.firework {
    position: absolute;
    width: 10px;
    height: 10px;
    background-color: #ff0;
    border-radius: 50%;
    animation: explode 1s ease-out;
}

@keyframes explode {
    0% {
        transform: scale(1);
        opacity: 1;
    }
    100% {
        transform: scale(3);
        opacity: 0;
    }
}