Just wondered about app sizes.

Smallest I have seen is MysticalColors at 145kb

I think a better question would be, what's the smallest Corona app?
It seems there is around 4MB of overhead in most of my Corona apps, regardless of assets/code.

4mb?
well that ain't gunna break any records.

I once, before building my app, deleted all the @2x images and unnecessary images. (Since i was still making it)

After building the size was 3.7 MB big.

After doing a tiny bit of coding the next day i rebuilt it and thought i deleted the same files.

This time it was 11.7 MB

I don't understand it but oh well.