.button_container {
    position: fixed;
    top: 5%;
    right: 2%;
    height: 27px;
    width: 35px;
    cursor: pointer;
    z-index: 100;
    transition: opacity .25s ease;
}

.button_container:hover {
    opacity: .7;
}

.button_container.active .top {
    -webkit-transform: translateY(10px) translateX(0) rotate(45deg);
    transform: translateY(10px) translateX(0) rotate(45deg);
    background: #FFF;
}

.button_container.active .middle {
    opacity: 0;
    background: #FFF;
}

.button_container.active .bottom {
    -webkit-transform: translateY(-10px) translateX(0) rotate(-45deg);
    transform: translateY(-10px) translateX(0) rotate(-45deg);
    background: #FFF;
}

.button_container span {
    background: rgb(173, 165, 165);
    border: none;
    height: 5px;
    width: 100%;
    position: absolute;
    top: 0px;
    left: 0;
    transition: all .35s ease;
    cursor: pointer;
}

.button_container span:nth-of-type(2) {
    top: 10px;
}

.button_container span:nth-of-type(3) {
    top: 20px;
}

.nav-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    opacity: 1;
    visibility: hidden;
    transition: opacity .35s, visibility .35s, width .35s;
    z-index: 50;
}

.nav-overlay:before {
    content: '';
    background: rgb(255, 255, 255);
    left: -55%;
    top: 0;
    width: 50%;
    height: 100%;
    position: absolute;
    transition: left .35s ease;
}

.nav-overlay:after {
    content: '';
    background: rgb(255, 255, 255);
    right: -55%;
    top: 0;
    width: 50%;
    height: 100%;
    position: absolute;
    transition: all .35s ease;
}

.nav-overlay.open {
    opacity: .9;
    visibility: visible;
    height: 100%;
}

.nav-overlay.open:before {
    left: 0;
}

.nav-overlay.open:after {
    right: 0;
}

.nav-overlay.open li {
    -webkit-animation: fadeInRight .5s ease forwards;
    animation: fadeInRight .5s ease forwards;
    -webkit-animation-delay: .35s;
    animation-delay: .35s;
}

.nav-overlay.open li:nth-of-type(2) {
    -webkit-animation-delay: .45s;
    animation-delay: .45s;
}

.nav-overlay.open li:nth-of-type(3) {
    -webkit-animation-delay: .55s;
    animation-delay: .55s;
}

.nav-overlay.open li:nth-of-type(4) {
    -webkit-animation-delay: .65s;
    animation-delay: .65s;
}

.nav-overlay.open li:nth-of-type(5) {
    -webkit-animation-delay: .75s;
    animation-delay: .75s;
}

.nav-overlay nav {
    position: relative;
    height: 70%;
    top: 60%;
    -webkit-transform: translateY(-50%);
    transform: translateY(-50%);
    font-size: 50px;
    text-align: center;
    z-index: 100;
}

.nav-overlay ul {
    list-style: none;
    padding: 0;
    margin: 0 auto;
    display: inline-block;
    position: relative;
    height: 100%;
}

.nav-overlay ul li {
    display: block;
    height: 25%;
    height: calc(80% / 4);
    min-height: 50px;
    position: relative;
    opacity: 0;
}

.nav-overlay ul li a {
    display: block;
    position: relative;
    color: rgb(0, 0, 0);
    text-decoration: none;
    overflow: hidden;
    font-size: 1.5rem;
}

.nav-overlay ul li a:hover:after,
.nav-overlay ul li a:focus:after,
.nav-overlay ul li a:active:after {
    width: 100%;
}

.nav-overlay ul li a:after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    width: 0%;
    -webkit-transform: translateX(-50%);
    transform: translateX(-50%);
    height: 2px;
    background: rgb(5, 5, 5);
    transition: .35s;
}

@-webkit-keyframes fadeInRight {
    0% {
        opacity: 0;
        left: 20%;
    }
    100% {
        opacity: 1;
        left: 0;
    }
}

@keyframes fadeInRight {
    0% {
        opacity: 0;
        left: 20%;
    }
    100% {
        opacity: 1;
        left: 0;
    }
}