/* ===========================================================
   聊缘AI · Landing Page
   配色取自 App Logo：深黑底 + 白色主色 + 双圆点缀
   =========================================================== */

:root {
  /* 主题色（可直接改这里全站联动） */
  --c-bg: #141416;          /* 主背景 —— 比logo底稍深 */
  --c-bg-2: #1c1c1f;        /* 次背景 */
  --c-bg-3: #252529;        /* 卡片/分割 */
  --c-surface: #1e1e21;     /* 卡片 */
  --c-line: #2c2c30;        /* 边框 */

  --c-text: #f4f4f6;        /* 主文字 */
  --c-text-2: #b8b8bd;      /* 次文字 */
  --c-text-3: #8a8a90;      /* 辅助文字 */

  --c-accent: #ffffff;      /* 主强调（logo白色） */
  --c-accent-soft: rgba(255, 255, 255, 0.08);

  /* 点缀色（双圆点对应的柔和白辉光） */
  --c-dot: #ffffff;
  --c-glow: 0 0 40px rgba(255, 255, 255, 0.15);

  --radius-lg: 20px;
  --radius-md: 14px;
  --radius-sm: 10px;

  --shadow-1: 0 10px 30px rgba(0, 0, 0, 0.35);
  --shadow-2: 0 30px 60px rgba(0, 0, 0, 0.5);

  --container: 1200px;

  --ease: cubic-bezier(0.4, 0, 0.2, 1);
}

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

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC",
               "Microsoft YaHei", "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--c-bg);
  color: var(--c-text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }
button { font-family: inherit; border: none; background: none; cursor: pointer; color: inherit; }

.container {
  width: 100%;
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 24px;
}

/* ================= 顶部导航 ================= */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  transition: background .35s var(--ease), backdrop-filter .35s var(--ease),
              box-shadow .35s var(--ease);
}
.navbar.scrolled {
  background: rgba(20, 20, 22, 0.85);
  backdrop-filter: saturate(180%) blur(16px);
  -webkit-backdrop-filter: saturate(180%) blur(16px);
  box-shadow: 0 1px 0 var(--c-line);
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
}
.brand-logo {
  width: 36px;
  height: 36px;
  border-radius: 10px;
  background: var(--c-bg-3);      /* 占位底色，方便看到img空 */
  border: 1px solid var(--c-line);
  object-fit: cover;
}
.brand-name {
  font-size: 18px;
  font-weight: 700;
  letter-spacing: 0.5px;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 8px;
}
.nav-links a {
  padding: 8px 16px;
  font-size: 14px;
  color: var(--c-text-2);
  border-radius: 999px;
  transition: color .2s, background .2s;
}
.nav-links a:hover { color: var(--c-text); background: var(--c-accent-soft); }
.nav-cta {
  background: var(--c-text) !important;
  color: var(--c-bg) !important;
  font-weight: 600;
}
.nav-cta:hover { background: #e8e8ea !important; color: var(--c-bg) !important; }

.nav-toggle {
  display: none;
  width: 40px;
  height: 40px;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  padding: 0;
}
.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--c-text);
  margin: 0 auto;
  transition: transform .3s var(--ease), opacity .2s;
}
.nav-toggle.active span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle.active span:nth-child(2) { opacity: 0; }
.nav-toggle.active span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ================= Hero 首屏 ================= */
.hero {
  position: relative;
  padding: 140px 0 100px;
  overflow: hidden;
}
.hero-bg {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse at 15% 20%, rgba(255,255,255,0.07), transparent 55%),
    radial-gradient(ellipse at 85% 80%, rgba(255,255,255,0.05), transparent 50%),
    linear-gradient(180deg, var(--c-bg) 0%, var(--c-bg-2) 100%);
  pointer-events: none;
}
.hero-bg::before,
.hero-bg::after {
  content: "";
  position: absolute;
  border-radius: 50%;
  filter: blur(40px);
  opacity: 0.25;
}
.hero-bg::before {
  width: 320px; height: 320px;
  background: #ffffff;
  top: -80px; right: -60px;
}
.hero-bg::after {
  width: 220px; height: 220px;
  background: #ffffff;
  bottom: -40px; left: -40px;
  opacity: 0.15;
}

