Wow! This is a really straight forward solution to run something like breathe on linux, really cool! Do you mind if I put this as an alternative on the readme while I code up a cross-platform solution?
Just a side note, based on my experience and reading “the healing power of breath” , it might be that if you are below average size or above average size, the optimal rhythm might be different for you.
-> imv: https://github.com/eXeC64/imv (or any other really lightweight gif viewer)
-> breathe.gif: https://quietkit.com/img/box-breathing-4x-v03.gif
-> Set it to a custom shortcut and press q to close window.