center div inside div with absolute position using flexbox

Question

Other problem center using css, I wish center a div inside other div with absolute position, I want to get a similar result to this image:

preferably using flexbox, example code:

.abs_1 {
  position: absolute;
  background: red;
  height: 200px;
  width: 200px;
  top: 40px;
  left: 40px;
}

.abs_2 {
  position: absolute;
  background: blue;
  height: 200px;
  width: 200px;
  top: 60px;
  left: 250px;
}

.center{
    display: flex;
    justify-content: center;
    align-items: center;
}

.center div {
  background: black;
  color: white;
}

<div class="abs_1">
  <div class="center">
      <div>Hello.</div>
  </div>
</div>

<div class="abs_2">
  <div class="center">
      <div>World</div>
  </div>
</div>

I get the following:

could you do this using flex css?

Answer 1

Here is a solution using CSS Flexbox.

CSS

#container {
    display: flex;
    justify-content: center;
    align-items: center;
}

.abs_1 {
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 10px;
    background: red;
    height: 200px;
    width: 200px;
}

.abs_2 {
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 10px;
    background: blue;
    height: 200px;
    width: 200px;
}

.center > div {
    background: black;
    color: white;
}

HTML

<div id="container">

    <div class="abs_1">
        <div class="center">
            <div>Hello.</div>
        </div>
    </div>

    <div class="abs_2">
        <div class="center">
            <div>World</div>
        </div>
    </div>

</div><!-- end #container -->

DEMO: http://jsfiddle.net/3ekyetc0/