:root {
  --ink: #101820;
  --white: #ffffff;
  --blue: #4f9ec9;
  --blue-soft: #eff8fd;
  --blue-line: #c7dfed;
  --danger: #a12d2d;
}

* { box-sizing: border-box; }

body {
  min-height: 100vh;
  margin: 0;
  background: var(--white);
  color: var(--ink);
  font-family: "Noto Sans TC", "Microsoft JhengHei", sans-serif;
  font-size: 16px;
  line-height: 1.8;
}

.top-line {
  height: 60px;
  border-bottom: 1px solid var(--blue-line);
  box-shadow: inset 0 -3px 0 var(--blue);
}

main {
  min-height: calc(100vh - 60px);
  display: grid;
  place-items: center;
  padding: 80px;
}

.login-card {
  width: min(520px, 100%);
  padding: 42px;
  border: 1px solid var(--blue-line);
  border-top: 4px solid var(--blue);
  background: var(--white);
  box-shadow: 0 12px 30px rgba(22, 58, 77, 0.09);
}

.eyebrow {
  margin: 0 0 4px;
  font-weight: 700;
  letter-spacing: 0.08em;
}

h1 {
  margin: 0;
  font-size: 42px;
  line-height: 1.35;
}

.description { margin: 16px 0 28px; }

form { display: grid; gap: 10px; }
label { font-weight: 700; }

input {
  width: 100%;
  min-height: 48px;
  padding: 9px 12px;
  border: 1px solid #8ebdd7;
  color: var(--ink);
  font: inherit;
}

input:focus-visible,
button:focus-visible {
  outline: 3px solid rgba(79, 158, 201, 0.35);
  outline-offset: 2px;
}

button {
  min-height: 46px;
  margin-top: 10px;
  border: 1px solid var(--ink);
  background: var(--ink);
  color: var(--white);
  cursor: pointer;
  font: inherit;
  font-weight: 700;
}

button:hover { background: #263746; }
button:disabled { cursor: wait; opacity: 0.7; }

.error {
  margin: 4px 0 0;
  padding: 8px 10px;
  border: 1px solid #e5bcbc;
  background: #fff5f5;
  color: var(--danger);
}

.hidden { display: none; }

@media (max-width: 680px) {
  main { padding: 24px; }
  .login-card { padding: 28px; }
  h1 { font-size: 34px; }
}