body {
  margin: 0;
  font-family: "Noto Sans TC", Arial, sans-serif;
  background: #f4f6f8;
  color: #003366;
}

header {
  background: #005bac;
  color: white;
  padding: 20px;
  text-align: center;
  font-size: 32px;
  font-weight: bold;
}

.container {
  padding: 30px;
  max-width: 900px;
  margin: auto;
}

button {
  font-size: 28px;
  padding: 25px;
  margin: 15px;
  width: 250px;
  border-radius: 12px;
  border: none;
  cursor: pointer;
  border: 1px solid saddlebrown;
}

.btn-a { background: #1e90ff; color: white; }
.btn-b { background: #28a745; color: white; }
.btn-c { background: #ff9800; color: white; }
.btn-danger { background: #d9534f; color: white; }

.number-box {
  font-size: 64px;
  margin-top: 30px;
  color: #d32f2f;
  font-weight: bold;
}