:root {
  --primary: #0066ff;
  --primary-dark: #0052cc;
  --secondary: #00d4aa;
  --dark: #1a1a2e;
  --light: #ffffff;
  --gray-50: #f8f9fa;
  --gray-100: #eef2f6;
  --gray-300: #d9e2ec;
  --gray-500: #6c7a89;
  --gray-700: #36414d;
  --text: #212529;
  --border: #e6ebf0;
  --shadow-sm: 0 8px 30px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 18px 40px rgba(0, 102, 255, 0.12);
  --radius-lg: 18px;
  --radius-md: 12px;
  --radius-sm: 10px;
  --transition: all 0.3s ease;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", sans-serif;
  line-height: 1.6;
  color: var(--text);
  background: linear-gradient(135deg, #f5f7fa 0%, #e4edf5 100%);
}

img {
  max-width: 100%;
  display: block;
}

a,
button {
  -webkit-tap-highlight-color: transparent;
}

a {
  text-decoration: none;
  color: inherit;
}

button {
  font: inherit;
}

.container {
  width: min(1200px, calc(100% - 40px));
  margin: 0 auto;
}

/* topbar */
.topbar {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: rgba(255,255,255,0.88);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid rgba(0,0,0,0.05);
}

.topbar-inner {
  min-height: 74px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 14px;
}

.brand-icon {
  width: 46px;
  height: 46px;
  border-radius: 12px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-weight: 800;
  font-size: 22px;
  flex-shrink: 0;
}

.brand-text {
  display: flex;
  flex-direction: column;
  line-height: 1.2;
}

.brand-text strong {
  font-size: 1.2rem;
  color: var(--dark);
}

.brand-text small {
  color: var(--gray-500);
  font-size: 0.85rem;
}

.nav {
  display: flex;
  align-items: center;
  gap: 24px;
}

.nav-link {
  color: var(--gray-700);
  font-weight: 500;
  position: relative;
  padding: 6px 0;
  transition: var(--transition);
}

.nav-link::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -2px;
  width: 0;
  height: 2px;
  background: var(--primary);
  transition: width .25s ease;
}

.nav-link:hover {
  color: var(--primary);
}

.nav-link:hover::after,
.nav-link.active::after {
  width: 100%;
}

.menu-btn {
  display: none;
  width: 46px;
  height: 46px;
  border: none;
  background: transparent;
  border-radius: 10px;
  cursor: pointer;
  padding: 0;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  gap: 5px;
}

.menu-btn span {
  width: 22px;
  height: 2px;
  background: var(--dark);
  border-radius: 2px;
  transition: var(--transition);
}

.menu-btn.open span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.menu-btn.open span:nth-child(2) {
  opacity: 0;
}

.menu-btn.open span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* hero */
.hero {
  padding: 96px 0 70px;
}

.hero-inner {
  display: grid;
  grid-template-columns: 1.05fr 0.95fr;
  gap: 44px;
  align-items: center;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 18px;
  border-radius: 999px;
  background: rgba(0, 102, 255, 0.08);
  color: var(--primary);
  font-weight: 600;
  margin-bottom: 18px;
}

.hero-title {
  margin: 0 0 18px;
  font-size: clamp(2.4rem, 5vw, 3.7rem);
  line-height: 1.12;
  font-weight: 800;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-desc {
  margin: 0 0 28px;
  font-size: 1.12rem;
  color: var(--gray-700);
  max-width: 720px;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  margin-bottom: 24px;
}

.hero-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
  color: var(--gray-500);
  font-size: 0.96rem;
}

.hero-card {
  position: relative;
}

.window {
  border-radius: 22px;
  overflow: hidden;
  background: #fff;
  box-shadow: var(--shadow-md);
  border: 1px solid rgba(0,0,0,0.04);
}

.window-bar {
  height: 52px;
  background: #f3f5f8;
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 0 18px;
}

.window-bar span {
  width: 12px;
  height: 12px;
  border-radius: 50%;
}

.window-bar span:nth-child(1) { background: #ff5f57; }
.window-bar span:nth-child(2) { background: #febc2e; }
.window-bar span:nth-child(3) { background: #28c840; }

.window-bar em {
  margin-left: auto;
  font-style: normal;
  color: var(--gray-500);
  font-size: 0.86rem;
}

