.main-header
{
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid lightgray;
}

#menu
{
    background: none;
    border: none;
    cursor: pointer;

    font-size: 2em;
    padding: 15px 25px 15px 15px;

    display: none;
}

#menu:focus
{
    outline: 0;
}

.main-header h1
{
    font-size: 1.5em;
    margin: 0 0 0 20px;
}

.main-header h1 a
{
    color: black;
    text-decoration: none;
}

.main-header nav
{
    display: inline-flex;
    margin-right: 20px;
}

.main-header nav a
{
    font-family: Montserrat, sans-serif;
    font-weight: bold;
    text-decoration: none;

    margin-right: 20px;
    padding: 20px;
    border-bottom: 3px solid transparent;
}

.main-header nav a:hover
{
    border-bottom: 3px solid lightgray;
}

.main-header nav a.active
{
    cursor: default;
    pointer-events: none;

    color: black;
    font-weight: bold;
    border-bottom: 3px solid black;
}

@media (max-width: 767px)
{
    .main-header
    {
        flex-wrap: wrap;
    }

    #menu
    {
        display: block;
    }

    .main-header nav
    {
        flex-direction: column;

        width: 100%;
        max-height: 300px;
        overflow: hidden;
        transition: max-height 0.3s ease-out;
    }

    .main-header nav.hidden
    {
        max-height: 0;
    }

    .main-header nav a
    {
        padding-left: 30px;
        border-bottom: none;
        border-left: 3px solid transparent;
    }

    .main-header nav a:hover
    {
        border-bottom: none;
        border-left: 3px solid lightgray;
    }

    .main-header nav a.active
    {
        border-bottom: none;
        border-left: 3px solid black;
    }
}