np5dias, hi.
First, let’s start with the easy one. You can add more balls by adjusting level files.
https://github.com/coronalabs-samples/CoronaCannon/tree/master/levels
Open them and add more elements to the ammo table. Values are either ‘normal’ or ‘bomb’.
As you can see, it controls not only the amount of balls, but also their sequence.
Zoom, on the other hand, is very tricky. I decided not to include the zoom logic into the game, because it greatly complicates the code.
You can add a new field to self.camera, something like self.camera.zoom and depending on that value you adjust the scale AND position of self.group. It’s quite tricky, but that’s enough to get going.
https://github.com/coronalabs-samples/CoronaCannon/blob/master/libs/tiled.lua