Screen ratio for mobile devices.

I am new to mobile development and wanted to develop a game for android, but I face the problem of screen resolution.

I want my game to run on multiple phones with a resolution that doesn't have any missing parts on the screen.

how can i develop like this?

can you send me if possible in addition to the explanation any example of C2 that you have to help me?

it doesn't exist one resolution that fits all screens.

but just use scale outer, if you are annoyed by black borders