/* D9 Official Site — inspired by mobile app download landings */

:root {
  --d9-blue: #1478ff;
  --d9-blue-deep: #165dce;
  --d9-blue-glow: rgba(20, 120, 255, 0.45);
  --bg-deep: #081426;
  --bg-mid: #0d2345;
  --bg-card: rgba(13, 35, 69, 0.72);
  --text-primary: #f4f8ff;
  --text-secondary: #9eb4d8;
  --text-muted: #6b86ad;
  --border: rgba(120, 160, 220, 0.18);
  --success: #22c55e;
  --radius-lg: 24px;
  --radius-md: 16px;
  --shadow: 0 24px 80px rgba(0, 0, 0, 0.35);
  --font: "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font);
  color: var(--text-primary);
  background:
    radial-gradient(ellipse 80% 60% at 50% -10%, rgba(20, 120, 255, 0.28), transparent 60%),
    radial-gradient(circle at 90% 20%, rgba(22, 93, 206, 0.18), transparent 35%),
    linear-gradient(180deg, var(--bg-deep) 0%, var(--bg-mid) 45%, #0a1a33 100%);
  line-height: 1.6;
}

a {
  color: var(--d9-blue);
  text-decoration: none;
}

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

.container {
  width: min(1120px, calc(100% - 32px));
  margin: 0 auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  backdrop-filter: blur(16px);
  background: rgba(8, 20, 38, 0.82);
  border-bottom: 1px solid var(--border);
}

.site-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 64px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  color: inherit;
}

.brand__logo {
  width: 40px;
  height: 40px;
  border-radius: 12px;
  box-shadow: 0 8px 24px var(--d9-blue-glow);
}

.brand__name {
  font-size: 18px;
  font-weight: 700;
  letter-spacing: 0.02em;
}

.nav-actions {
  display: flex;
  gap: 10px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-height: 46px;
  padding: 0 20px;
  border-radius: 999px;
  border: 1px solid transparent;
  font: inherit;
  font-weight: 650;
  cursor: pointer;
  transition: transform 0.15s ease, box-shadow 0.15s ease, opacity 0.15s ease;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn:active {
  transform: translateY(0);
}

.btn--primary {
  color: #fff;
  background: linear-gradient(135deg, var(--d9-blue), var(--d9-blue-deep));
  box-shadow: 0 10px 30px var(--d9-blue-glow);
}

.btn--ghost {
  color: var(--text-primary);
  background: rgba(255, 255, 255, 0.04);
  border-color: var(--border);
}

.btn--android {
  background: linear-gradient(135deg, #34d399, #059669);
  color: #fff;
  box-shadow: 0 10px 30px rgba(52, 211, 153, 0.25);
}

.btn--ios {
  background: linear-gradient(135deg, #60a5fa, #2563eb);
  color: #fff;
  box-shadow: 0 10px 30px rgba(37, 99, 235, 0.25);
}

.btn--lg {
  min-height: 56px;
  width: 100%;
  font-size: 17px;
}

.btn[disabled] {
  opacity: 0.45;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.hero {
  padding: 56px 0 40px;
  text-align: center;
}

.hero__badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 14px;
  border-radius: 999px;
  background: rgba(20, 120, 255, 0.12);
  border: 1px solid rgba(20, 120, 255, 0.25);
  color: #b9d6ff;
  font-size: 13px;
  margin-bottom: 24px;
}

.hero__icon-wrap {
  position: relative;
  width: 120px;
  height: 120px;
  margin: 0 auto 24px;
}

.hero__icon {
  width: 120px;
  height: 120px;
  border-radius: 28px;
  box-shadow: var(--shadow), 0 0 0 1px rgba(255, 255, 255, 0.08);
}

.hero__icon-glow {
  position: absolute;
  inset: -20px;
  background: radial-gradient(circle, var(--d9-blue-glow), transparent 70%);
  z-index: -1;
}

.hero h1 {
  margin: 0 0 10px;
  font-size: clamp(32px, 6vw, 48px);
  line-height: 1.15;
  letter-spacing: -0.02em;
}

