responsive design with floating images

So, here's what I'm trying to do: I want the images to float, but when the screen shrinks, I want one to go under the other. Here's the jsfiddle so you can understand exactly. I want the first one float to the left, while the second one float to the right:

[jsfiddle][1]

  [1]: http://ift.tt/1DQlhSD