:root {
  --primary: #4F46E5;
  --primary-dark: #4338CA;
  --tertiary: #7C3AED;
  --primary-container: #E0E7FF;
  --background: #E4E1F2;
  --surface: #FFFFFF;
  --on-surface: #1A1B25;
  --on-surface-variant: #47455A;
  --outline: #C5C4D3;
  --error: #BA1A1A;
  --radius-lg: 24px;
  --radius-md: 16px;
  --shadow: 0 10px 30px rgba(79, 70, 229, 0.12);
  --shadow-lg: 0 20px 50px rgba(79, 70, 229, 0.18);
}

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

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Inter", "Helvetica Neue", Arial, sans-serif;
  color: var(--on-surface);
  background: var(--background);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

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

/* Top bar */
.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 14px 24px;
  background: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--outline);
}
.brand { display: flex; align-items: center; gap: 10px; color: var(--on-surface); font-weight: 700; font-size: 18px; }
.brand img { border-radius: 10px; }
.nav { display: flex; gap: 20px; }
.nav a { color: var(--on-surface-variant); font-weight: 500; }
.nav a:hover { color: var(--primary); }

/* Hero */
.hero {
  text-align: center;
  padding: 72px 24px 56px;
  background:
    radial-gradient(ellipse at top, rgba(124, 58, 237, 0.14), transparent 55%),
    linear-gradient(180deg, #EDEBF7 0%, var(--background) 100%);
}
.hero-logo {
  width: 96px;
  height: 96px;
  border-radius: 24px;
  box-shadow: var(--shadow-lg);
  margin-bottom: 24px;
}
.hero h1 {
  font-size: clamp(30px, 6vw, 52px);
  letter-spacing: -0.02em;
  background: linear-gradient(120deg, var(--primary), var(--tertiary));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: 12px;
}
.tagline { color: var(--on-surface-variant); font-size: clamp(16px, 2.4vw, 20px); margin-bottom: 28px; }
.hero-actions { display: flex; gap: 14px; justify-content: center; flex-wrap: wrap; }

/* Buttons */
.btn {
  display: inline-block;
  padding: 13px 26px;
  border-radius: 999px;
  font-weight: 600;
  font-size: 16px;
  transition: transform 0.15s ease, box-shadow 0.15s ease, background 0.15s ease;
}
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--primary); color: #fff; box-shadow: var(--shadow); }
.btn-primary:hover { background: var(--primary-dark); box-shadow: var(--shadow-lg); transform: translateY(-1px); }
.btn-ghost { color: var(--primary); background: var(--surface); border: 1px solid var(--primary-container); }
.btn-ghost:hover { background: var(--primary-container); }
.btn-lg { padding: 16px 40px; font-size: 18px; }

/* Sections */
.section { padding: 64px 24px; max-width: 1040px; margin: 0 auto; }
.section h2 { font-size: clamp(24px, 4vw, 34px); text-align: center; letter-spacing: -0.01em; margin-bottom: 8px; }
.section-sub { text-align: center; color: var(--on-surface-variant); margin-bottom: 40px; }

/* Feature cards */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
}
.card {
  background: var(--surface);
  border-radius: var(--radius-lg);
  padding: 28px 24px;
  box-shadow: var(--shadow);
  transition: transform 0.18s ease, box-shadow 0.18s ease;
}
.card:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.card-icon { font-size: 34px; margin-bottom: 14px; }
.card h3 { font-size: 19px; margin-bottom: 8px; }
.card p { color: var(--on-surface-variant); font-size: 15px; }

/* Download */
.download { padding-top: 20px; }
.download-card {
  background: linear-gradient(135deg, var(--primary) 0%, var(--tertiary) 100%);
  color: #fff;
  border-radius: var(--radius-lg);
  padding: 48px 32px;
  text-align: center;
  box-shadow: var(--shadow-lg);
}
.download-card .section-sub { color: rgba(255, 255, 255, 0.85); }
.version { margin: 6px 0 24px; color: rgba(255, 255, 255, 0.9); }
.version strong { font-size: 20px; }
.download-card .btn-primary { background: #fff; color: var(--primary); box-shadow: 0 10px 24px rgba(0, 0, 0, 0.18); }
.download-card .btn-primary:hover { background: var(--primary-container); }
.download-note { margin-top: 18px; font-size: 13px; color: rgba(255, 255, 255, 0.75); }

/* Footer */
.footer {
  text-align: center;
  padding: 32px 24px;
  color: var(--on-surface-variant);
  font-size: 14px;
  border-top: 1px solid var(--outline);
}
.footer a { font-weight: 500; }

/* Responsive */
@media (max-width: 560px) {
  .topbar { padding: 12px 16px; }
  .brand { font-size: 16px; }
  .nav { gap: 14px; }
  .hero { padding: 56px 16px 44px; }
  .section { padding: 48px 16px; }
}