.hero__slogan {
  margin: 0 0 28px;
  color: var(--text-secondary);
  font-size: clamp(16px, 3vw, 20px);
}

.hero__stats {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 16px;
  margin-bottom: 32px;
}

.stat-pill {
  min-width: 120px;
  padding: 14px 18px;
  border-radius: var(--radius-md);
  background: var(--bg-card);
  border: 1px solid var(--border);
}

.stat-pill__label {
  display: block;
  font-size: 12px;
  color: var(--text-muted);
  margin-bottom: 4px;
}

.stat-pill__value {
  font-size: 16px;
  font-weight: 700;
}

.download-card {
  max-width: 520px;
  margin: 0 auto 48px;
  padding: 28px 24px;
  border-radius: var(--radius-lg);
  background: var(--bg-card);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
  backdrop-filter: blur(12px);
}

.download-card__title {
  margin: 0 0 8px;
  font-size: 20px;
}

.download-card__hint {
  margin: 0 0 20px;
  color: var(--text-secondary);
  font-size: 14px;
}

.download-grid {
  display: grid;
  gap: 12px;
}

.download-note {
  margin-top: 16px;
  padding: 12px 14px;
  border-radius: 12px;
  background: rgba(20, 120, 255, 0.08);
  border: 1px solid rgba(20, 120, 255, 0.18);
  color: var(--text-secondary);
  font-size: 13px;
  text-align: left;
}

.section {
  padding: 24px 0 56px;
}

.section__title {
  margin: 0 0 8px;
  font-size: 28px;
  text-align: center;
}

.section__subtitle {
  margin: 0 auto 32px;
  max-width: 560px;
  text-align: center;
  color: var(--text-secondary);
}

.features {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 16px;
}

.feature-card {
  padding: 22px;
  border-radius: var(--radius-md);
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--border);
}

.feature-card__icon {
  width: 44px;
  height: 44px;
  display: grid;
  place-items: center;
  border-radius: 12px;
  background: rgba(20, 120, 255, 0.15);
  font-size: 22px;
  margin-bottom: 14px;
}

.feature-card h3 {
  margin: 0 0 8px;
  font-size: 17px;
}

.feature-card p {
  margin: 0;
  color: var(--text-secondary);
  font-size: 14px;
}

.guide-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 16px;
}

.guide-card {
  border-radius: var(--radius-md);
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--border);
  overflow: hidden;
}

.guide-card__head {
  padding: 18px 20px;
  font-weight: 700;
  background: rgba(20, 120, 255, 0.08);
  border-bottom: 1px solid var(--border);
}

.guide-card ol {
  margin: 0;
  padding: 18px 20px 18px 36px;
  color: var(--text-secondary);
  font-size: 14px;
}

.guide-card li + li {
  margin-top: 10px;
}

.faq {
  max-width: 760px;
  margin: 0 auto;
}

.faq details {
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: rgba(255, 255, 255, 0.03);
  padding: 16px 18px;
}

.faq details + details {
  margin-top: 12px;
}

.faq summary {
  cursor: pointer;
  font-weight: 650;
}

.faq p {
  margin: 12px 0 0;
  color: var(--text-secondary);
  font-size: 14px;
}

.site-footer {
  padding: 32px 0 48px;
  border-top: 1px solid var(--border);
  text-align: center;
  color: var(--text-muted);
  font-size: 13px;
}

.site-footer__links {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 16px;
  margin-bottom: 12px;
}

.qr-panel {
  display: none;
  margin-top: 20px;
  padding-top: 20px;
  border-top: 1px dashed var(--border);
  text-align: center;
}

.qr-panel.is-visible {
  display: block;
}

.qr-panel canvas {
  margin: 0 auto 10px;
  border-radius: 12px;
  background: #fff;
  padding: 8px;
}

@media (min-width: 768px) {
  .hero {
    padding-top: 72px;
  }

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

  .btn--lg {
    width: auto;
    min-width: 220px;
  }
}

@media (max-width: 640px) {
  .nav-actions .btn--ghost {
    display: none;
  }
}