style.css

@import url('https://fonts.googleapis.com/css2?family=Bad+Script&display=swap');

* {
    margin: 0;
    padding: 0;
    user-select: none;
    box-sizing: border-box;
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    background: #000;
    font-family: 'Bad Script', cursive;
    height: 100vh;
}

h1 {
    color: #111;
    font-size: 16em;
}

h1 span {
    display: table-cell;
    animation: animate 2s linear infinite;
}

h1 span:nth-child(1) {
    animation-delay: 0s;
}

h1 span:nth-child(2) {
    animation-delay: 0.25s;
}

h1 span:nth-child(3) {
    animation-delay: 0.5s;
}

h1 span:nth-child(4) {
    animation-delay: 0.75s;
}

h1 span:nth-child(5) {
    animation-delay: 1s;
}

h1 span:nth-child(6) {
    animation-delay: 1.25s;
}

h1 span:nth-child(7) {
    animation-delay: 1.5s;
}

h1 span:nth-child(8) {
    animation-delay: 1.75s;
}

@keyframes animate {
    0%, 100% {
        color: #fff;
        filter: blur(2px);
        text-shadow: 0 0 10px #00b3ff,
        0 0 20px #00b3ff,
        0 0 40px #00b3ff,
        0 0 80px #00b3ff,
        0 0 120px #00b3ff,
        0 0 200px #00b3ff,
        0 0 300px #00b3ff,
        0 0 400px #00b3ff;
    }

    5%, 95% {
        color: #111;
        filter: blur(0px);
        text-shadow: none;
    }
}

@media screen and (min-width: 300px) and (max-width: 800px) {
    h1 {
        font-size: 6em;
    }
}