Heh, I always get those two crates names confused, even now, rereading comments I again thought it was "clap" and not "cpal" (because "clap" like in "clapping").
But I feel like there's some deeper story about Rust that I've missed and am out of the loop now.
Well, to me Rust is just a tool that I've discovered, it meet my expectations so I started using it.
Only then I've started noticing comments on reddit or whatever like "bleh, not Rust again" and really don't get why a programming language can be so triggering to people.
Performance reasons, also wanted it to work on the web (Flutter web support is fairly recent, and dart/flutter libraries don't automatically work on the web, they have to support the platform).
Well, all the Rust crates I've mentioned in other comment have comprehensive examples attached, so it's just a matter of connecting their functionality together :)
If web - well, it sadly requires modern browser on relatively modern hardware - it has some performance problems currently in browsers, I'm not happy about that fact, I am considering improving it if the app catches enough interest.
If Android - please consider returning the app and getting your money back as long as you still can - I'm afraid I won't be able to solve it in quick fashion.
I'm planning to create a simpler free version of the app for the sake of cross-promotion, I may open source that one (but I can't make any promises currently, both regarding creating the actual app and open sourcing it).
It's available free (and no ads) for desktop browsers and as a $1 Android app (on mobile needs to be an app for performance reasons and I believe it's a fair price).