margin-top only when the flex item is wrapped

问题:

I have a flex container with two flex items. I want to set a margin-top on the second one, but only when it's wrapped and not at the first flex line.

If possible, I want to avoid using media queries.

I thought margin-bottom on the first element could be a solution. However, it adds space at the bottom when the elements are not wrapped, so same problem.

This is my code:

.container {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-around;
}
.item-big {
  background: blue;
  width: 300px;
}
.item-small {
  background: red;
  margin-top: 30px;
}

<div class="container">
  <div class="item-big">
    FIRST BIG ELEM
  </div>
  <div class="item-small">
    SECOND SMALL ELEM
  </div>
</div>

回答1:

You can add some margin-top to both flex items, and a negative margin-top of the same amount to the flex container.

This way, the negative margin of the flex container will neutralize the margin of the flex items at the first line, but not the margin of the items that wrapped to other lines.

.container {
  margin-top: -30px;
}
.item-big, .item-small {
  margin-top: 30px;
}

.container {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-around;
  margin-top: -30px;
}
.item-big, .item-small {
  margin-top: 30px;
  background: red;
}
.item-big {
  background: blue;
  width: 300px;
}

<div class="container">
   <div class="item-big">
      FIRST BIG ELEM
   </div>
   <div class="item-small">
      SECOND SMALL ELEM
   </div>
</div>

回答2:

.container {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-around;
}

.item-big {
    background: blue;
    margin-top: 30px;
    width: 300px;
}

.item-small {
    background: red;
    margin-top: 30px;
    width: 300px;
}

<div class="container">

   <div class="item-big">
      FIRST BIG ELEM
   </div>
   
   <div class="item-small">
      SECOND SMALL ELEM
   </div>
</div>