HTMLify

* {
    margin: 0;
    box-sizing: border-box;
    font-family: HelveticaNeue, Helvetica, sans-serif;
}

nav {
    color: white;
}

.hamburger {
    position: fixed;
    top: 0;
    right: 0;
    z-index: 10;
    display: flex;
    align-items: center;
    width: 25px;
    height: 15px;
    margin: 40px;
    color: #3c4b9f;
    cursor: pointer;
}

.hamburger::before {
    content: "";
    position: absolute;
    inset: -5px;
    background: #3c4b9f;
    opacity: 0;
    z-index: -1;
    transition: opacity 0.3s cubic-bezier(0.75, 0, 0.25, 1);
}

.hamburger span {
    display: block;
    width: 100%;
    height: 2px;
    transition: transform 1s cubic-bezier(0.75, 0, 0.25, 1);
    background: currentColor;
}

.hamburger span::before,
.hamburger span::after {
    content: "";
    position: absolute;
    left: 0;
    right: 0;
    display: block;
    height: 2px;
    background: currentColor;
    transition: transform 0.4s cubic-bezier(0.75, 0, 0.25, 1),
        top 0.4s 0.4s cubic-bezier(0.75, 0, 0.25, 1),
        background 0.2s cubic-bezier(0.75, 0, 0.25, 1);
}

.hamburger span::before {
    top: 0;
}

.hamburger span::after {
    top: calc(100% - 2px);
}

.input__control {
    opacity: 0;
    width: 0;
    height: 0;
    appearance: none;
    position: fixed;
}

.input__control:focus+label {
    color: white;
}

.input__control:focus+label::before {
    opacity: 1;
}

.input__control:checked+label {
    height: 10px;
    color: white;
}

.input__control:checked+label span {
    transform: rotate(45deg);
}

.input__control:checked+label span::before,
.input__control:checked+label span::after {
    top: calc(50% - 1px);
    transition: transform 0.4s 0.4s cubic-bezier(0.75, 0, 0.25, 1),
        top 0.4s cubic-bezier(0.75, 0, 0.25, 1),
        background 0.2s cubic-bezier(0.75, 0, 0.25, 1);
}

.input__control:checked+label span::after {
    transform: rotate(90deg);
}

.input__control:checked~ul {
    z-index: 9;
    transform: none;
    transition: 0.5s cubic-bezier(0.75, 0, 0.25, 1);
}

.nav__list {
    position: fixed;
    inset: 0;
    z-index: -1;
    background: #3c4b9f;
    font-size: 4rem;
    padding: 40px;
    transform: translate(100vw) rotate(45deg);
    transition: 0.2s cubic-bezier(0.75, 0, 0.25, 1);
}

.nav__item {
    list-style: none;
}

.nav__item+.nav__item {
    margin-top: 20px;
}

.nav__link {
    text-decoration: none;
    color: inherit;
}