style.css

body {
    background-color: #000;
}

#effect {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

#effect span {
    font-family: verdana;
    font-size: 30px;
    display: inline-block;
    animation: animate 1s linear infinite;
    width: 50px;
    height: 50px;
    text-align: center;
    line-height: 50px;
    margin: 0 -2.5px;
}


/* #effect .sp {
    visibility: hidden;
} */

@keyframes animate {
    10% {
        color: rgba(0, 255, 0, 1);
        box-shadow: 0 2px 10px rgba(0, 255, 0, 1);
        border: 2px solid rgba(0, 255, 0, 1);
    }
    30.3% {
        color: rgb(255, 255, 255);
        box-shadow: 0 2px 10px rgb(255, 255, 255);
        border: 2px solid rgb(255, 255, 255);
    }
    90% {
        color: rgb(255, 51, 0);
        box-shadow: 0 2px 10px rgb(255, 51, 0);
        border: 2px solid rgb(255, 51, 0);
    }
}

#effect span:nth-child(1) {
    animation-delay: 0s;
}

#effect span:nth-child(2) {
    animation-delay: 0.1s;
}

#effect span:nth-child(3) {
    animation-delay: 0.2s;
}

#effect span:nth-child(4) {
    animation-delay: 0.3s;
}

#effect span:nth-child(5) {
    animation-delay: 0.4s;
}

#effect span:nth-child(6) {
    animation-delay: 0.5s;
}

#effect span:nth-child(7) {
    animation-delay: 0.6s;
}

#effect span:nth-child(8) {
    animation-delay: 0.7s;
}

#effect span:nth-child(9) {
    animation-delay: 0.8s;
}