CSS Skill Bar Animation - html

Question

I am trying to create a skill bar where the background color of the progress slides in but the label for the Skill bar stays in the same place.
.skill-container * {
box-sizing: border-box;
}
.skill-container {
width: 100%;
border-radius: 5px;
background-color: lightgray;
margin: 20px 0;
overflow: hidden;
}
.skill-container .skill {
display: inline-block;
text-align: left;
color: white;
padding: 10px 0 10px 4px;
border-radius: inherit;
background-color: #312E81;
white-space: nowrap;
position: relative;
animation: animateLeft 1s ease-out;
}
#keyframes animateLeft {
from {
left: -100%
}
to {
left: 0
}
}
.skill-container .skill.skill-level-70 {
width: 70%
}
<div class="skill-container">
<span class="skill skill-level-70">CSS</span>
</div>
So far the animation works well, but the only thing I need to figure out is how to keep the text (CSS) on the left and animate the sliding of the background color to show the progress

Answer 1

Use a pseudo element for the background:
.skill-container .skill {
color: white;
background-color: lightgray;
margin: 5px 0;
padding: 10px 0 10px 4px;
overflow: hidden;
border-radius: 5px;
white-space: nowrap;
position: relative;
z-index:0;
}
.skill-container .skill::before {
content: "";
position: absolute;
background-color: #312E81;
border-radius: inherit;
z-index: -1;
top: 0;
bottom: 0;
left: 0;
animation: animateLeft 1s ease-out;
}
#keyframes animateLeft {
from {
transform: translateX(-100%);
}
}
.skill-container .skill.skill-level-70::before {
width: 70%
}
.skill-container .skill.skill-level-40::before {
width: 40%
}
.skill-container .skill.skill-level-100::before {
width: 100%
}
<div class="skill-container">
<div class="skill skill-level-100">CSS</div>
<div class="skill skill-level-70">HTML</div>
<div class="skill skill-level-40">PHP</div>
</div>
You can optimize with CSS variables:
.skill-container .skill {
color: white;
background-color: lightgray;
margin: 5px 0;
padding: 10px 0 10px 4px;
overflow: hidden;
border-radius: 5px;
white-space: nowrap;
position: relative;
z-index:0;
}
.skill-container .skill::before {
content: "";
position: absolute;
background-color: #312E81;
border-radius: inherit;
z-index: -1;
top: 0;
bottom: 0;
left: 0;
width:var(--l,0%);
animation: animateLeft 1s ease-out;
}
#keyframes animateLeft {
from {
transform: translateX(-100%);
}
}
<div class="skill-container">
<div class="skill" style="--l:100%">CSS</div>
<div class="skill" style="--l:70%">HTML</div>
<div class="skill" style="--l:40%">PHP</div>
</div>