Now that you've built the app, it's time to customise it to make it your own.
There's a large collection of free sounds at https://freesound.org/
You can download collections of various sounds, e.g. birds/fart sounds/atmospheric sounds.
Maybe you'll want to build a personal sound track to turn your life into a movie. Want to investigate a strange movement in your backyard? Click on the tense string ensemble. Hit with a flash of inspiration? Click on the corresponding sound effect.
Perhaps a bit too much of a narcissistic app idea, I'll leave you to come up with the ideas to customise the app.
If you build something cool, I'd love to know about it. Share a preview video on Twitter with the hashtag #FlutterBrew to show it off!