.hero-inner {
  position: relative;
  display: grid;
  grid-template-columns: 1.1fr 1fr;
  gap: 60px;
  align-items: center;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 14px 6px 10px;
  background: var(--c-accent-soft);
  border: 1px solid var(--c-line);
  border-radius: 999px;
  font-size: 13px;
  color: var(--c-text-2);
  margin-bottom: 24px;
}
.hero-badge .dot {
  width: 8px; height: 8px;
  border-radius: 50%;
  background: var(--c-accent);
  box-shadow: 0 0 10px var(--c-accent);
}

.hero-title {
  font-size: clamp(36px, 5vw, 56px);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.5px;
  margin-bottom: 20px;
}
.hero-title .highlight {
  background: linear-gradient(120deg, #ffffff 0%, #d0d0d5 100%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  position: relative;
}

.hero-sub {
  font-size: 16px;
  color: var(--c-text-2);
  line-height: 1.8;
  margin-bottom: 32px;
  max-width: 540px;
}

.hero-meta {
  display: flex;
  align-items: center;
  gap: 28px;
  padding: 18px 24px;
  background: rgba(255,255,255,0.02);
  border: 1px solid var(--c-line);
  border-radius: var(--radius-md);
  margin-bottom: 32px;
  flex-wrap: wrap;
}
.meta-item { display: flex; flex-direction: column; gap: 2px; }
.meta-label { font-size: 12px; color: var(--c-text-3); }
.meta-value { font-size: 15px; font-weight: 600; }
.meta-divider {
  width: 1px; height: 28px;
  background: var(--c-line);
}

.hero-actions {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  margin-bottom: 48px;
}
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 26px;
  border-radius: 999px;
  font-size: 15px;
  font-weight: 600;
  transition: transform .2s var(--ease), box-shadow .2s, background .2s, color .2s;
  cursor: pointer;
}
.btn-primary {
  background: var(--c-text);
  color: var(--c-bg);
  box-shadow: 0 8px 24px rgba(255,255,255,0.15);
}
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 12px 32px rgba(255,255,255,0.25); }
.btn-ghost {
  background: transparent;
  color: var(--c-text);
  border: 1px solid var(--c-line);
}
.btn-ghost:hover { background: var(--c-accent-soft); transform: translateY(-2px); }

.hero-stats {
  display: flex;
  gap: 36px;
}
.stat { display: flex; flex-direction: column; }
.stat-num { font-size: 22px; font-weight: 700; letter-spacing: -0.5px; }
.stat-label { font-size: 13px; color: var(--c-text-3); }

/* Hero 手机叠放 */
.hero-visual {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 520px;
}
.phone-stack {
  position: relative;
  width: 300px;
  height: 560px;
  perspective: 1200px;
}
.phone {
  position: absolute;
  width: 260px;
  height: 520px;
  background: var(--c-bg-3);
  border: 2px solid var(--c-line);
  border-radius: 38px;
  overflow: hidden;
  box-shadow: var(--shadow-2);
  transition: transform .5s var(--ease), opacity .4s var(--ease);
}
.phone-notch {
  position: absolute;
  top: 8px; left: 50%;
  transform: translateX(-50%);
  width: 110px; height: 24px;
  background: var(--c-bg);
  border-radius: 14px;
  z-index: 5;
}
.phone-img {
  width: 100%; height: 100%;
  object-fit: cover;
  background: linear-gradient(160deg, #2a2a2e 0%, #1c1c1f 100%);
}

