header {
    width: 100%;
    position: fixed;
    top: 0;
    z-index: 9999;
    background-color: #000000;
}

header .social-toolbar ul {
    padding-top: 5px;
}

header .social-toolbar li {
    display: inline-block;
    background: white;
    width: 37px;
    height: 37px;
    border-radius: 50%;
    text-align: center;
    transition: opacity .2s ease-in-out;
    margin-right: 8px;
}

header .social-toolbar li:last-of-type {
    margin-right: 0;
}

header .social-toolbar img {
    width: 27px;
    height: 37px;
}

header .social-toolbar li:hover {
    opacity: 0.6;
}

@media only screen and (max-width: 600px) {
    header {
        position: relative;
    }
    header .social-toolbar img {
        width: 20px;
        height: 30px;
    }
    header .social-toolbar li {
        display: inline-block;
        background: white;
        width: 30px;
        height: 30px;
        border-radius: 50%;
        text-align: center;
        transition: opacity .2s ease-in-out;
        margin-right: 8px;
    }
}