*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body{
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
    min-height: 100vh;
    background: #18191f;
}

ul{
    position: relative;
    display: flex;
    margin: 10px 0;
}

ul li{
    position: relative;
    list-style: none;
}

ul li a{
    display: block;
    width: 50px;
    height: 50px;
    background: #18191f;
    line-height: 55px;
    text-align: center;
    margin: 0 10px;
    border-radius: 15px;
    box-shadow: -2px -2px 3px rgba(255, 255, 255, 0.05),
                3px 3px 3px rgba(0, 0, 0, 0.2);
}

ul li a .fa{
    font-size: 22px;
    color: #555;
}

ul li a:hover .fa{
    color: #00f3ff;
    text-shadow: 0 0 15px #00f3ff;
}

ul:nth-child(2) li a:hover .fa{
    color: #f00;
    text-shadow: 0 0 15px #f00;
}

ul:nth-child(3) li a:hover .fa{
    color: #0f0;
    text-shadow: 0 0 15px #0f0;
}

ul:nth-child(4) li a:hover .fa{
    color: yellow;
    text-shadow: 0 0 15px yellow;
}