Finally coming back to this after having it open in a tab for months, lol
I have two bits of feedback. One is that some sounds might be better as one-offs that automatically just play once, rather than being a continuous loop. The rainstorm and forest sounds are good loops, but a lightning strike or gunshot might make more sense as single presses.
Kinda related, I can’t imagine it makes much sense to play two music tracks at once. Switching between them might make more sense as a radio button type experience rather than a checkbox.
Other than that though, this is great. Really simple to use and very clear, but with a great range of options.