A common strategy in game play programming (and computer science in general) is to model a system in terms of discrete objects and their interactions with one another. To do this requires us to understand what the participants are in a system, how they operate in different scenarios, and how they change states.

The Finite State Machine (FSM) is one such technique. With this, the idea is to model the behavior of the object in a number of code blocks. Inside each one, you put the specific code for that block that makes it unique. You also determine what scenarios cause an object to switch from one block (state) to another. Because each state is an encapsulation, it makes your code extensible and maintainable (which is a great thing!).