.window-body {
  padding: 42px 34px;
  text-align: center;
}

.status-ring {
  width: 110px;
  height: 110px;
  margin: 0 auto 20px;
  border-radius: 50%;
  background: linear-gradient(135deg, rgba(0,102,255,0.12), rgba(0,212,170,0.12));
  border: 3px solid rgba(0,102,255,0.16);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 42px;
  color: var(--primary);
  font-weight: 800;
}

.window-body h2 {
  margin: 0 0 12px;
  font-size: 1.5rem;
  color: var(--dark);
}

.window-body p {
  margin: 0 0 22px;
  color: var(--gray-500);
}

.window-tags {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 10px;
}

.window-tags span {
  background: var(--gray-100);
  padding: 8px 14px;
  border-radius: 999px;
  color: var(--gray-700);
  font-size: 0.9rem;
}

/* buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 54px;
  padding: 0 28px;
  border-radius: 12px;
  font-weight: 700;
  cursor: pointer;
  transition: var(--transition);
  border: none;
  text-align: center;
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: #fff;
  box-shadow: 0 15px 30px rgba(0, 102, 255, 0.22);
}

.btn-primary:hover {
  transform: translateY(-3px);
  box-shadow: 0 20px 34px rgba(0, 102, 255, 0.28);
}

.btn-secondary {
  background: transparent;
  color: var(--primary);
  border: 2px solid rgba(0, 102, 255, 0.22);
}

.btn-secondary:hover {
  transform: translateY(-3px);
  background: rgba(0, 102, 255, 0.06);
}

/* stats */
.stats {
  padding: 0 0 40px;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 18px;
}

.stat {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 24px;
  text-align: center;
  box-shadow: 0 8px 24px rgba(0,0,0,0.03);
}

.stat strong {
  display: block;
  font-size: 1.3rem;
  color: var(--dark);
  margin-bottom: 6px;
}

.stat span {
  color: var(--gray-500);
}

/* shared section */
.download-section,
.features-section,
.promise-section,
.guide-section,
.faq-section {
  padding: 82px 0;
}

.features-section {
  background: #fff;
}

.promise-section,
.guide-section {
  background: var(--gray-50);
}

.section-head {
  text-align: center;
  margin-bottom: 54px;
}

.section-head h2 {
  margin: 0 0 14px;
  font-size: clamp(2rem, 4vw, 2.8rem);
  color: var(--dark);
}

.section-head p {
  margin: 0 auto;
  max-width: 760px;
  color: var(--gray-500);
  font-size: 1.05rem;
}

/* download cards */
.download-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 28px;
}

.download-card {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 34px 28px;
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
}

.download-card:hover {
  transform: translateY(-6px);
  box-shadow: 0 18px 34px rgba(0,0,0,0.06);
}

.card-icon {
  width: 84px;
  height: 84px;
  border-radius: 22px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 42px;
  margin-bottom: 20px;
  background: linear-gradient(135deg, rgba(0,102,255,0.08), rgba(0,212,170,0.08));
}

.download-card h3 {
  margin: 0 0 10px;
  font-size: 1.45rem;
  color: var(--dark);
}

.download-card p {
  margin: 0 0 18px;
  color: var(--gray-500);
}

.card-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 16px;
  margin-bottom: 18px;
}

.card-meta span {
  font-size: 0.92rem;
  color: var(--primary);
  background: rgba(0, 102, 255, 0.07);
  padding: 7px 12px;
  border-radius: 999px;
}

.progress-wrap {
  display: none;
  width: 100%;
  height: 8px;
  background: var(--gray-100);
  border-radius: 999px;
  overflow: hidden;
  margin: 18px 0 20px;
}

.empty-progress {
  display: block;
  visibility: hidden;
  height: 8px;
  margin: 18px 0 20px;
}

.progress-bar {
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--secondary));
  border-radius: 999px;
  transition: width .25s linear;
}

/* feature/promise */
.feature-grid,
.promise-grid,
.guide-grid {
  display: grid;
  gap: 28px;
}

.feature-grid,
.promise-grid {
  grid-template-columns: repeat(3, 1fr);
}

.guide-grid {
  grid-template-columns: repeat(3, 1fr);
}

.feature-card,
.promise-card,
.guide-card {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px 26px;
  text-align: center;
  box-shadow: 0 8px 24px rgba(0,0,0,0.03);
  transition: var(--transition);
}

.feature-card:hover,
.promise-card:hover,
.guide-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-sm);
}

.feature-icon {
  width: 74px;
  height: 74px;
  border-radius: 20px;
  margin: 0 auto 18px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 34px;
}

.feature-card h3,
.promise-card h3,
.guide-card h3 {
  margin: 0 0 12px;
  font-size: 1.3rem;
  color: var(--dark);
}

