#scrollTopBtn {
    display: none;
    position: fixed;
    bottom: 15px;
    right: 15px;
    z-index: 100;
    font-size: 18px;
    border: none;
    outline: none;
    background-color: #333;
    color: white;
    cursor: pointer;
    border-radius: 50%;
    transition: opacity 0.3s ease;
    height: 50px;
    width: 50px;
}