:root {
  --accent: #136f8f;
  --muted: #6b7280;
  --card: #ffffff;
  --bg: #f6f9fb;
  --max-width: 1000px;
}

* { box-sizing: border-box; }

body {
  min-height: 100vh;
  display: flex;
  margin: 0;
  padding: 2.25rem;
  background: var(--bg);
  color: #0f172a;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

.container { width: 100%; max-width: var(--max-width); margin: 0 auto; display: flex; flex-direction: column; }
header { margin-bottom: 1.5rem; }
h1 { margin: 0 0 .5rem; }
a { color: var(--accent); }
a:focus-visible { outline: 3px solid var(--accent); outline-offset: 4px; }

.info-card,
.card {
  background: var(--card);
  border-radius: 10px;
  box-shadow: 0 6px 18px rgba(16,24,40,0.06);
}

.info-card { padding: 1.5rem; }
.info-card + .info-card { margin-top: 1.5rem; }
.info-card h2 { margin: 0 0 1rem; color: var(--accent); font-size: 1.2rem; }
.info-card p { margin: 0 0 1rem; color: var(--muted); line-height: 1.6; }
.info-card p:last-child { margin-bottom: 0; }
.introduction { margin-bottom: 1.5rem; }
.demo-action { text-align: center; }
.card-row { display: flex; gap: 1rem; margin-bottom: 1.5rem; }

.card {
  flex: 1;
  min-width: 0;
  padding: 1.25rem;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-start;
  transition: transform .15s ease, box-shadow .15s ease;
}

.card:hover,
.card:focus-within {
  transform: translateY(-6px);
  box-shadow: 0 12px 30px rgba(16,24,40,0.08);
}

.card-title { margin: 0; font-size: 1.1rem; color: var(--accent); font-weight: bold; }
.card p { margin: .5rem 0 0; color: var(--muted); font-size: .95rem; text-align: left; }
.card-video { display: block; width: 100%; margin-top: 1rem; border-radius: 6px; }
.video-wrap { width: 100%; margin-top: 1rem; border-radius: 8px; overflow: hidden; box-shadow: 0 8px 20px rgba(2,6,23,0.06); }
.responsive-iframe { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; }
.responsive-iframe iframe { position: absolute; top: 0; left: 0; width: 100%; height: 100%; border: 0; }
.btn {
  display: inline-block;
  margin-top: 1rem;
  padding: .45rem .9rem;
  border-radius: 6px;
  background: var(--accent);
  color: #fff;
  text-decoration: none;
}

footer { padding-top: 1.5rem; font-size: .85rem; text-align: center; }
.version-footer { margin-top: auto; color: var(--muted); }

@media (max-width: 720px) {
  body { padding: 1rem; }
  .card-row { flex-direction: column; }
  .card { flex: none; width: 100%; min-width: 0; }
}

@media (prefers-reduced-motion: reduce) {
  .card { transition: none; }
  .card:hover,
  .card:focus-within { transform: none; }
}