body {
    margin: 0;
    background-color: #acf;
}

.current {
    background-color: white;
}

header a, .contact a {
    text-decoration: none;
}

header a, footer a {
    color: inherit;
}

header.banner a {
    display: flex;
    align-items: center;
}
header.banner img {
    filter: brightness(0%);
    transition: filter 1s;
}
header.banner:hover img {
    filter: brightness(100%) sepia(100%);
}
header.banner h1 {
    margin: 0;
    transition: color 1s;
}
header.banner:hover h1 {
    color: #d82;
}

nav > ol, nav li.dropdown > ul {
    list-style-type: none;
    padding-left: 0;
}
nav > ol > li > a {
    display: block;
    padding: 0.5em 0.1em;
}
nav li.dropdown > ul > li a img {
    width: 1em;
    height: 1em;
}

.lang {
    background-color: black;
    border-radius: 50% 50% 50% 0;
    color: white;
    padding: 0.5em;
}

footer.social > .content {
    display: flex;
    flex-direction: column;
    align-items: center;
}

footer.legal {
    grid-column: 1 / -1;
    width: 100%;
    text-align: center;
    margin: auto;
    font-size: 75%;
}

@media (min-width: 40em) {
    .togglable > input.toggle,
    .togglable > img.button,
    .togglable > label {
        display: none;
    }

    body {
        min-height: 100vh;
        display: grid;
        grid-template-columns: 2fr 1fr 3fr 1fr 1fr;
        grid-template-rows: auto 1fr auto;
    }

    header.banner {
        grid-column: 1;
    }
    header.banner img {
        width: 10rem;
    }
    header.banner h1 {
        font-size: 1.5rem;
    }

    header.menu {
        grid-column: 3 / -1;
    }
    header.menu > .content {
        display: grid;
        grid-template-columns: 3fr 1fr 1fr;
    }

    header.menu nav {
        grid-column: 1;
        margin-top: 2rem;
    }
    header.menu .lang {
        grid-column: 3;
    }

    nav > ol {
        display: flex;
        align-items: center;
        align-content: stretch;
        flex-wrap: wrap;
        text-align: center;
    }

    nav > ol > li {
        flex: 1;
    }

    nav li.dropdown {
        position: relative;
    }
    nav li.dropdown ul {
        position: absolute;
        width: 100%;
        text-align: left;
        background: lightgrey;
        z-index: 1;

        overflow: hidden;
        max-height: 0;
        transition: max-height 0.5s;
    }
    nav li.dropdown:hover ul {
        /* ⚠ Magic constant: must be big enough to show the whole dropdown,
       but not too big otherwise the transition will be "delayed". */
        max-height: 5em;
    }
    nav li.dropdown > ul > li {
        list-style-type: none;
    }
    nav li.dropdown > ul > li:hover {
        background: white;
    }
    nav li.dropdown > ul > li a {
        display: block;       /* Make link span whole containing block. */
        padding-inline-start: 10%;
    }

    .lang {
        grid-column: 5;
        margin: auto;
        margin-top: 3rem;
    }

    main {
        grid-row: 2;
        grid-column: 1 / -2;
        padding-left: 4%;
    }

    footer.social {
        grid-row: 2;
        grid-column: 5;
        position: sticky;
        top: 0;
    }

    .social img {
        width: 2em;
        margin-top: 0.5em;
        margin-bottom: 0.5em;
    }

    .contact {
        /* Ideally should be just: */
        /* writing-mode: sideways-lr; */
        /* but of course We Can't Have Nice Things. */
        writing-mode: vertical-rl;
        transform: rotate(180deg);

        margin: 0;
        padding: 1em 0.5em;
    }
}

@media (max-width: 40em) {
    body {
        display: grid;
        grid-template-columns: 2fr 1fr;
        grid-template-rows: auto auto 1fr auto;
        min-height: 100vh;
    }

    header.banner {
        grid-row: 1 / 3;
        grid-column: 1;
    }
    header.menu {
        grid-row: 1;
        grid-column: 2;
    }
    footer.social {
        grid-row: 2;
        grid-column: 2;
    }
    footer.legal {
        grid-row: 4;
    }
    main {
        grid-row: 3;
        grid-column: 1 / -1;
        padding: 0.8em;
    }

    header.menu {
        --open-button-size: 2.4rem;
    }
    header.menu > label {
        font-size: 1.2rem;
    }
    footer.social {
        --open-button-size: 1.8rem;
    }
    footer.social > label {
        font-size: 0.8rem;
    }

    /* Ideally, we'd use display: grid to have labels aligned.
     * Unfortunately, afaict on mobile Safari brainfarts and fails to
     * move the input to its fixed top-right position when it is
     * checked; instead it moves it… somewhere…
     *
     * Use display: flex, absolute positions, and margins instead.
     */
    .togglable {
        display: flex;
        position: relative;
        align-items: center;
        --open-button-max-size: 2.4rem;
        --close-button-size: 2rem;
        --togglable-origin: left;
        --togglable-transform: translate(-100vw);
    }
    .togglable > input.toggle {
        position: absolute;
        margin: 0;
        margin-left: calc(var(--open-button-max-size) - var(--open-button-size));
        width: var(--open-button-size);
        height: var(--open-button-size);
        opacity: 0;
        cursor: pointer;
    }
    .togglable > img.button.open {
        margin-left: calc(var(--open-button-max-size) - var(--open-button-size));
        padding: calc(0.1 * var(--open-button-size));
        width: calc(0.8 * var(--open-button-size));
        height: calc(0.8 * var(--open-button-size));
        object-fit: contain;
        object-position: center;
    }
    .togglable > img.button.close {
        display: block;
        position: fixed;
        top: calc(var(--close-button-size) / 2);
        right: calc(var(--close-button-size) / 2);
        width: var(--close-button-size);
        height: var(--close-button-size);
        margin: 0;
        transform-origin: var(--togglable-origin);
        transform: var(--togglable-transform);
        transition: transform 0.5s;
        z-index: 4;
    }
    .togglable > label {
        position: absolute;
        left: calc(1.2 * var(--open-button-max-size));
        cursor: pointer;
    }
    .togglable > .content {
        display: block;
        position: fixed;
        overflow: auto;
        width: 100vw;
        height: 100vh;
        top: 0;
        left: 0;
        margin: 0;
        background: #dddd;
        transform-origin: var(--togglable-origin);
        transform: var(--togglable-transform);
        transition: transform 0.5s;
        z-index: 3;
    }
    .togglable > input.toggle:checked {
        display: block;
        position: fixed;
        top: calc(var(--close-button-size) / 2);
        right: calc(var(--close-button-size) / 2);
        width: var(--close-button-size);
        height: var(--close-button-size);
        z-index: 5;
    }
    .togglable > input.toggle:checked ~ img.button.close {
        transform: none;
    }
    .togglable > input.toggle:checked ~ .content {
        transform: none;
    }

    header.banner img {
        width: 4rem;
        height: 4rem;
    }
    header.banner h1 {
        font-size: 1.6rem;
    }

    header.menu .content {
        display: grid;
        --cell-size: calc(var(--close-button-size) * 2);
        grid-template-columns: auto var(--cell-size);
        grid-template-rows: var(--cell-size) var(--cell-size) auto;
    }
    header.menu .content nav {
        grid-row: 1 / -1;
        grid-column: 1;
        padding: 2rem;
    }
    header.menu .content .lang {
        grid-row: 2;
        grid-column: 2;
        margin: auto;
    }

    .social > .content img {
        width: 3em;
        margin-top: 0.5em;
        margin-bottom: 0.5em;
    }
    .contact {
        padding: 1em;
    }
}