Very high quality app, thank you! It's simple, looks nice, and does everything it needs to. I love that it automatically allows playing in the background and appears on the lock screen, etc.

The only thing I noticed was there's another app also called Ambi that generates background sound which I mistakenly downloaded first. It popped up a message to buy premium, then I knew I had the wrong app. ;)

For fun, play train + airplane at the same time. Train in the sky.