How to apply ‘new’ graphic to new topics

[sheng_hualuo (花落晓斩神)]

.badge-notification.new-topic::before {
    content: "New!";
    position: absolute;
    right: -1.1em;
    top: -0.85em;
    background: var(--quaternary);
    transform: rotate(12deg);
    font-size: var(--font-down-2);
    letter-spacing: .05em;
    padding: .2em .5em;
    border-radius: 4px;
    font-weight: normal;
    color: var(--secondary);
}