Buddy super mario bros was coded in 6502 assembly and required the devs to use every data saving trick in the book like metasprites, sprite flicker, tilesets, color pallets, etc.
Android apps can be notoriously overhead bloat from Java, so for the modern age this is decently impressive.
Android has a massive built-in library of supporting functions that abstracts away most of the differences between devices, including support libraries for older versions of Android, and Flappy Bird is almost the "hello world" of gamws writing.