:root {
  --bg: #f3f4f6;
  --card: #ffffff;
  --text: #111827;
  --muted: #6b7280;
  --border: #d1d5db;
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --error: #b91c1c;
  --error-bg: #fef2f2;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f172a;
    --card: #1e293b;
    --text: #e5e7eb;
    --muted: #94a3b8;
    --border: #334155;
    --error: #fca5a5;
    --error-bg: #450a0a;
  }
}
* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
  background: var(--bg);
  color: var(--text);
  font: 15px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}
.card {
  width: 100%;
  max-width: 360px;
  padding: 32px 28px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, .06);
}
.brand { display: flex; align-items: center; gap: 10px; color: var(--muted); font-weight: 500; }
h1 { margin: 20px 0 16px; font-size: 22px; font-weight: 600; }
form { display: flex; flex-direction: column; }
label { margin: 10px 0 4px; font-size: 13px; color: var(--muted); }
input[type=text], input[type=password] {
  padding: 9px 11px;
  font: inherit;
  color: var(--text);
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 8px;
  outline: none;
}
input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px rgba(37, 99, 235, .2); }
input[aria-invalid=true] { border-color: var(--error); }
.remember { display: flex; align-items: center; gap: 8px; margin-top: 14px; font-size: 14px; color: var(--text); }
.error { margin: 14px 0 0; padding: 8px 10px; font-size: 14px; color: var(--error); background: var(--error-bg); border-radius: 8px; }
button {
  margin-top: 18px;
  padding: 10px;
  font: inherit;
  font-weight: 600;
  color: #fff;
  background: var(--accent);
  border: 0;
  border-radius: 8px;
  cursor: pointer;
}
button:hover { background: var(--accent-hover); }
button:disabled { opacity: .6; cursor: progress; }
.hint { margin: 18px 0 0; font-size: 13px; color: var(--muted); text-align: center; }