body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #f0f4f8;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
}

.container {
    background: white;
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    max-width: 450px;
    width: 100%;
}

h1 {
    text-align: center;
    color: #2c3e50;
    font-size: 24px;
    margin-bottom: 20px;
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
}

.form-group {
    margin-bottom: 20px;
}

label {
    display: block;
    margin-bottom: 8px;
    color: #34495e;
    font-weight: 600;
    font-size: 14px;
}

input {
    width: 100%;
    padding: 12px;
    border: 1px solid #bdc3c7;
    border-radius: 6px;
    box-sizing: border-box;
    transition: all 0.3s ease;
    font-size: 16px;
}

input:focus {
    outline: none;
    border-color: #3498db;
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.2);
}

input.invalid {
    border-color: #e74c3c;
    box-shadow: 0 0 0 3px rgba(231, 76, 60, 0.2);
}

input.valid {
    border-color: #2ecc71;
    box-shadow: 0 0 0 3px rgba(46, 204, 113, 0.2);
}

.error {
    color: #e74c3c;
    font-size: 0.85em;
    display: block;
    margin-top: 6px;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.error.visible {
    opacity: 1;
}

button {
    width: 100%;
    padding: 12px;
    background: linear-gradient(135deg, #27ae60, #2ecc71);
    color: white;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 16px;
    font-weight: 600;
    transition: all 0.3s ease;
    box-shadow: 0 2px 10px rgba(46, 204, 113, 0.3);
}

button:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(46, 204, 113, 0.4);
}

.success {
    color: #27ae60;
    text-align: center;
    margin-top: 15px;
    font-size: 16px;
    opacity: 0;
    transition: opacity 0.5s ease;
}

.success.visible {
    opacity: 1; /* Applied in JS on success */
}

/* Responsive adjustments */
@media (max-width: 480px) {
    .container {
        padding: 20px;
    }
    h1 {
        font-size: 20px;
    }
    input, button {
        font-size: 14px;
    }
}