.btn-spinner {
    display: none;
    width: 18px;
    height: 18px;
    margin-left: 25px;
    border: 2px solid #ccc;
    border-top-color: #333;
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
    vertical-align: middle;
    position: absolute;
    top: calc(50% - 10px);
    padding-top: 10px !important;
}

@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}