.phone-back {
  top: 0; left: 0;
  transform: rotate(-10deg) translateX(-60px) scale(0.85);
  opacity: 0.5;
  z-index: 1;
}
.phone-mid {
  top: 20px; left: 40px;
  transform: rotate(-4deg) translateX(-20px) scale(0.92);
  opacity: 0.75;
  z-index: 2;
}
.phone-front {
  top: 40px; left: 80px;
  transform: rotate(0deg) scale(1);
  z-index: 3;
}

.phone-stack:hover .phone-back { transform: rotate(-14deg) translateX(-110px) scale(0.8); opacity: 0.35; }
.phone-stack:hover .phone-mid  { transform: rotate(0deg) translateX(-15px) scale(0.95); opacity: 0.9; }
.phone-stack:hover .phone-front { transform: rotate(4deg) translateX(80px) scale(1.05); opacity: 1; }

.phone-caption {
  position: absolute;
  bottom: 0; left: 50%;
  transform: translateX(-50%);
  font-size: 12px;
  color: var(--c-text-3);
  letter-spacing: 0.5px;
  white-space: nowrap;
}

/* ================= Section 通用 ================= */
.section {
  padding: 100px 0;
  position: relative;
}
.section-head {
  text-align: center;
  margin-bottom: 56px;
}
.section-title {
  font-size: clamp(28px, 3.5vw, 40px);
  font-weight: 800;
  letter-spacing: -0.5px;
  margin-bottom: 12px;
}
.section-desc {
  font-size: 15px;
  color: var(--c-text-2);
}

/* ================= 功能特色 ================= */
.features { background: var(--c-bg-2); }

.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}

.feature-card {
  padding: 32px 28px;
  background: var(--c-surface);
  border: 1px solid var(--c-line);
  border-radius: var(--radius-lg);
  transition: transform .3s var(--ease), border-color .3s, box-shadow .3s;
}
.feature-card:hover {
  transform: translateY(-6px);
  border-color: rgba(255,255,255,0.2);
  box-shadow: 0 20px 50px rgba(0,0,0,0.4);
}
.feature-icon {
  width: 48px; height: 48px;
  display: grid; place-items: center;
  background: var(--c-accent-soft);
  border: 1px solid var(--c-line);
  border-radius: 14px;
  margin-bottom: 18px;
}
.feature-icon svg { width: 24px; height: 24px; color: var(--c-accent); }
.feature-card h3 { font-size: 18px; margin-bottom: 8px; font-weight: 700; }
.feature-card p { font-size: 14px; color: var(--c-text-2); line-height: 1.7; }

/* ================= 应用截图 ================= */
.screenshots { background: var(--c-bg); }

.shots-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}
.shot-card {
  position: relative;
  aspect-ratio: 9 / 16;
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: var(--c-bg-3);
  border: 1px solid var(--c-line);
  transition: transform .4s var(--ease), box-shadow .4s;
  cursor: pointer;
}
.shot-card:hover {
  transform: translateY(-6px) scale(1.02);
  box-shadow: var(--shadow-2);
  z-index: 2;
}
.shot-frame {
  position: absolute; inset: 0;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding-top: 40px;
}
.shot-notch {
  position: absolute;
  top: 10px; left: 50%;
  transform: translateX(-50%);
  width: 60px; height: 14px;
  background: var(--c-bg);
  border-radius: 10px;
  z-index: 3;
}
.shot-frame img {
  width: calc(100% - 16px);
  height: calc(100% - 16px);
  border-radius: 14px;
  object-fit: cover;
  background: linear-gradient(160deg, #2a2a2e 0%, #1c1c1f 100%);
  border: 1px solid var(--c-line);
  transition: transform .5s var(--ease), opacity .4s;
}
.shot-card:hover .shot-frame img { transform: scale(1.03); }

