:root {
  --brand: #208aef;
  --brand-strong: #1373d3;
  --brand-soft: #e6f1fc;
  --bg: #ffffff;
  --surface: #f7f9fc;
  --surface-2: #eef3f9;
  --text: #0f172a;
  --text-soft: #4b5563;
  --text-muted: #6b7280;
  --border: #e5e7eb;
  --shadow-sm: 0 1px 2px rgba(15, 23, 42, 0.06);
  --shadow-md: 0 8px 24px rgba(32, 138, 239, 0.12);
  --radius: 16px;
  --radius-sm: 10px;
  --max-w: 1100px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b1220;
    --surface: #111a2e;
    --surface-2: #15203a;
    --text: #e6edf7;
    --text-soft: #c1cbdb;
    --text-muted: #8a97ad;
    --border: #1f2a44;
    --brand-soft: rgba(32, 138, 239, 0.14);
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.4);
    --shadow-md: 0 12px 30px rgba(0, 0, 0, 0.45);
  }
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
}

body {
  font-family:
    -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

a:hover {
  color: var(--brand-strong);
}

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

/* ---------- Top bar ---------- */

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 14px 24px;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(180%) blur(14px);
  -webkit-backdrop-filter: saturate(180%) blur(14px);
  border-bottom: 1px solid var(--border);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 600;
  color: var(--text);
}

.brand img {
  border-radius: 8px;
}

.nav {
  margin-left: auto;
  display: flex;
  gap: 22px;
}

.nav a {
  color: var(--text-soft);
  font-size: 14px;
  font-weight: 500;
}

.nav a:hover {
  color: var(--brand);
}

.lang-toggle {
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text-soft);
  border-radius: 999px;
  padding: 6px 14px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s ease, color 0.15s ease;
}

.lang-toggle:hover {
  background: var(--brand-soft);
  color: var(--brand);
}

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

/* ---------- Hero ---------- */

.hero {
  position: relative;
  text-align: center;
  padding: 96px 24px 80px;
  max-width: var(--max-w);
  margin: 0 auto;
}

.hero-glow {
  position: absolute;
  inset: 0;
  pointer-events: none;
  background:
    radial-gradient(
      circle at 50% 10%,
      color-mix(in srgb, var(--brand) 22%, transparent),
      transparent 60%
    );
  z-index: -1;
}

.hero-logo {
  margin: 0 auto 24px;
  border-radius: 26px;
  box-shadow: var(--shadow-md);
}

.hero-title {
  margin: 0 0 12px;
  font-size: clamp(36px, 6vw, 56px);
  font-weight: 700;
  letter-spacing: -0.02em;
  background: linear-gradient(135deg, var(--brand) 0%, #6cb6ff 100%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.hero-tagline {
  margin: 0 0 8px;
  font-size: clamp(18px, 2.5vw, 22px);
  color: var(--text);
  font-weight: 500;
}

.hero-sub {
  margin: 0 0 32px;
  color: var(--text-muted);
  font-size: 15px;
}

.cta-row {
  display: flex;
  gap: 14px;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 24px;
}

.hero-meta {
  color: var(--text-muted);
  font-size: 13px;
}

/* ---------- Buttons ---------- */

.btn {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  padding: 14px 22px;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: 15px;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform 0.12s ease, box-shadow 0.15s ease,
    background 0.15s ease;
}

.btn span {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  line-height: 1.2;
}

.btn small {
  font-size: 11px;
  font-weight: 500;
  opacity: 0.85;
  letter-spacing: 0.02em;
  text-transform: uppercase;
}

.btn strong {
  font-size: 15px;
  font-weight: 600;
}

.btn-primary {
  background: var(--brand);
  color: #fff;
  box-shadow: var(--shadow-md);
}

.btn-primary:hover {
  background: var(--brand-strong);
  color: #fff;
  transform: translateY(-1px);
}

.btn-secondary {
  background: var(--surface);
  color: var(--text);
  border-color: var(--border);
}

.btn-secondary:hover {
  background: var(--surface-2);
  color: var(--text);
  transform: translateY(-1px);
}

.btn.block {
  width: 100%;
  justify-content: center;
}

/* ---------- Section ---------- */

.section-title {
  text-align: center;
  font-size: clamp(24px, 3.5vw, 32px);
  margin: 0 0 40px;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.features {
  padding: 64px 24px;
  background: var(--surface);
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

.feature-grid {
  display: grid;
  gap: 18px;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  max-width: var(--max-w);
  margin: 0 auto;
}

.feature {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow-sm);
  transition: transform 0.15s ease, box-shadow 0.2s ease;
}

.feature:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.feature-icon {
  font-size: 28px;
  margin-bottom: 8px;
}

.feature h3 {
  margin: 0 0 6px;
  font-size: 17px;
  font-weight: 600;
}

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

/* ---------- Download ---------- */

.download-section {
  padding: 80px 24px;
  max-width: var(--max-w);
  margin: 0 auto;
}

.download-cards {
  display: grid;
  gap: 20px;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.download-card {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  background: var(--bg);
  box-shadow: var(--shadow-sm);
}

.download-card h3 {
  margin: 0 0 8px;
  font-size: 20px;
  font-weight: 700;
}

.download-card > p {
  margin: 0 0 18px;
  color: var(--text-soft);
  font-size: 14px;
}

.hint {
  margin: 14px 0 0;
  font-size: 12px;
  color: var(--text-muted);
}

/* ---------- Footer ---------- */

.footer {
  border-top: 1px solid var(--border);
  background: var(--surface);
  padding: 32px 24px;
}

.footer-inner {
  max-width: var(--max-w);
  margin: 0 auto;
  text-align: center;
  color: var(--text-muted);
  font-size: 13px;
}

.footer-brand {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  color: var(--text);
  font-weight: 600;
  margin-bottom: 8px;
}

.footer-brand img {
  border-radius: 6px;
}

.footer-meta {
  margin: 4px 0;
}

.footer-disclaimer {
  margin: 4px 0 0;
  font-size: 12px;
  opacity: 0.8;
}