Installing

1. Download the .zip file and extract the addons folder to your root project folder res://
2. Enable the addon by ticking the enable checkbox at Project -> Project Settings -> addons

About

This is a simple barebones FSM project, it contains a FSM brain and State class so you can focus on building your states and logic.

The state machine is not limited to player nor enemy logic, it's parent agnostic, meaning that you have to define manually the component that its gonna alter, here a quick example of a Idle state for a CharacterBody3D (player):

extends State
class_name player_idle

@export var player_character: CharacterBody3D
var gravity: float = ProjectSettings.get_setting("physics/3d/default_gravity")

func Physics_Process(_delta: float) -> void:
    if !player_character.is_on_floor():
        change_state.emit(self, "player_falling")
        pass
    
    if Input.is_action_just_pressed("backward") or Input.is_action_just_pressed("forward") or Input.is_action_just_pressed("left") or Input.is_action_just_pressed("right"):
        change_state.emit(self, "player_moving")
    
    player_character.velocity.x = 0
    player_character.velocity.z = 0
    
    player_character.move_and_slide()
    pass

Creating a new State

Changing States

To change between states is simple as calling the change_state signal, it takes two arguments, the state emmiting the signal and the desired state:

change_state.emit(self, "your_new_state")