BirdNET-stream/www/assets/styles/menu.css

nav {
    --nav-width: 20em;
    --nav-bg: lightgrey;
    --burger-size: 5em;
    --burger-weight: 3px;
    position: fixed;
    top: 0;
    left: 0;
    width: 0;
    z-index: 10;
}

.toggler {
    z-index: 21;
    height: var(--burger-size);
    width: var(--burger-size);
    align-items: center;
    justify-content: center;
    padding: 0.6rem;
    position: fixed;
    cursor: pointer;
    opacity: 0;
}

.hamburger {
    position: fixed;
    top: 0;
    left: 0;
    height: var(--burger-size);
    width: var(--burger-size);
    padding: 0.6rem;
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 20;
    opacity: 1;
}

.hamburger>div {
    position: relative;
    top: 0;
    left: 0;
    background: black;
    height: var(--burger-weight);
    width: 75%;
    transition: all 0.4s ease;
    color: #000;

}

.hamburger>div::before,
.hamburger>div::after {
    content: '';
    position: absolute;
    top: 10px;
    background: black;
    width: 100%;
    height: var(--burger-weight);
    transition: all 0.4s ease;
}

.hamburger>div::after {
    top: -10px;
}

.toggler:checked+.hamburger>div {
    background-color: var(--nav-bg);
}

.toggler:checked+.hamburger>div::before {
    top: 0;
    transform: rotate(45deg);
    background: black;
}

.toggler:checked+.hamburger>div::after {
    top: 0;
    transform: rotate(135deg);
    background: black;
}

.menu {
    height: 100vh;
    width: 0;
    visibility: hidden;
}

.toggler:checked~.menu {
    width: fit-content;
    height: fit-content;
    background-color: var(--nav-bg) !important;
}

.menu>ul {
    display: flex;
    flex-direction: column;
    position: fixed;
    width: 0;
    height: calc(100vh - var(--burger-size));
    padding-left: 1em;
    padding-right: 1em;
    margin-top: var(--burger-size);
    visibility: hidden;
    background-color: var(--nav-bg);
    z-index: 10;
}

.menu>ul>li {
    list-style: none;
    padding: 0.5rem;
}

.menu>ul>li>a {
    color: black;
    text-decoration: none;
    font-size: var(--font-size);
}

.toggler~.fill {
    display: none;
}

.toggler:checked~.fill {
    background: var(--nav-bg);
    position: absolute;
    top: 0;
    left: 0;
    height: var(--burger-size);
    width: var(--nav-width);
    display: block;
    z-index: 10;
}

.toggler:checked~.menu>ul {
    width: 20em;
    transition: fit-content .5s ease;
    opacity: 1;
    transition: opacity .5s, visibility .5s, height .5s, width .5s;
    visibility: visible;
}

.toggler:checked~.menu>ul>li>a:hover {
    color: orange;
}


@media screen and (max-width: 700px) {
    nav {
        --burger-size: 4em;
    }
}