* { box-sizing: border-box; }
body {
  margin: 0; min-height: 100vh;
  display: flex; align-items: center; justify-content: center;
  background: #f2f4f8;
  font-family: -apple-system, "Segoe UI", "Microsoft YaHei", sans-serif;
  color: #1f2937; padding: 16px;
}
.card {
  background: #fff; width: 100%; max-width: 420px;
  border-radius: 16px; padding: 28px 24px;
  box-shadow: 0 8px 30px rgba(0,0,0,.08); text-align: center;
}
h1 { font-size: 20px; margin: 0 0 16px; }
h2 { font-size: 15px; color: #6b7280; margin: 20px 0 8px; font-weight: 500; }
.muted { color: #6b7280; font-size: 13px; margin: 4px 0; }
.small { font-size: 12px; }
.products { display: flex; flex-direction: column; gap: 10px; }
.product {
  display: flex; justify-content: space-between; align-items: center;
  border: 1.5px solid #e5e7eb; border-radius: 10px; padding: 12px 14px;
  cursor: pointer; transition: .15s;
}
.product.on { border-color: #2563eb; background: #eff6ff; }
.product b { color: #2563eb; }
.channels { display: flex; gap: 12px; justify-content: center; }
.channel {
  border: 1.5px solid #e5e7eb; border-radius: 10px; padding: 10px 16px;
  cursor: pointer; font-size: 14px;
}
.btn {
  display: inline-block; margin-top: 20px; width: 100%;
  background: #2563eb; color: #fff; border: 0; border-radius: 10px;
  padding: 13px; font-size: 16px; cursor: pointer; text-decoration: none;
}
.btn:disabled { background: #9ca3af; cursor: not-allowed; }
.amount { margin: 8px 0; color: #2563eb; }
.amount span { font-size: 40px; font-weight: 700; }
.amount .yuan { font-size: 18px; margin-left: 4px; }
.warn { color: #b45309; font-size: 13px; background: #fffbeb; padding: 8px; border-radius: 8px; }
.qrbox { margin: 16px auto; width: 240px; height: 240px; display: flex; align-items: center; justify-content: center; }
.qrbox img { width: 240px; height: 240px; object-fit: contain; }
.err { color: #dc2626; font-size: 13px; margin-top: 12px; }
.hidden { display: none; }
.okbox .check {
  width: 64px; height: 64px; line-height: 64px; margin: 0 auto 12px;
  border-radius: 50%; background: #16a34a; color: #fff; font-size: 36px;
}
code { background: #f3f4f6; padding: 2px 6px; border-radius: 4px; }