Push border-bottom from left and right with some pixels - html

Question

I would like to know, if it is possible to give to a border-bottom something like a padding-left and padding-right. I have two divs, which have some borders. I would like to make the border-bottom of the top div to have some padding on left and right. I have no idea if this is possible. I know the structure is strange (I could easy use the border around the whole box wrapper and than work on the span with a border-bottom to achieve this). The problem is, I'm using a plugin which has a structure like this and I have to customize it like this, because there is exactly this strucure and styling. Hope it's clear enough. Here a picture how it should look and an example snippet:
.box {
display: flex;
flex-direction: column;
width: 200px;
}
.box__top {
border: 1px solid black;
border-bottom: 1px solid red;
height: 20px;
padding: 10px;
text-align: center;
}
.box__bottom {
border: 1px solid black;
border-top: none;
height: 150px;
padding: 10px;
text-align: center;
}
<div class="box">
<div class="box__top">
<span>I'm the top section</span>
</div>
<div class="box__bottom">
<span>I'm the top section</span>
</div>
</div>

Answer 1

Use a pseudo-element instead:
.box {
display: flex;
flex-direction: column;
width: 200px;
}
.box__top {
border: 1px solid black;
border-bottom: none;
position: relative;
height: 20px;
padding: 10px;
text-align: center;
}
.box__top::after {
content: " ";
position: absolute;
left: 50%;
transform: translateX(-50%);
bottom: 0;
width: 90%;
height: 1px;
background-color: red;
}
.box__bottom {
border: 1px solid black;
border-top: none;
height: 150px;
padding: 10px;
text-align: center;
}
<div class="box">
<div class="box__top">
<span>I'm the top section</span>
</div>
<div class="box__bottom">
<span>I'm the top section</span>
</div>
</div>