Let's kick-start the game by implementing the background, which is not as straightforward as it might sound.
SpriteKit is a powerful, but easy-to-use, game framework introduced in iOS 7.
It basically provides the infrastructure to move images onto the screen and interact with them.
It also provides a physics engine (based on Box2D), a particles engine, and basic sound playback support, making it particularly suitable for casual games.
The content of the game is drawn inside an
SKView, which is a particular kind of
UIView, so it can be placed inside a normal hierarchy of UIViews.
The content of the game is organized into scenes, represented by subclasses of
SKScene. Different parts of the game, such as the menu, ...