* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
ul.menu {
    display: flex;
    list-style-type: none;
}
li.menu_list {
    height: 85px;
    width: 85px;
    position: relative;
}
li.menu_list .front,
a.side {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 86px;
    width: 100%;
    padding: 30px;
    position: absolute;
    top: 0;
    left: 0;
    text-decoration: none;
    text-transform: uppercase;
    transition: all .5s ease-out;
    cursor: pointer;

}
li.menu_list .front {
    background-color: #34465d;
    color: #FFFC00;
    transform-origin: 0 0;
}
a.side {
    background-color: #FFFC00;
    color: #34465d;
    transform-origin: 0 0 85px;
    transform: rotateX(90deg);
}
li.menu_list:hover a.side {
    transform: rotateX(0deg);
}
li.menu_list:hover .front {
    transform: rotateX(90deg);
}