Creating AI for Enemies in a 2D Godot Platformer Game

Welcome back to our game development blog! Today, we’re tackling an exciting topic: creating AI for enemies in a 2D platformer game using Godot. AI can greatly enhance the gameplay experience by providing challenging and dynamic interactions. In this tutorial, we’ll cover the basics of setting up enemy AI, including patrolling, chasing the player, and attacking.


Setting Up the Project


Before we dive into the AI, let’s set up a basic project in Godot:


1. Create a New Project

• Open Godot and create a new project. Name it something like “EnemyAITutorial”.

2. Set Up the Scene

• Create a new 2D scene and add a KinematicBody2D node. This will be our enemy node.

• Add a Sprite and CollisionShape2D as children of the KinematicBody2D node to represent the enemy visually and physically.

• Save the scene as Enemy.tscn.


Step 1: Basic Enemy Movement


We’ll start by making the enemy move back and forth (patrolling):


1. Attach a Script to the Enemy

• Select the KinematicBody2D node and attach a new script named Enemy.gd.

2. Define Movement Variables

• In the script, define variables for speed and direction:


extends KinematicBody2D


# Movement Variables

var speed = 100

var direction = Vector2(-1, 0)  # Start moving left

var patrol_distance = 200

var start_position


func _ready():

    start_position = position


func _physics_process(delta):

    patrol()


3. Implement Patrolling Logic

• Add a function to handle the patrolling movement:


func patrol():

    position += direction * speed * get_physics_process_delta_time()


    # Reverse direction if patrol distance is exceeded

    if position.distance_to(start_position) > patrol_distance:

        direction *= -1


Step 2: Adding Player Detection


Next, we’ll add functionality for the enemy to detect the player and switch to a chasing state:


1. Player Detection Area

• Add an Area2D node as a child of the KinematicBody2D node, and name it DetectionArea.

• Add a CollisionShape2D to the Area2D node to define the detection range.

2. Connect Signals

• Connect the body_entered and body_exited signals of the Area2D node to the enemy script.

3. Handle Player Detection

• Update the script to handle player detection:


var player_detected = false

onready var detection_area = $DetectionArea


func _ready():

    start_position = position

    detection_area.connect("body_entered", self, "_on_DetectionArea_body_entered")

    detection_area.connect("body_exited", self, "_on_DetectionArea_body_exited")


func _physics_process(delta):

    if player_detected:

        chase_player()

    else:

        patrol()


func _on_DetectionArea_body_entered(body):

    if body.name == "Player":

        player_detected = true


func _on_DetectionArea_body_exited(body):

    if body.name == "Player":

        player_detected = false


Step 3: Implementing Chasing Behavior


Now we’ll implement the chasing behavior:


1. Chasing Logic

• Add a function to handle chasing the player:


var player


func chase_player():

    if player == null:

        return

    

    var direction_to_player = (player.position - position).normalized()

    move_and_slide(direction_to_player * speed)


func _on_DetectionArea_body_entered(body):

    if body.name == "Player":

        player_detected = true

        player = body


func _on_DetectionArea_body_exited(body):

    if body.name == "Player":

        player_detected = false

        player = null


Step 4: Adding Attack Behavior


Finally, we’ll add the ability for the enemy to attack the player when in close range:


1. Attack Area

• Add another Area2D node as a child of the KinematicBody2D node, and name it AttackArea.

• Add a CollisionShape2D to the Area2D node to define the attack range.

2. Connect Attack Signals

• Connect the body_entered signal of the AttackArea node to the enemy script.

3. Handle Attacking

• Update the script to handle attacking:


var attack_cooldown = 1.0

var time_since_last_attack = 0.0

onready var attack_area = $AttackArea


func _ready():

    start_position = position

    detection_area.connect("body_entered", self, "_on_DetectionArea_body_entered")

    detection_area.connect("body_exited", self, "_on_DetectionArea_body_exited")

    attack_area.connect("body_entered", self, "_on_AttackArea_body_entered")


func _physics_process(delta):

    if player_detected:

        chase_player()

        if time_since_last_attack >= attack_cooldown:

            attack()

    else:

        patrol()


    time_since_last_attack += delta


func attack():

    if player == null:

        return

    

    player.take_damage(10)  # Assuming the player has a take_damage method

    time_since_last_attack = 0.0


func _on_AttackArea_body_entered(body):

    if body.name == "Player":

        attack()


Conclusion


You’ve successfully implemented basic AI for enemies in a 2D Godot platformer game! Your enemies can now patrol, detect the player, chase them, and attack when in range. From here, you can expand on this AI by adding more sophisticated behaviors, such as jumping, ranged attacks, or working in groups.


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Summary of Steps


1. Set Up the Project: Create a new project and set up the enemy scene.

2. Basic Enemy Movement: Implement patrolling behavior.

3. Adding Player Detection: Add player detection using an Area2D node.

4. Implementing Chasing Behavior: Make the enemy chase the player when detected.

5. Adding Attack Behavior: Allow the enemy to attack the player when in close range.


Happy developing!

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