:root {
  --bg: #f5f7fa;
  --card: #ffffff;
  --line: #e4e8ef;
  --ink: #1f2733;
  --mut: #6b7480;
  --brand: #2f6fed;
  --brand-soft: #eaf1fe;
  --ok: #2e9e5b;
  --warn: #c0392b;
}
* { box-sizing: border-box; }
body {
  margin: 0; font-family: -apple-system, "Segoe UI", Roboto, "PingFang SC", "Microsoft YaHei", sans-serif;
  background: var(--bg); color: var(--ink); line-height: 1.65;
}
a { color: inherit; text-decoration: none; }

.topbar { display: flex; align-items: center; justify-content: space-between; padding: 16px 28px; border-bottom: 1px solid var(--line); background: var(--card); position: sticky; top: 0; z-index: 10; }
.brand { font-weight: 700; font-size: 18px; }
.brand__sub { font-size: 11px; color: var(--mut); font-weight: 500; margin-left: 6px; letter-spacing: 1px; }
.nav { display: flex; gap: 18px; font-size: 14px; color: var(--mut); }
.nav a:hover { color: var(--brand); }

.wrap { max-width: 920px; margin: 0 auto; padding: 0 20px 40px; }

.hero { text-align: center; padding: 54px 20px 36px; }
.hero h1 { font-size: 36px; margin: 0 0 14px; font-weight: 700; letter-spacing: -0.5px; }
.hero__sub { color: var(--mut); max-width: 600px; margin: 0 auto 26px; font-size: 15px; }
.hero__sub strong { color: var(--ink); }
.hero__cta { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.hero__meta { margin-top: 18px; font-size: 13px; color: var(--mut); }

.btn { display: inline-block; background: #fff; color: var(--ink); border: 1px solid var(--line); padding: 11px 22px; border-radius: 10px; font-size: 14px; font-weight: 500; cursor: pointer; }
.btn:hover { border-color: var(--brand); color: var(--brand); }
.btn--primary { background: var(--brand); color: #fff; border-color: var(--brand); }
.btn--primary:hover { opacity: .92; color: #fff; }
.btn:disabled { opacity: .6; cursor: default; }

.usecases { padding: 20px 0; }
.usecases h2 { font-size: 19px; text-align: center; margin: 10px 0 22px; }
.cards { display: grid; grid-template-columns: repeat(2, 1fr); gap: 14px; }
.card { background: var(--card); border: 1px solid var(--line); border-radius: 14px; padding: 18px 20px; }
.card__icon { font-size: 26px; }
.card h3 { margin: 8px 0 6px; font-size: 15px; }
.card p { margin: 0; color: var(--mut); font-size: 13px; }

.panel { background: var(--card); border: 1px solid var(--line); border-radius: 16px; padding: 24px; margin: 22px 0; }
.panel h2 { margin: 0 0 18px; font-size: 18px; }
.panel h3 { margin: 26px 0 12px; font-size: 15px; color: var(--mut); }

.form { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
.field { display: flex; flex-direction: column; gap: 6px; font-size: 13px; color: var(--mut); }
.field--wide { grid-column: 1 / -1; }
.field input, .field select { padding: 10px 12px; border: 1px solid var(--line); border-radius: 8px; font-size: 14px; color: var(--ink); background: #fff; }
.field input:focus, .field select:focus { outline: none; border-color: var(--brand); }
.form__actions { grid-column: 1 / -1; display: flex; align-items: center; gap: 14px; }
.form__msg { font-size: 13px; min-height: 18px; }

.list { display: flex; flex-direction: column; gap: 10px; }
.empty { color: var(--mut); font-size: 14px; padding: 12px 0; }
.row { border: 1px solid var(--line); border-radius: 10px; padding: 12px 14px; font-size: 13px; display: flex; flex-direction: column; gap: 4px; }
.row__main { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.row__main a { color: var(--brand); word-break: break-all; }
.row__tag { font-size: 11px; padding: 1px 8px; border-radius: 10px; background: var(--brand-soft); color: var(--brand); }
.row__meta { color: var(--mut); font-size: 12px; }

.pro { border-color: var(--brand); box-shadow: 0 0 0 3px var(--brand-soft); }
.pro__list { list-style: none; padding: 0; margin: 0 0 18px; }
.pro__list li { padding: 7px 0 7px 24px; position: relative; font-size: 14px; border-bottom: 1px dashed var(--line); }
.pro__list li::before { content: "✓"; color: var(--ok); position: absolute; left: 0; font-weight: 700; }
.pro__email { padding: 10px 12px; border: 1px solid var(--line); border-radius: 8px; font-size: 14px; min-width: 220px; }
.pro__note { color: var(--mut); font-size: 12px; margin: 14px 0 0; }

/* 收款码区 */
.pay { margin: 6px 0 18px; padding: 16px; background: var(--brand-soft); border: 1px solid var(--line); border-radius: 12px; }
.pay__title { font-weight: 600; margin: 0 0 12px; font-size: 15px; }
.pay__qrs { display: flex; gap: 24px; flex-wrap: wrap; }
.pay__qr { display: flex; flex-direction: column; align-items: center; gap: 8px; font-size: 13px; color: var(--mut); }
.pay__qr-img { width: 160px; height: 160px; background: var(--card); border: 1px solid var(--line); border-radius: 10px; display: flex; align-items: center; justify-content: center; overflow: hidden; }
.pay__qr-img img { width: 100%; height: 100%; object-fit: contain; }
.qr-ph { color: var(--mut); font-size: 13px; text-align: center; line-height: 1.5; padding: 8px; }
.pay__hint { font-size: 12px; color: var(--mut); margin: 12px 0 0; }
.pay__form { margin-top: 14px; }

.footer { text-align: center; color: var(--mut); font-size: 12px; padding: 30px 20px 50px; border-top: 1px solid var(--line); margin-top: 20px; }

@media (max-width: 640px) {
  .cards { grid-template-columns: 1fr; }
  .form { grid-template-columns: 1fr; }
  .hero h1 { font-size: 28px; }
}