What is the secret of the small android build?

Question

Android

How to make a game on android with a size of 1 megabyte? For example, Flappy Bird weighed even less. Then in the app store, in the "if memory runs out" section, there are small applications, for example, a sandbox and chess, the size is slightly more than 2 mb.
Are there any ready-made solutions? The best thing I've seen is the defold engine, an empty build weighs 1.3, let's keep silent about all sorts of units

Answer 1

https://m.habr.com/en/post/339938/
I made 77 Kb apk.
But I did not go deeper, although it could be further reduced.
The main volume is unnecessary resources and unnecessary libraries.