Create a new script called EnemyBehaviour.

We want our enemy to follow the player if they get too close to them; however, they will stay where they are if the player gets far enough away. Finally, if, for some reason, we defeat the enemy, they should no longer run this behavior, and we should kill them. The first step to creating a state machine is to extract the states that the object can be in. In this case, we have three states: Idle, Following, and Death. Just as we discussed in Chapter 2, Creating GUIs, using an enumeration is the best tool for the job here as well.

Add the following code to the top of the EnemyBehaviour class:

   public enum State 
  {
    Idle,
    Follow,
    Die,
  }

   // The current state the player is in
  public State state...