.active {
    font-weight: bold;
}
.container {
    display: flex;
    flex-flow: row wrap;
}
.container > * {
    border: 1px solid;
    padding: 0.5em;
    margin: 0.5em;
    flex: 1 1 75px;
}
.container > a.active {
    background: lightgray;
}