I wrote "just use a match statement, it's fine" three times before I stopped saying it. It is fine, right up until an enemy needs a fourth state and two of the transitions start depending on each other. Here is what actually cost time building enemy AI for a wave-based game, in the order it bit me. Lesson 1: the match statement is fine until state 4 A two-state enemy — chase, attack — is genuinely not worth a framework: func _physics_process ( delta : float ) ...