Ommwriter is a real love it or hate it piece of software. I am pretty solidly in the love camp. It comes with loads of restrictions functionality-wise, but is truly immersive and is quite thoughtful in its soundscape. The music stops and starts over if you switch windows, so it’ll keep me from alt-tabbing in ways other apps won’t.
I don’t use it a lot bc of said lack of function, but for freewriting, pomodoros, or hammering out a focused bit on this or that it’s pretty great imo. For some reason Ommbits was buggy for me or didn’t fit my workflow. I can’t remember, but maybe I’ll give it another go.