Focus is one of those additions which turns Emacs usage into real joy and makes programmer’s life happier.
Having to look at tons of code 8 hrs per day might become a bit painful. Readable font is often first choice to improve this situation but it doesn’t help much when one needs to focus on concrete block of code. This is where Focus comes to the rescue - it dims text outside the function pointed by cursor and visually brings that code block at user’s attention.
Try it out and keep calm while watching your code.