I'm placing an unknown number of div elements inside of a flex container.
.container {
  border: 1px solid red;
  display: flex;
  flex-flow: row;
  flex-wrap: wrap;
  gap: 10px;
  width: 170px;
}
.element {
  flex: 0 0 auto;
  height: 50px;
  width: 50px;
  border: 1px solid blue;
}
<div class="container">
  <div class="element"></div>
  <div class="element"></div>
  <div class="element"></div>
  <div class="element"></div>
  <div class="element"></div>
</div>
Originally, the width of the container is 80% percents of the window, so its width varies.
I'd like to style each one of the wrapped rows like a shelf, so that there is a bottom-border (and other elements) below all elements in a line. In the example above - there should be 3 shelves, and if the container get's wider - there will be a fewer shelves.
Can I achieve that using CSS only?