacity: 0.85; font-weight: 400; }
.btn-download .dl-icon { width: 34px; height: 34px; flex: none; }
.btn-download .dl-icon svg { width: 100%; height: 100%; stroke: #fff; fill: none; stroke-width: 1.7; stroke-linecap: round; stroke-linejoin: round; }
.btn-android { background: linear-gradient(135deg, #16a34a, #15803d); }
.btn-huawei { background: linear-gradient(135deg, #1f7ae0, #1557a8); }

.download-qr-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  margin-bottom: 40px;
}
.download-qr-wrap .qr-note { font-size: 13.5px; color: var(--text-light); }
.qr-placeholder {
  width: 150px; height: 150px;
  border-radius: var(--radius-md);
  border: 2px dashed #b7cde4;
  background: var(--bg);
  display: flex; flex-direction: column;
  align-items: center; justify-content: center;
  color: var(--text-light); font-size: 13px;
}
.qr-placeholder small { opacity: 0.75; font-size: 11.5px; margin-top: 4px; }

.version-box {
  max-width: 600px;
  margin: 0 auto;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 26px 30px;
}
.version-box h3 { font-size: 17px; margin-bottom: 6px; }
.version-box .ver-meta { font-size: 13px; color: var(--text-light); margin-bottom: 14px; }
.changelog { border-top: 1px solid var(--border); margin-top: 12px; padding-top: 14px; }
.changelog-title { font-weight: 700; font-size: 13.5px; margin-bottom: 6px; }
.changelog ul { padding-left: 20px; }
.changelog li { font-size: 13.5px; color: var(--text-light); margin-bottom: 4px; }

/* ---------------- FAQ ---------------- */
.faq { background: var(--bg); }
.faq-list { max-width: 780px; margin: 0 auto; display: flex; flex-direction: column; gap: 12px; }
.faq-item {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 20px 24px;
  transition: border-color 0.25s, box-shadow 0.3s var(--ease);
}
.faq-item:hover { border-color: #c6ddf5; box-shadow: var(--shadow-soft); }
.faq-item h3 { font-size: 15px; margin-bottom: 6px; }
.faq-item h3 .q { color: var(--primary); margin-right: 4px; }
.faq-item p { font-size: 14.5px; color: var(--text-light); }

/* ---------------- CTA ---------------- */
.cta-band {
  position: relative;
  overflow: hidden;
  background: linear-gradient(135deg, #1557a8, #1f7ae0 55%, #3f94ef);
  color: #fff;
  text-align: center;
  padding: 84px 0;
}
.cta-band::before {
  content: "";
  position: absolute;
  width: 480px; height: 480px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.08);
  top: -220px; right: -140px;
}
.cta-band::after {
  content: "";
  position: absolute;
  width: 340px; height: 340px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.07);
  bottom: -170px; left: -100px;
}
.cta-band h2 { font-size: clamp(26px, 3.2vw, 34px); margin-bottom: 10px; position: relative; z-index: 1; }
.cta-band p { opacity: 0.9; margin-bottom: 26px; position: relative; z-index: 1; }
.cta-band .btn-primary { background: #fff; color: var(--primary-deep); box-shadow: 0 14px 30px -14px rgba(0, 0, 0, 0.4); }
.cta-band .btn-primary:hover { background: #eef4fb; color: var(--primary-deep); }

/* ---------------- 页脚 ---------------- */
.footer { background: #101a28; color: #8ca0b4; padding: 56px 0 44px; }
.footer-inner { display: flex; flex-direction: column; gap: 18px; align-items: center; }
.footer-brand { display: inline-flex; align-items: center; gap: 10px; color: #fff; font-weight: 700; font-size: 17px; }
.footer-brand img { width: 28px; height: 28px; border-radius: 7px; }
.footer-links { display: flex; gap: 26px; flex-wrap: wrap; justify-content: center; }
.footer-links a { color: #8ca0b4; font-size: 14px; }
.footer-links a:hover { color: #fff; }
.footer-copy { text-align: center; font-size: 13px; line-height: 1.8; }
.footer-copy a { color: #8ca0b4; }

