.overflow {
    height: 100%;
    width: 25vw;
    float: left;
    overflow: hidden;
}

.element {
    -webkit-transition: 1s ease-in-out;
    -moz-transition: 1s ease-in-out;
    -o-transition: 1s ease-in-out;
    transition: 1s ease-in-out;

    height: 100%;
    width: 25vw;
    float: left;
    background: url("../img/slider/a1.jpg") no-repeat center;
    background-size: cover;
    opacity: 0.5;
    overflow: hidden;
}
.element:hover {
    opacity: 1;
    transform: scale(1.05);
    overflow: hidden;
}

@media (max-aspect-ratio: 3/2) {
    .overflow {
        height: 100%;
        width: 50vw;
        float: left;
        overflow: hidden;
    }

    .element {
        height: 100%;
        width: 50vw;
        float: left;
        background: url("../img/slider/a1.jpg") no-repeat center;
        background-size: cover;
    }
}

.a1 {
    background-image: url("../img/slider/a1.jpg");
}

.a2 {
    background-image: url("../img/slider/a2.jpg");
}

.a3 {
    background-image: url("../img/slider/a3.jpg");
}

.a4 {
    background-image: url("../img/slider/a4.jpg");
}
.a5 {
    background-image: url("../img/slider/a5.jpg");
}

.a6 {
    background-image: url("../img/slider/a6.jpg");
}

.b1 {
    background-image: url("../img/slider/b1.jpg");
}

.b2 {
    background-image: url("../img/slider/b2.jpg");
}

.b3 {
    background-image: url("../img/slider/b3.jpg");
}

.b4 {
    background-image: url("../img/slider/b4.jpg");
}
.b5 {
    background-image: url("../img/slider/b5.jpg");
}

.b6 {
    background-image: url("../img/slider/b6.jpg");
}

.c1 {
    background-image: url("../img/slider/c1.jpg");
}

.c2 {
    background-image: url("../img/slider/c2.jpg");
}

.c3 {
    background-image: url("../img/slider/c3.jpg");
}

.c4 {
    background-image: url("../img/slider/c4.jpg");
}
.c5 {
    background-image: url("../img/slider/c5.jpg");
}

.c6 {
    background-image: url("../img/slider/c6.jpg");
}

.d1 {
    background-image: url("../img/slider/d1.jpg");
}

.d2 {
    background-image: url("../img/slider/d2.jpg");
}

.d3 {
    background-image: url("../img/slider/d3.jpg");
}

.d4 {
    background-image: url("../img/slider/d4.jpg");
}
.d5 {
    background-image: url("../img/slider/d5.jpg");
}

.d6 {
    background-image: url("../img/slider/d6.jpg");
}