.icon-zalo {
    display: inline-block;
    width: 1em;
    height: 1em;
    background-image: url('../images/zalo-icon.svg');
    background-size: contain;
    background-repeat: no-repeat;
    background-position: center;
    vertical-align: middle;
}

/* Hover effect */
.header-socials a:hover .icon-zalo {
    opacity: 0.8;
}