When the browser width is more than 1000px the div.flex-container changes so that the to p-tags could be beside each others. They are however still above each other.
Wha
Using the column direction for Flexbox requires an explicit height in order for wrapping to work (see: http://codepen.io/cimmanon/pen/oyilE).
If you want to have newspaper style columns without using explicit heights, the multi-column module is what you're looking for.
http://codepen.io/cimmanon/pen/CcGlE
.flex-container {
-webkit-columns: 20em;
-moz-columns: 20em;
columns: 20em;
}