*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
body {
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}
.box {
    position: relative;
    width: 100px;
    height: 100px;
    border-radius: 50%;
    background-color: black;
    
    animation: pulse 1s linear infinite;
}

@keyframes pulse {
    from {
        box-shadow: 0 0 0px 0px rgba(255, 0, 0, 1);
    }
    to {
        box-shadow: 0 0 20px 30px rgba(255, 0, 0, 0);
    }
}