:root {
  --primary: #2196F3;
  --primary-dark: #1976D2;
  --primary-darker: #1565C0;
  --primary-tint: #E3F2FD;
  --bg: #f5f7fa;
  --card-bg: #ffffff;
  --text: #1a1a1a;
  --text-muted: #666;
  --border: #e0e0e0;
  --radius: 12px;
  --radius-btn: 8px;
  --shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 8px 24px rgba(33, 150, 243, 0.25);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
               "Helvetica Neue", Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--primary-dark); }

.hero {
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-darker) 100%);
  color: #fff;
  padding: 56px 20px 64px;
  text-align: center;
}
.hero-inner { max-width: 640px; margin: 0 auto; }
.app-icon {
  width: 96px; height: 96px;
  border-radius: 22px;
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.25);
  margin-bottom: 18px;
  background: #fff;
}
.hero h1 {
  font-size: 42px; font-weight: 800; letter-spacing: -0.5px;
  margin: 0;
}
.tagline {
  margin: 8px 0 0; opacity: 0.92; font-size: 16px;
}

.container {
  max-width: 720px;
  margin: -32px auto 32px;
  padding: 0 16px;
  display: flex; flex-direction: column; gap: 16px;
}

.card {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
}

.card h2 {
  margin: 0 0 12px;
  font-size: 20px;
  color: var(--primary-darker);
}
.card h3 { margin: 18px 0 8px; font-size: 16px; }
.card h4 { margin: 0 0 6px; color: var(--primary-dark); font-size: 14px; }

.download-card { text-align: center; }
.version-row {
  display: flex; justify-content: space-between;
  font-size: 14px; color: var(--text-muted);
  padding: 6px 0;
  border-bottom: 1px dashed var(--border);
}
.version-row:nth-of-type(2) { margin-bottom: 18px; border-bottom: none; }
.version-label { font-weight: 600; }
.version-value {
  font-family: ui-monospace, "SF Mono", Menlo, monospace;
  color: var(--text);
}

.btn {
  display: inline-flex;
  align-items: center; justify-content: center;
  gap: 10px;
  padding: 16px 28px;
  border-radius: var(--radius-btn);
  font-size: 17px; font-weight: 700;
  text-decoration: none;
  border: none; cursor: pointer;
  transition: transform 0.08s ease, box-shadow 0.15s ease, background 0.15s ease;
  width: 100%; max-width: 320px;
}
.btn-primary {
  background: var(--primary);
  color: #fff;
  box-shadow: var(--shadow-lg);
}
.btn-primary:hover { background: var(--primary-dark); }
.btn-primary:active { transform: translateY(1px); }
.btn-primary[aria-disabled="true"] {
  background: #b0bec5; box-shadow: none; cursor: not-allowed;
}

.meta { color: var(--text-muted); font-size: 13px; margin: 12px 0 0; }
.error {
  color: #c62828; background: #ffebee;
  padding: 10px 14px; border-radius: 8px;
  font-size: 14px; margin-top: 12px;
}

.steps, .features { padding-left: 22px; margin: 0; }
.steps li, .features li { margin-bottom: 8px; }
.note {
  background: var(--primary-tint);
  color: var(--primary-darker);
  padding: 10px 14px;
  border-radius: 8px;
  font-size: 14px;
  margin-top: 14px;
}

.demo-grid {
  display: grid; grid-template-columns: 1fr 1fr; gap: 16px;
}
.demo-grid code {
  background: #f1f3f5; padding: 2px 6px; border-radius: 4px;
  font-size: 13px;
}

footer {
  text-align: center;
  padding: 28px 16px 40px;
  font-size: 13px; color: var(--text-muted);
}
footer .muted a { color: var(--text-muted); text-decoration: underline; }

@media (max-width: 520px) {
  .hero { padding: 40px 16px 56px; }
  .hero h1 { font-size: 34px; }
  .app-icon { width: 80px; height: 80px; }
  .card { padding: 18px; }
  .demo-grid { grid-template-columns: 1fr; }
}