A modern card based login screen designed by Mikael Ainalem. The active element has a gradient underline and as soon as you click on another element the underline slithers over to the new one kinda like a snake.
If you are having trouble with the pen, try the archived copy on GitHub
Slithering Underline Highlighter Snippet
See the Pen Snake highlight by Mikael Ainalem (@ainalem) on CodePen.0