We'll need a GameStateManager, and an abstract GameState class.

*GameState must have a subclass for each game state
*Each state (Intro, etc.) holds whatever objects are relevant.
*GameStateManager must handle transitions.
*Each state must have virtual method for input(), logic(), render(), and a bool "willChange" that if true calls changeState
*States will be represented by an enum class
*Objects must be destroyed when the state ends