Notable is a very simple and versatile text editor to use. I use it to keep track of my ideas and notes in markdown.
In the first video some ideas a 'zen mode' the hide the main user and focus only on the content.
In the second video I've prototyped the way how the sidebar can be hidden, the zen mode and shared my vision of what the mobile version of Notable could look like.
Update: Although I like and enjoy Notable, I am no longer using it, in favor of Obsidian.