HTMLify

html {
    box-sizing: border-box;
}

*,
*:after,
*:before {
    box-sizing: inherit;
}

html {
    width: 100%;
    height: 100%;
}

body {
    background: #161616;
    width: 100%;
    height: 100%;
    font-family: Arial, Helvetica, sans-serif;
    color: #fff;
    padding: 60px;
}

.open {
    position: fixed;
    top: 40px;
    right: 40px;
    width: 50px;
    height: 50px;
    display: block;
    cursor: pointer;
    transition: opacity 0.2s linear;
}

.open:hover {
    opacity: 1;
}

.open span {
    display: block;
    float: left;
    clear: both;
    height: 4px;
    width: 40px;
    border-radius: 40px;
    background-color: #fff;
    position: absolute;
    right: 40px;
    top: 3px;
    overflow: hidden;
    transition: all 0.4s ease;
}

.open span:nth-child(1) {
    margin-top: 10px;
    z-index: 9;
}

.open span:nth-child(2) {
    margin-top: 25px;
}

.open span:nth-child(3) {
    margin-top: 40px;
}

.menu__list {
    transition: all 0.8s cubic-bezier(0.68, -0.55, 0.265, 1.55);
    height: 0;
    width: 0;
    right: 0;
    top: 0;
    position: absolute;
    background-color: rgba(42, 144, 98, 0.663);
    border-radius: 50%;
    z-index: 18;
    overflow: hidden;
}

.menu__list li {
    display: block;
    float: right;
    transition: all 0.5s cubic-bezier(0.68, -0.55, 0.265, 1.55);
}

.menu__list li:first-child {
    margin-top: 180px;
}

.menu__list li:nth-child(1) {
    transition-delay: 0.05s;
}

.menu__list li:nth-child(2) {
    transition-delay: 0.1s;
}

.menu__list li:nth-child(3) {
    transition-delay: 0.15s;
}

.menu__list li:nth-child(4) {
    transition-delay: 0.2s;
}

.menu__list li:nth-child(5) {
    transition-delay: 0.25s;
}

.menu__list li a {
    color: #fff;
    text-decoration: none;
    line-height: 40px;
}

.opened .menu__list {
    opacity: 1;
    height: 400px;
    width: 400px;
}

.opened span:nth-child(2) {
    overflow: visible;
}

.opened span:nth-child(1),
.opened span:nth-child(3) {
    z-index: 100;
    transform: rotate(45deg);
}

.opened span:nth-child(1) {
    transform: rotate(45deg) translateY(12px) translateX(12px);
}

.opened span:nth-child(2) {
    height: 400px;
    width: 400px;
    right: -160px;
    top: -160px;
    border-radius: 50%;
    background-color: rgba(42, 144, 98, 0.663);
}

.opened span:nth-child(3) {
    transform: rotate(-45deg) translateY(-10px) translateX(10px);
}

.opened li {
    margin-right: 200px;
}