The player has now left the game. This is indicated by setting the optional playerOne
variable to nil, meaning “no Player instance.” At the point that this happens, the playerOne
variable’s reference to the Player instance is broken. No other properties or variables are
still referring to the Player instance, and so it is deallocated in order to free up its memory.
Just before this happens, its deinitializer is called automatically, and its coins are returned
to the bank.