:root {
  --paper: #f6f3ee;
  --ink: #241c15;
  --muted: #756b61;
  --line: #ddd3c7;
  --accent: #2b2118;
  --danger: #a32f2f;
}

* { box-sizing: border-box; }
body {
  margin: 0;
  min-height: 100dvh;
  background: var(--paper);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Microsoft JhengHei", "Noto Sans TC", sans-serif;
}
.auth-shell { padding: max(24px, env(safe-area-inset-top)) 0 max(24px, env(safe-area-inset-bottom)); }
.auth-card {
  width: min(calc(100% - 32px), 420px);
  margin: clamp(48px, 12vh, 120px) auto;
  padding: 28px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 18px;
  box-shadow: 0 18px 45px rgba(50, 36, 22, .08);
}
.eyebrow { margin: 0 0 8px; color: var(--muted); font-size: 14px; letter-spacing: .08em; }
h1 { margin: 0 0 10px; font-size: clamp(25px, 7vw, 32px); letter-spacing: .02em; }
.intro, .help { color: var(--muted); line-height: 1.7; }
.help { margin: 22px 0 0; font-size: 14px; text-align: center; }
label { display: block; margin: 18px 0 7px; font-weight: 700; }
input, button {
  width: 100%;
  min-height: 52px;
  border-radius: 12px;
  font: inherit;
  font-size: 17px;
}
input { border: 1px solid var(--line); padding: 12px 14px; color: var(--ink); background: #fff; }
input:focus { outline: 3px solid rgba(43, 33, 24, .13); border-color: var(--accent); }
button { margin-top: 22px; border: 0; padding: 12px 16px; background: var(--accent); color: #fff; font-weight: 700; cursor: pointer; }
button:disabled { cursor: wait; opacity: .58; }
.secondary { background: transparent; border: 1px solid var(--line); color: var(--ink); }
.alert { min-height: 24px; margin: 14px 0 -5px; color: var(--danger); line-height: 1.5; }
.account { margin: 18px 0; padding: 14px; border: 1px solid var(--line); border-radius: 12px; background: var(--paper); }

@media (max-width: 640px) {
  .auth-shell { padding-top: 20px; }
  .auth-card { margin: 20px auto; padding: 24px 20px; border-radius: 16px; }
}