:root {
  --bg: #f4f6f2;
  --surface: #ffffff;
  --text: #1f2933;
  --muted: #5f6b76;
  --border: #dfe5df;
  --accent: #245f4f;
  --notice: #eef4ef;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.55;
}

header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}

header .inner,
main,
footer {
  width: min(100% - 32px, 980px);
  margin: 0 auto;
}

header .inner { padding: 28px 0 24px; }

h1, h2, h3 { line-height: 1.2; }

h1 { margin: 0 0 10px; font-size: clamp(1.8rem, 5vw, 2.55rem); }
h2 { margin: 30px 0 14px; font-size: 1.35rem; }
h3 { margin: 0 0 8px; font-size: 1.18rem; }

a { color: var(--accent); }

.intro, .meta {
  color: var(--muted);
}

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

main { padding: 24px 0 38px; }

.notice {
  background: var(--notice);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px 16px;
  margin: 0 0 24px;
}

.grid {
  display: grid;
  gap: 22px;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  overflow: hidden;
  box-shadow: 0 1px 2px rgba(0,0,0,.04);
}

.card > .content { padding: 16px; }

.card video,
.card iframe {
  max-width: 100%;
}

.instructions {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px 18px;
  margin-bottom: 18px;
}

.instructions ol { margin: 0; padding-left: 1.25rem; }
.instructions li + li { margin-top: 8px; }

.button {
  display: inline-block;
  padding: 9px 14px;
  border-radius: 9px;
  background: var(--accent);
  color: white;
  text-decoration: none;
  font-weight: 600;
}

.video-container {
  width: min(100%, 720px);
  aspect-ratio: 16 / 9;
  margin: 18px auto;
  background: #000;
  border-radius: 12px;
  overflow: hidden;
}

.video-container iframe {
  width: 100%;
  height: 100%;
  border: 0;
  display: block;
}

footer {
  color: var(--muted);
  border-top: 1px solid var(--border);
  padding: 22px 0 34px;
  font-size: .94rem;
}

@media (max-width: 560px) {
  header .inner, main, footer { width: min(100% - 22px, 980px); }
  .grid { grid-template-columns: 1fr; }
}