body {
            font-family: Arial, sans-serif;
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            height: 100vh;
            margin: 0;
            background-color: #f8f9fa;
        }
        h1 {
            font-weight: bold;
            font-size: 2em;
            text-align: center;
        }
        p {
            color: #555;
            margin-top: 0;
        }
        .phone-input {
            display: flex;
            flex-direction: column;
            align-items: center;
        }
        input {
            padding: 10px;
            font-size: 1em;
            margin-bottom: 10px;
            border: 1px solid #ddd;
            border-radius: 5px;
            width: 300px;
            max-width: 90%;
        }
        button {
            padding: 10px 20px;
            font-size: 1em;
            color: #fff;
            background-color: #000;
            border: none;
            border-radius: 5px;
            cursor: pointer;
        }
.error-message {
    color: red;
    margin-top: 5px;
    margin-bottom: 10px;
    visibility: hidden;
}
.invalid-input {
    border-color: red;
}