Implementation of CSS border length control function

<div class="content-block">
<div class="box-container">
<div class="border-top">border top</div>
</div>
<div class="box-container">
<div class="border-left">border left</div>
</div>
<div class="box-container">
<div class="border-right">border right</div>
</div>
<div class="box-container">
<div class="border-bottom">border bottom</div>
</div>
</div>

.box-container {
    position: relative;
    width: 90%;
    color: #777;
}
.border-top {
    background: #b4bcbf;
    padding: 15px;
}
    .border-top:before {
        content: '';
        position: absolute;
        left: 42%;
        top: 0;
        bottom: auto;
        right: auto;
        height: 7px;
        width: 50%;
        background-color: #8796a9;
    }
.border-left {
    background: #dfdad6;
    padding: 15px;
}
    .border-left:before {
        content: '';
        position: absolute;
        left: 0;
        top: 6%;
        bottom: auto;
        right: auto;
        height: 52%;
        width: 5px;
        background-color: #a89d9e;
    }
.border-right {
    background: #eee9c4;
    padding: 15px;
}
    .border-right:after {
        content: '';
        position: absolute;
        left: auto;
        top:auto;
        bottom: 5px;
        right: 0;
        height: 52%;
        width: 5px;
        background-color: #f39c81;
    }
.border-bottom {
    background: #bcdc9d;
    padding: 15px;
}
    .border-bottom:after {
        content: '';
        position: absolute;
        left: 18px;
        top:auto;
        bottom: 0;
        right: auto;
        height: 6px;
        width: 105px;
        background-color: #32b66b;
    }