body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #f4f7f6;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
}
.container {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    text-align: center;
    max-width: 400px;
}
input {
    padding: 10px;
    width: 80%;
    margin-bottom: 10px;
    border: 1px solid #ddd;
    border-radius: 5px;
}
.btn {
    background-color: #2ecc71;
    color: white;
    padding: 10px 20px;
    text-decoration: none;
    border-radius: 5px;
    border: none;
    cursor: pointer;
    display: inline-block;
}
.btn:hover { background-color: #27ae60; }
.error { color: #e74c3c; font-weight: bold; }