.shot-label {
  position: absolute;
  bottom: 16px; left: 50%;
  transform: translateX(-50%);
  padding: 6px 14px;
  background: rgba(20,20,22,0.85);
  backdrop-filter: blur(10px);
  border: 1px solid var(--c-line);
  border-radius: 999px;
  font-size: 13px;
  white-space: nowrap;
}

/* ================= 用户评价 ================= */
.reviews { background: var(--c-bg-2); }

.reviews-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
}
.review-card {
  padding: 28px;
  background: var(--c-surface);
  border: 1px solid var(--c-line);
  border-radius: var(--radius-lg);
  transition: border-color .3s, transform .3s var(--ease);
}
.review-card:hover { border-color: rgba(255,255,255,0.2); transform: translateY(-3px); }
.review-stars { color: #e0c87a; font-size: 14px; margin-bottom: 14px; letter-spacing: 2px; }
.review-text { font-size: 15px; color: var(--c-text-2); line-height: 1.8; margin-bottom: 20px; }
.review-user { display: flex; align-items: center; gap: 12px; }
.review-avatar {
  width: 40px; height: 40px;
  border-radius: 50%;
  background: linear-gradient(135deg, #2a2a2e, #1c1c1f);
  border: 1px solid var(--c-line);
  display: grid; place-items: center;
  font-weight: 700;
  font-size: 14px;
}
.review-name { font-weight: 600; font-size: 14px; }
.review-platform { font-size: 12px; color: var(--c-text-3); }

/* ================= FAQ ================= */
.faq { background: var(--c-bg); }

.faq-list {
  max-width: 780px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.faq-item {
  background: var(--c-surface);
  border: 1px solid var(--c-line);
  border-radius: var(--radius-md);
  overflow: hidden;
}
.faq-q {
  width: 100%;
  text-align: left;
  padding: 20px 24px;
  font-size: 15px;
  font-weight: 600;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  transition: background .2s;
}
.faq-q:hover { background: var(--c-accent-soft); }
.faq-arrow {
  font-size: 22px;
  font-weight: 400;
  color: var(--c-text-3);
  transition: transform .3s var(--ease);
  flex-shrink: 0;
}
.faq-item.open .faq-arrow { transform: rotate(45deg); }

.faq-a {
  max-height: 0;
  overflow: hidden;
  transition: max-height .4s var(--ease);
}
.faq-item.open .faq-a { max-height: 300px; }
.faq-a p {
  padding: 0 24px 20px;
  font-size: 14px;
  color: var(--c-text-2);
  line-height: 1.8;
}

/* ================= 下载模块 ================= */
.download {
  background: var(--c-bg-2);
  padding: 80px 0;
}
.download-inner {
  position: relative;
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 60px;
  align-items: center;
  padding: 56px;
  background:
    radial-gradient(ellipse at 0% 50%, rgba(255,255,255,0.06), transparent 60%),
    var(--c-surface);
  border: 1px solid var(--c-line);
  border-radius: 28px;
  overflow: hidden;
}
.download-inner::before {
  content: "";
  position: absolute;
  top: -100px; right: -100px;
  width: 300px; height: 300px;
  background: #ffffff;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.08;
  pointer-events: none;
}

.download-title {
  font-size: clamp(28px, 3.5vw, 42px);
  font-weight: 800;
  letter-spacing: -0.5px;
  margin-bottom: 10px;
}
.download-sub { font-size: 15px; color: var(--c-text-2); margin-bottom: 22px; }
.download-tags {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}
.download-tags span {
  padding: 6px 14px;
  background: var(--c-accent-soft);
  border: 1px solid var(--c-line);
  border-radius: 999px;
  font-size: 13px;
  color: var(--c-text-2);
}