.feature-card p,
.promise-card p,
.guide-card p {
  margin: 0;
  color: var(--gray-500);
}

.step {
  width: 60px;
  height: 60px;
  margin: 0 auto 18px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-weight: 800;
  font-size: 1.4rem;
}

/* faq */
.faq-list {
  max-width: 920px;
  margin: 0 auto;
}

.faq-item {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  margin-bottom: 16px;
  overflow: hidden;
  transition: var(--transition);
}

.faq-item.active {
  box-shadow: var(--shadow-sm);
  border-color: rgba(0,102,255,0.2);
}

.faq-question {
  width: 100%;
  padding: 22px 24px;
  border: none;
  background: #fff;
  color: var(--dark);
  font-weight: 700;
  font-size: 1rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  text-align: left;
  cursor: pointer;
}

.faq-question:hover {
  color: var(--primary);
}

.faq-icon {
  font-size: 1.3rem;
  line-height: 1;
  color: var(--primary);
  flex-shrink: 0;
  transition: transform .25s ease;
}

.faq-item.active .faq-icon {
  transform: rotate(45deg);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  padding: 0 24px;
  color: var(--gray-500);
  line-height: 1.8;
  transition: max-height .3s ease, padding .3s ease;
}

.faq-item.active .faq-answer {
  max-height: 240px;
  padding: 0 24px 22px;
}

.faq-answer p {
  margin: 0;
}

/* footer */
.footer {
  background: var(--dark);
  color: #fff;
  padding: 66px 0 26px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr 1fr;
  gap: 30px;
  margin-bottom: 28px;
}

.footer-brand {
  margin-bottom: 16px;
}

.footer-text,
.footer-bottom p {
  color: rgba(255,255,255,0.62);
}

.footer h3 {
  margin: 0 0 16px;
  font-size: 1.08rem;
}

.footer-links {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.footer-links a {
  color: rgba(255,255,255,0.72);
  transition: var(--transition);
}

.footer-links a:hover {
  color: #fff;
}

.footer-bottom {
  border-top: 1px solid rgba(255,255,255,0.08);
  padding-top: 22px;
}

/* animation */
.animate {
  opacity: 0;
  transform: translateY(26px);
}

.animate.show {
  opacity: 1;
  transform: translateY(0);
  transition: opacity .55s ease, transform .55s ease;
}

/* device tip */
.device-tip {
  position: fixed;
  right: 20px;
  bottom: 20px;
  z-index: 1000;
  max-width: 300px;
  padding: 15px 22px;
  border-radius: 14px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: #fff;
  box-shadow: 0 18px 34px rgba(0,102,255,0.24);
  cursor: pointer;
  opacity: 0;
  transform: translateY(12px);
  transition: opacity .3s ease, transform .3s ease;
}

.device-tip.show {
  opacity: 1;
  transform: translateY(0);
}

/* responsive */
@media (max-width: 992px) {
  .hero-inner,
  .feature-grid,
  .promise-grid,
  .guide-grid,
  .footer-grid,
  .download-grid,
  .stats-grid {
    grid-template-columns: 1fr 1fr;
  }

  .hero-inner {
    align-items: start;
  }

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

@media (max-width: 768px) {
  .nav {
    position: absolute;
    top: 74px;
    left: 0;
    right: 0;
    background: rgba(255,255,255,0.98);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid rgba(0,0,0,0.05);
    display: none;
    flex-direction: column;
    align-items: flex-start;
    gap: 0;
    padding: 12px 20px 18px;
  }

  .nav.open {
    display: flex;
  }

  .nav-link {
    width: 100%;
    padding: 12px 0;
  }

  .menu-btn {
    display: inline-flex;
  }

  .hero-inner,
  .download-grid,
  .feature-grid,
  .promise-grid,
  .guide-grid,
  .stats-grid,
  .footer-grid {
    grid-template-columns: 1fr;
  }

  .hero {
    padding: 80px 0 56px;
  }

  .hero-desc {
    font-size: 1rem;
  }

  .hero-actions {
    flex-direction: column;
  }

  .btn {
    width: 100%;
  }

  .faq-question {
    padding: 18px 18px;
    font-size: 0.96rem;
  }

  .faq-answer {
    padding: 0 18px;
  }

  .faq-item.active .faq-answer {
    padding: 0 18px 18px;
  }

  .device-tip {
    left: 16px;
    right: 16px;
    max-width: none;
  }
}