Just my take on a concept for Twitter for OS X Yosemite. (There is no green button, because there is no full screen mode, it's simple as that.)
I recommend you to check out the attachment.
Inspired by Tweetbot 2 (Yosemite) by Ilja Miskov.
By the way this is my first attempt on Sketchapp and I really like this tool for designing so far!
I am on Twitter.