.header-nav-btn {
    background: none;
    border: none;
    outline: none;
    font-family: inherit;
    font-size: 1.15rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: #111;
    cursor: pointer;
    padding: 0;
    position: relative;
    transition: color 0.2s;
}

.header-nav-btn.active {
    color: #111;
}

.header-nav-btn.active::after {
    content: "";
    display: block;
    margin: 0 auto;
    width: 2.2em;
    border-bottom: 4px solid #111;
    margin-top: 0.3em;
}
 
.header-nav-btn:hover,
.header-nav-btn:focus {
    color: #222;
}