<p>テキスト</p>
<p>テキスト</p>
<p>テキスト</p>
p {
  width:70px;
  background-color:red;
  transition-duration: 2s;
  transition-property:width;
}
p:hover {
  width:200px;
  background-color:blue;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.