html, body { height: 100%; margin: 0; font-family: -apple-system, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif; background: #0e1116; color: #e6edf3; }
body { display: flex; align-items: center; justify-content: center; }
.card { background: #161b22; padding: 32px 28px; border-radius: 10px; width: 320px; box-shadow: 0 8px 30px rgba(0,0,0,.5); border: 1px solid #30363d; }
.card h1 { margin: 0 0 4px; font-size: 22px; }
.card .sub { margin: 0 0 20px; color: #8b949e; font-size: 13px; }
.card input { width: 100%; box-sizing: border-box; padding: 12px 14px; background: #0d1117; border: 1px solid #30363d; color: #e6edf3; border-radius: 6px; font-size: 16px; margin-bottom: 12px; }
.card input:focus { outline: none; border-color: #1f6feb; }
.card button { width: 100%; padding: 10px; background: #238636; color: #fff; border: 0; border-radius: 6px; font-size: 14px; cursor: pointer; }
.card button:hover { background: #2ea043; }
.card .err { color: #f85149; font-size: 13px; margin: 10px 0 0; min-height: 18px; }

@media (max-width: 480px) {
  .card { width: calc(100% - 32px); padding: 28px 22px; }
  .card h1 { font-size: 20px; }
}