body {
  font-family: Arial, sans-serif;
  background: #f4f6f8;
  margin: 0;
}

header {
  background: #1f2937;
  color: #fff;
  padding: 20px;
  text-align: center;
}

.container {
  max-width: 900px;
  background: #fff;
  margin: 30px auto;
  padding: 25px;
  border-radius: 6px;
}

.btn {
  display: inline-block;
  padding: 12px 20px;
  background: #2563eb;
  color: #fff;
  text-decoration: none;
  border-radius: 4px;
}

input {
  padding: 10px;
  width: 100%;
  margin-bottom: 15px;
}

.warning {
  color: red;
  font-weight: bold;
}

footer {
  text-align: center;
  padding: 15px;
  background: #e5e7eb;
}