Show HN: Fluid Simulation that I created. Any tips for improvement

I think you should at least include a Youtube video, so anyone who doesn’t have an Android device (and don’t want to download a whole app to see a tech demo) can look at it.

allow users to record a small gif and post it somewhere

Generic, there are tons of apps like that, also looks like you just used some library.

I am not downloading an app to give you feedback.

Instead of giving the direct link, I would have appreciated a website that has screenshots, use examples, some form of documentation, etc.

If it were OSS, I would have liked a link to the repo.

If some of the conditions were met, I might have downloaded and tried the app.