I just built my first android app. A scientific calculator. Once installed I thought of checking it's size and comparing it with similar apps. My app is 650kb, the most popular currently on the play store is 500kb and the default one is 4kb.
My app has only one activity, with a class and layout which before compiling are 20kb together. So how can my app be taking 100kb more than the most popular one? I'm just curious, I suppose there are files generated authomatically that can be eliminated to save space (like some images I found inside /res) but cannot just delete files randomly.
What can I do to make the app lighter? How can I check which files are unused?