Center animation text - animation

Question

Hello there I am completely new in design and struggling since a few days to resolve this issue but may be I need some help with you guys. Here is the result of what I want to achieve:
https://tobiasahlin.com/moving-letters/#4
the titles must appears in the center of the row
and here is my result:
https://codepen.io/Amidamaro/pen/dyMZMYP
HTML:
<h1 class="ml4">
<span class="letters letters-1">Ready</span>
<span class="letters letters-2">Set</span>
<span class="letters letters-3">Go!</span>
</h1>
<script src="https://cdnjs.cloudflare.com/ajax/libs/animejs/2.0.2/anime.min.js"></script>
CSS:
.ml4 {
width: 100%;
height: 100px;
position: relative;
display: flex;
}
.ml4 .letters {
position: absolute;
margin: auto;
left: 0;
top: 0.3em;
right: 0;
opacity: 0;
justify-content: center;
}
JS:
var ml4 = {};
ml4.opacityIn = [0, 1];
ml4.scaleIn = [0.2, 1];
ml4.scaleOut = 3;
ml4.durationIn = 800;
ml4.durationOut = 600;
ml4.delay = 500;
anime
.timeline({ loop: true })
.add({
targets: ".ml4 .letters-1",
opacity: ml4.opacityIn,
scale: ml4.scaleIn,
duration: ml4.durationIn
})
.add({
targets: ".ml4 .letters-1",
opacity: 0,
scale: ml4.scaleOut,
duration: ml4.durationOut,
easing: "easeInExpo",
delay: ml4.delay
})
.add({
targets: ".ml4 .letters-2",
opacity: ml4.opacityIn,
scale: ml4.scaleIn,
duration: ml4.durationIn
})
.add({
targets: ".ml4 .letters-2",
opacity: 0,
scale: ml4.scaleOut,
duration: ml4.durationOut,
easing: "easeInExpo",
delay: ml4.delay
})
.add({
targets: ".ml4 .letters-3",
opacity: ml4.opacityIn,
scale: ml4.scaleIn,
duration: ml4.durationIn
})
.add({
targets: ".ml4 .letters-3",
opacity: 0,
scale: ml4.scaleOut,
duration: ml4.durationOut,
easing: "easeInExpo",
delay: ml4.delay
})
.add({
targets: ".ml4",
opacity: 0,
duration: 500,
delay: 500
});
I tried to display: flex; the parent and from there on to set the children to the center but nothing changes. Will appreciate any help, thanks !

Answer 1

Yeah! I've managed to solve this.
CSS:
.ml4 {
width: 100%;
height: 100px;
position: relative;
display: flex;
overflow: hidden;
}
.ml4 .letters {
position: absolute;
margin: auto;
left: 0;
top: 0.3em;
right: 0;
opacity: 0;
text-align: center;
}