* {
  box-sizing: border-box;
}

body {
  background: #f1f1f1;
  font-family: Arial, sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.container {
  background: white;
  padding: 30px;
  width: 100%;
  max-width: 400px;
  border-radius: 8px;
  box-shadow: 0 0 10px rgba(0,0,0,0.1);
}

h2 {
  text-align: center;
  margin-bottom: 20px;
}

.input-group {
  margin-bottom: 15px;
  position: relative;
}

input {
  width: 100%;
  padding: 10px;
  border: 2px solid #ddd;
  border-radius: 4px;
  outline: none;
}

input:focus {
  border-color: #777;
}

small {
  color: red;
  visibility: hidden;
  position: absolute;
  bottom: -18px;
  left: 0;
  font-size: 12px;
}

button {
  width: 100%;
  padding: 12px;
  background: #007bff;
  color: white;
  border: none;
  border-radius: 4px;
  font-size: 16px;
  cursor: pointer;
}

.input-group.error input {
  border-color: red;
}

.input-group.success input {
  border-color: green;
}

.input-group.error small {
  visibility: visible;
}