:root {
  --bg: #f4f5f7;
  --card: #ffffff;
  --text: #171717;
  --muted: #616161;
  --line: #d9d9d9;
  --danger: #d62828;
  --accent: #111111;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  background: radial-gradient(circle at top, #ffffff 0%, var(--bg) 55%);
  color: var(--text);
}

.login-shell {
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 20px;
}

.login-card {
  width: 100%;
  max-width: 420px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 26px;
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.06);
}

h1 {
  margin: 0;
  font-size: 24px;
}

.sub {
  margin: 8px 0 18px;
  color: var(--muted);
}

.alert {
  margin-bottom: 10px;
  padding: 10px 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fafafa;
}

.alert.error {
  border-color: #f5b9b9;
  color: var(--danger);
  background: #fff4f4;
}

label {
  display: block;
  font-size: 14px;
  margin-top: 12px;
  margin-bottom: 6px;
}

input {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 10px 12px;
  font-size: 14px;
}

input:focus {
  outline: 2px solid #d0d0d0;
  outline-offset: 1px;
}

.field-error {
  margin-top: 4px;
  color: var(--danger);
  font-size: 12px;
}

button {
  width: 100%;
  margin-top: 18px;
  border: 0;
  border-radius: 10px;
  background: var(--accent);
  color: #fff;
  padding: 11px 12px;
  font-size: 15px;
  cursor: pointer;
}

button:hover {
  opacity: 0.92;
}

@media (max-width: 720px) {
  .login-shell {
    place-items: start;
    padding: 16px;
    padding-top: max(16px, env(safe-area-inset-top));
  }

  .login-card {
    max-width: none;
    border-radius: 12px;
    padding: 18px 16px;
    box-shadow: 0 8px 22px rgba(0, 0, 0, 0.05);
  }

  h1 {
    font-size: 22px;
  }

  .sub {
    margin-bottom: 14px;
    font-size: 14px;
  }

  label {
    font-size: 13px;
    margin-top: 10px;
  }

  input,
  button {
    min-height: 44px;
    font-size: 16px;
  }
}

@media (max-width: 420px) {
  .login-shell {
    padding: 12px;
  }

  .login-card {
    padding: 16px 14px;
  }
}