A few years back I wanted to experiment with Android programming, so I wrote the simplest app I could think of...a Tip Calculator. It's often my go to for new programming languages. It's really basic, I'm sure you can find a dozen more that are way better. That said I'm putting it here, you're welcome to download it and use it for free....but totally at your own risk. This was written for an old version of Android and there won't be any updates ever. I have tried it on Android 11 and it seems to work fine. But again, use this totally at your own risk. If it bricks your phone don't call me.
Oh and one last thing....you'll have to sideload the apk. I don't have plans to put it on any app store.Download Tip Calculator for Andriod APK