How to make underline css popup?

Question

css

html.crunchpress.com/materialmag
in the footer, in the hover form, appeared. underlining. How to do so? (I can basically do everything myself, but it doesn’t work out so that it seems to blur from the center)

Answer 1

использовать анимацию css при событие active или hover по желанию.
www.w3schools.com/css/css3_animations.asp

Answer 2

Как вариант https://jsfiddle.net/joomla/us8kLmdc/