.topnav li a {
    position: relative;
    z-index: 0;
    cursor: pointer;
}

.topnav li a:before, .topnav li a:after {
    position: absolute;
    top: 50%;
    left: 50%;
    width: 35px;
    height: 35px;
    border: 4px solid #0277bd;
    transform: translateX(-50%) translateY(-50%) scale(0.8);
    border-radius: 50%;
    background: transparent;
    content: "";
    opacity: 0;
    transition: all 0.3s;
    z-index: -1;
}

.topnav li a:after {
    border-width: 2px;
    transition: all 0.4s;
}

.topnav li a:hover:before {
    opacity: 1;
    transform: translateX(-50%) translateY(-50%) scale(1);
}

.topnav li a:hover:after {
    opacity: 1;
    transform: translateX(-50%) translateY(-50%) scale(1.3);
}