center with flex

.primary-nav {
    display:-webkit-flex;
    display:flex;
    list-style-type:none;
    padding:0;
    justify-content:flex-end;
}

.left {
    margin-right:auto;
}

.container {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100%;
}