How to make a drop down menu from a button?

Question

css

How to make a drop down menu from a button? Click on the three dots and the menu will pop up.
PS I'm learning ;( I don't understand how to style, and how is it falling out?
https://getmdl.io/templates/blog/index.html

<ul class = "menu">
              <li><a href="about.html">About</a></li>
              <li><a href="message.html">Message</a></li>
              <li><a href="#office">Office</a></li>
              <li><a href="#contact">Contact</a></li>
</ul>

Answer 1

In your example, find div.mdl-menu__container . It is precisely positioned in the container. At the moment of clicking on the dots, the is-visible class is added to it , which makes it visible.
Open the inspector in Chrome, click on the dots and see what attributes change on the elements.