7MB is about the base size for an APK.
My current project is about 3,000 lines and the APK is 7,614MB.
The extra weight is the engine beneath your code, that converts our simple sprite creations into OpenGL commands, for example.
Quote: "Is there a way to reduce the apk size?"
I don't know the answer but I imagine that it contains everything needed for all APK platforms (e.g Google Play, Amazon). Maybe it could be smaller for a single-market release, let's hope somebody with more technical knowledge sees this thread, I'm interested too.
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