.image-container {
    position: relative;
    width: 200px;
    height: 200px;
    transform-style: preserve-3d;
    transform: perspective(1000px) rotateY(0deg);
    transition: transform .7s;
}

    .image-container span {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        transform: rotateY(calc(var(--i)*45deg)) translateZ(400px);
    }

        .image-container span img {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
        }

.btn-container {
    position: relative;
    width: 80%;
    justify-content: space-between;
}

.btn {
    position: absolute;
    bottom: -80px;
    background-color: slateblue;
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: 5px;
    cursor: pointer;
}

    .btn:hover {
        filter: brightness(1.5);
    }

#prev {
    left: 20%;
}

#next {
    right: 20%;
}