add-mechanic

Add Mechanic

Add game mechanics using correct GDScript 4.x syntax. Prevents common LLM mistakes with outdated GDScript 3.x patterns.

GDScript 4.x Syntax Rules

These changed from Godot 3 to 4. LLMs frequently generate the OLD syntax:

Correct (GDScript 4.x)	Wrong (GDScript 3.x -- will error)
@export var speed: float = 200.0	export var speed = 200.0
@onready var sprite = $Sprite2D	onready var sprite = $Sprite2D
signal health_changed(new_hp: int)	signal health_changed (no typed params)
func _ready() -> void:	func _ready(): (return type optional but preferred)
velocity = Vector2(...) then move_and_slide()	move_and_slide(velocity, Vector2.UP) (args removed in 4.x)
super()	.method() for parent calls
await get_tree().create_timer(1.0).timeout	yield(get_tree().create_timer(1.0), "timeout")
%UniqueNode	get_node("path/to/node") when unique name is set

Movement Patterns

Platformer Movement

extends CharacterBody2D

@export var speed: float = 300.0
@export var jump_velocity: float = -400.0
@export var gravity: float = 980.0

func _physics_process(delta: float) -> void:
    # Gravity
    if not is_on_floor():
        velocity.y += gravity * delta

    # Jump
    if Input.is_action_just_pressed("jump") and is_on_floor():
        velocity.y = jump_velocity

    # Horizontal movement
    var direction := Input.get_axis("move_left", "move_right")
    velocity.x = direction * speed

    move_and_slide()

Key: move_and_slide() takes NO arguments in Godot 4. Velocity is set on the velocity property directly.

Top-Down Movement

extends CharacterBody2D

@export var speed: float = 200.0

func _physics_process(_delta: float) -> void:
    var direction := Input.get_vector("move_left", "move_right", "move_up", "move_down")
    velocity = direction * speed
    move_and_slide()

Point-and-Click Movement

extends CharacterBody2D

@export var speed: float = 200.0
var target_position: Vector2

func _input(event: InputEvent) -> void:
    if event is InputEventMouseButton and event.pressed:
        target_position = get_global_mouse_position()

func _physics_process(_delta: float) -> void:
    if position.distance_to(target_position) > 5.0:
        velocity = position.direction_to(target_position) * speed
    else:
        velocity = Vector2.ZERO
    move_and_slide()