.download-buttons {
  display: flex;
  flex-direction: column;
  gap: 14px;
  min-width: 220px;
}
.dl-btn {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 16px 22px;
  background: var(--c-bg-3);
  border: 1px solid var(--c-line);
  border-radius: var(--radius-md);
  transition: transform .25s var(--ease), border-color .25s, background .25s;
  color: var(--c-text);
}
.dl-btn:hover {
  transform: translateY(-3px);
  border-color: rgba(255,255,255,0.3);
  background: var(--c-bg);
}
.dl-icon {
  width: 42px; height: 42px;
  display: grid; place-items: center;
  background: var(--c-accent-soft);
  border-radius: 10px;
}
.dl-icon svg { width: 26px; height: 26px; color: var(--c-text); }
.dl-text { display: flex; flex-direction: column; }
.dl-small { font-size: 11px; color: var(--c-text-3); letter-spacing: 0.5px; }
.dl-os { font-size: 17px; font-weight: 700; }

.dl-android:hover { border-color: rgba(255,255,255,0.4); }
.dl-ios:hover { border-color: rgba(255,255,255,0.4); }

/* ================= 页脚 ================= */
.footer {
  padding: 48px 0 32px;
  background: var(--c-bg);
  border-top: 1px solid var(--c-line);
}
.footer-inner {
  display: grid;
  grid-template-columns: auto 1fr 1fr;
  align-items: center;
  gap: 24px;
}
.footer-brand { display: flex; align-items: center; gap: 12px; }
.footer-logo {
  width: 36px; height: 36px;
  border-radius: 10px;
  background: var(--c-bg-3);
  border: 1px solid var(--c-line);
}
.footer-name { font-weight: 700; font-size: 15px; }
.footer-desc { font-size: 12px; color: var(--c-text-3); }
.footer-links { display: flex; justify-content: center; gap: 24px; }
.footer-links a { font-size: 14px; color: var(--c-text-2); transition: color .2s; }
.footer-links a:hover { color: var(--c-text); }
.footer-copy { font-size: 12px; color: var(--c-text-3); text-align: right; }

/* ================= 入场动画 ================= */
.reveal {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity .8s var(--ease), transform .8s var(--ease);
}
.reveal.visible { opacity: 1; transform: translateY(0); }

/* ================= 响应式 ================= */
@media (max-width: 960px) {
  .hero { padding: 120px 0 80px; }
  .hero-inner { grid-template-columns: 1fr; gap: 50px; }
  .hero-visual { min-height: 440px; order: -1; }
  .phone-stack { transform: scale(0.85); }

  .features-grid { grid-template-columns: repeat(2, 1fr); }
  .shots-grid { grid-template-columns: 1fr; max-width: 320px; margin: 0 auto; }
  .reviews-grid { grid-template-columns: 1fr; }

  .download-inner { grid-template-columns: 1fr; padding: 40px 28px; gap: 32px; }
  .download-buttons { flex-direction: row; }
  .dl-btn { flex: 1; }

  .footer-inner { grid-template-columns: 1fr; text-align: center; }
  .footer-links { justify-content: center; }
  .footer-copy { text-align: center; }
}

@media (max-width: 640px) {
  .nav-links {
    position: fixed;
    top: 72px; left: 0; right: 0;
    background: rgba(20,20,22,0.98);
    backdrop-filter: blur(16px);
    flex-direction: column;
    align-items: stretch;
    padding: 16px;
    gap: 4px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.5);
    transform: translateY(-120%);
    transition: transform .35s var(--ease);
  }
  .nav-links.open { transform: translateY(0); }
  .nav-links a { padding: 14px 18px; border-radius: 10px; font-size: 15px; }
  .nav-cta { text-align: center; }
  .nav-toggle { display: flex; }

  .hero-meta { gap: 16px; padding: 14px 18px; }
  .meta-divider { display: none; }
  .hero-stats { gap: 20px; }
  .stat-num { font-size: 18px; }

  .features-grid { grid-template-columns: 1fr; }
  .section { padding: 72px 0; }

  .download-buttons { flex-direction: column; }
  .phone-stack { transform: scale(0.7); }
  .hero-visual { min-height: 380px; }
}