A simple notification concept UI with a CTA pulsating indicator showing the number of new unread notification. When you click on it you get a tooltip like drop-down with the new and old messages, the old ones are slightly greyed out so it is visually different from the new ones.
If you are having trouble with the pen, try the archived copy on GitHub
Notification UI Snippet
See the Pen Notifications Concept by Guy Waldman (@guywald) on CodePen.0