:root {
  --ink: #081b37;
  --muted: #52667f;
  --blue: #1264e8;
  --line: #d9e3ef;
  --page: #f3f6fa;
}

* { box-sizing: border-box; }

html { background: var(--page); }

body {
  min-height: 100vh;
  margin: 0;
  color: var(--ink);
  background: var(--page);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Microsoft YaHei", Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
}

.page {
  width: min(100%, 820px);
  margin: 0 auto;
  padding: 30px 16px 38px;
}

header { padding: 0 3px 20px; }

h1 {
  margin: 0 0 8px;
  font-size: clamp(30px, 8vw, 42px);
  line-height: 1.15;
}

header p, .tip {
  margin: 0;
  color: var(--muted);
  font-size: 15px;
  line-height: 1.7;
}

.video-list {
  display: grid;
  gap: 18px;
}

.card {
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: #fff;
  box-shadow: 0 12px 30px rgba(8, 27, 55, 0.07);
}

h2 {
  margin: 0 2px 12px;
  font-size: 19px;
  line-height: 1.4;
}

video {
  display: block;
  width: 100%;
  height: clamp(240px, 58vw, 420px);
  border-radius: 9px;
  background: #000;
  object-fit: contain;
}

.tip {
  padding-top: 22px;
  text-align: center;
  font-size: 13px;
}

@media (max-width: 520px) {
  .page { padding: 24px 12px 32px; }
  .card { padding: 12px; }
  video { height: 250px; }
}