/* ---------------- 滚动渐显 ---------------- */
.reveal {
  opacity: 0;
  transform: translateY(22px);
  transition: opacity 0.7s var(--ease), transform 0.7s var(--ease);
}
.reveal.in-view { opacity: 1; transform: translateY(0); }

/* ---------------- 反馈页 / 隐私页 ---------------- */
.page-hero {
  background: linear-gradient(180deg, var(--hero-grad-a), var(--bg));
  padding: 72px 0 56px;
  text-align: center;
}
.page-hero h1 { font-size: clamp(28px, 3.4vw, 36px); font-weight: 800; margin-bottom: 12px; letter-spacing: -0.02em; }
.page-hero .lead { color: var(--text-light); max-width: 560px; margin: 0 auto; font-size: 16px; }
.page-body { background: var(--bg); }
.brand-name { font-weight: 700; }
.legal-back { margin-top: 30px; padding-top: 20px; border-top: 1px solid var(--border); }
.legal-back a { font-size: 14.5px; font-weight: 600; }
.feedback-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 22px;
  max-width: 920px;
  margin: 0 auto 72px;
}
.feedback-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 30px;
  box-shadow: var(--shadow-soft);
}
.feedback-card h2 { font-size: 18px; display: flex; align-items: center; gap: 10px; margin-bottom: 12px; }
.feedback-card h2 .fi { width: 34px; height: 34px; border-radius: 10px; background: var(--primary-soft); display: inline-flex; align-items: center; justify-content: center; }
.feedback-card h2 .fi svg { width: 17px; height: 17px; stroke: var(--primary); stroke-width: 1.8; fill: none; stroke-linecap: round; stroke-linejoin: round; }
.feedback-card p { font-size: 14.5px; color: var(--text-light); margin-bottom: 18px; }
.feedback-note { font-size: 13px !important; margin-top: 12px; }
.feedback-mail {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 15px;
  font-weight: 600;
  color: var(--primary);
  border: 1px solid var(--border);
  padding: 9px 16px;
  border-radius: 999px;
}
.feedback-mail:hover { background: var(--primary-soft); border-color: #c6ddf5; }

.legal {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 44px 50px;
  margin: 36px auto 72px;
  max-width: 860px;
  box-shadow: var(--shadow-soft);
}
.legal h1 { font-size: 28px; margin-bottom: 8px; }
.legal-updated { color: var(--text-light); font-size: 13px; margin-bottom: 22px; }
.legal-lead { margin-bottom: 22px; }
.legal h2 { font-size: 18px; margin: 26px 0 12px; color: var(--primary-deep); }
.legal p, .legal li { font-size: 14.5px; color: #35434f; }
.legal ul { padding-left: 22px; margin-bottom: 12px; }
.legal li { margin-bottom: 6px; }
.legal-note {
  background: #fff8e6;
  border-left: 4px solid #e0a800;
  padding: 10px 14px;
  font-size: 13px;
  color: #7a5b00;
  border-radius: 8px;
}

/* ---------------- 移动端 ---------------- */
@media (max-width: 900px) {
  .hero { padding-top: 72px; }
  .hero-inner { grid-template-columns: 1fr; gap: 44px; }
  .hero-text { text-align: left; }
  .hero-actions, .hero-tip { text-align: left; }
  .hero-visual { order: -1; }
  .menu {
    display: none;
    position: absolute;
    top: 66px; left: 0; right: 0;
    background: #fff;
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    align-items: stretch;
    padding: 12px 22px 18px;
    gap: 4px;
    box-shadow: 0 20px 30px -24px rgba(13, 40, 70, 0.3);
  }
  .menu.open { display: flex; }
  .menu a { padding: 11px 6px; font-size: 15.5px; }
  .menu-toggle { display: inline-flex; }
  .nav-cta { display: none; }
  .bento { grid-template-columns: 1fr; }
  .bento-wide { grid-template-columns: 1fr; grid-column: span 1; padding: 26px 24px; }
  .feedback-grid { grid-template-columns: 1fr; }
  .hero-badge-float.b1 { left: 2%; }
  .hero-badge-float.b2 { right: 2%; }
}