Initialization of the view.
Fixed typo
Initialize the game scene and present it
Added player variable
Variable for how many aliends have been destroyed
Added variables for deciding when to add new aliens in the game scene
Overriding the init method
Initialize the background with a black color
Initialize the player
Added the player to the game scene
Removed the gravity from the physicsWorld
Extend the GameScene with the SKPhysicsContactDelegate. It will be used for collision detection
Added contact delegate for the physics world