This is such bad web design its amazing

Go to the Twitter.com on mobile in a private browsing window or basically be not logged in. The standard popup will come up asking you to logon.

In the top left is a small X you can click to close this popup and continue to twitter without loggin in. In the center top left is the new X logo which is just slightly larger. I immediately clicked on the larger X and of course nothing happened. I then realized it was the smaller but very similar X in the upper left hand corner I needed to click to close the popup.

How is the basic design this bad?