#fullscreen-btn {
    position: absolute;
    top: 10px;
    left: 10px;
    z-index: 1000;
    width: 200px;
    height: 150px;
    font-size: 30px;
    background-color: #333;
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-family: inherit;
    transition: background-color 0.3s ease;
}

#fullscreen-btn:hover {
    background-color: #555;
}