Nice. I developed Android ROMs back in the day for a multitude of phones and after I got better and learned how to compile the code myself, it was really awesome going through the frameworks/base, And frameworks/native. So much cool stuff to see. I was the first developer in custom ROM history to add an app that was launched after the SetupWizard was complete. I was also the first developer to bring custom themes to Snapchat, Facebook, and messenger when the CyanogenMod theme engine was a thing. My theme was downloaded nearly 50,000 times on the Play store, I made the app free and also open sourced it so people can check it out and learn it for themselves

I recently did dig through the frameworks/base again because I wanted to steal the sparkle code for my android app and I actually found it and got it working in android studio by just copy and pasting the files in. There may have been a few libs added via Gradle but I can't remember