.slider {
    display: flex;
    justify-content: center;
    align-items: center;

}

.slider ul {
    display: block;
    list-style: none;
    position: relative; 
    height: 600px;
    width: 960px;
    margin-bottom: 20px;
}

.slider li {
    opacity: 0;
    position: absolute;
    left: 0;
    top: 0;
    transition: opacity 0.5s;

}


.slider .btn {
    margin: auto;
    background-color: rgb(116, 2, 100);
}

.slider .visible {
    opacity: 1;
}