^ My guess:
Some programmers were mucking around with a physics engine. They ported it to iOS. They got tired of dropping balls onto the stacks of objects and thought about how to have fun. A slingshot of course!
Then they hired some artists to make it more appealing, and ****s me how why but the decided to make the ball into some birds. And the aim was to hit pigs hiding under their little physics experiment.
Basically the artists made the game more appealing, and more confusing, at the same time.
If you want to have a quick and simple play with your own physics engine there's a fantastic tutorial here:
burakkanber.com/blog/modeling-physics-javascript-gravity-and-drag/You can write it yourself, runs in a browser.
The results are at the bottom of the tutorial. the
JSFiddle box. Click 'results'.
If you read the above tutorial, very carefully and slowly, you should be able to understand it, or at least most of it, using only primary school mathematics and some imagination. OK, at least the gist of it.
