<h2>Vertical Centering with Flexbox</h2>
<p>Both the container and the child element are resizable using a bottom-right handle. Try resizing either of them. The child box will remain vertically and horizontally centered inside the parent.</p>

<main class="container">
  <div class="item"><p>Try resizing this element or the container.</p></div>
</main>

body {
  font-family: Arial, sans-serif;
  font-size: 1.3em;
  padding: 0 2em 3em;
  line-height: 1.4;
}

h2 {
  margin-top: 14px;
  text-align: center;
}

.container {
  display: flex;
  align-items: center;
  justify-content: center;
  background: lightblue;
  min-height: 90px;
  min-width: 440px;
  height: 400px;
  padding: 1em;
  border: solid 2px;
  resize: both;
  overflow: auto;  
}

.item {
  background: pink;
  max-width: 60%;
  min-width: 400px;
  min-height: 2em;
  text-align: center;
  resize: both;
  overflow: hidden;
  border: solid 2px;
  padding: 1em;
  display: flex;
  justify-content: center;
  align-items: center;  
}

.item p {
  margin: 0;
  text-align: center;
}

@media (max-width: 560px) {
  .container, .item {
    min-width: auto;
  }
}