SKILL.md

Godot GDScript Patterns

Name: godot-gdscript-patterns
Author: wshobson

Production patterns for Godot 4.x game development with GDScript, covering architecture, signals, scenes, and optimization.

When to Use This Skill

Building games with Godot 4

Implementing game systems in GDScript

Designing scene architecture

Managing game state

Optimizing GDScript performance

Learning Godot best practices

Core Concepts

1. Godot Architecture

Node: Base building block

├── Scene: Reusable node tree (saved as .tscn)

├── Resource: Data container (saved as .tres)

├── Signal: Event communication

└── Group: Node categorization

2. GDScript Basics

class_name Player

extends CharacterBody2D

# Signals

signal health_changed(new_health: int)

signal died

# Exports (Inspector-editable)

@export var speed: float = 200.0

@export var max_health: int = 100

@export_range(0, 1) var damage_reduction: float = 0.0

@export_group("Combat")

@export var attack_damage: int = 10

@export var attack_cooldown: float = 0.5

# Onready (initialized when ready)

@onready var sprite: Sprite2D = $Sprite2D

@onready var animation: AnimationPlayer = $AnimationPlayer

@onready var hitbox: Area2D = $Hitbox

# Private variables (convention: underscore prefix)

var _health: int

var _can_attack: bool = true

func _ready() -> void:

    _health = max_health

func _physics_process(delta: float) -> void:

    var direction := Input.get_vector("left", "right", "up", "down")

    velocity = direction * speed

    move_and_slide()

func take_damage(amount: int) -> void:

    var actual_damage := int(amount * (1.0 - damage_reduction))

    _health = max(_health - actual_damage, 0)

    health_changed.emit(_health)

    if _health <= 0:

        died.emit()

Patterns

Pattern 1: State Machine

# state_machine.gd

class_name StateMachine

extends Node

signal state_changed(from_state: StringName, to_state: StringName)

@export var initial_state: State

var current_state: State

var states: Dictionary = {}

func _ready() -> void:

    # Register all State children

    for child in get_children():

        if child is State:

            states[child.name] = child

            child.state_machine = self

            child.process_mode = Node.PROCESS_MODE_DISABLED

    # Start initial state

    if initial_state:

        current_state = initial_state

        current_state.process_mode = Node.PROCESS_MODE_INHERIT

        current_state.enter()

func _process(delta: float) -> void:

    if current_state:

        current_state.update(delta)

func _physics_process(delta: float) -> void:

    if current_state:

        current_state.physics_update(delta)

func _unhandled_input(event: InputEvent) -> void:

    if current_state:

        current_state.handle_input(event)

func transition_to(state_name: StringName, msg: Dictionary = {}) -> void:

    if not states.has(state_name):

        push_error("State '%s' not found" % state_name)

        return

    var previous_state := current_state

    previous_state.exit()

    previous_state.process_mode = Node.PROCESS_MODE_DISABLED

    current_state = states[state_name]

    current_state.process_mode = Node.PROCESS_MODE_INHERIT

    current_state.enter(msg)

    state_changed.emit(previous_state.name, current_state.name)

# state.gd

class_name State

extends Node

var state_machine: StateMachine

func enter(_msg: Dictionary = {}) -> void:

    pass

func exit() -> void:

    pass

func update(_delta: float) -> void:

    pass

func physics_update(_delta: float) -> void:

    pass

func handle_input(_event: InputEvent) -> void:

    pass

# player_idle.gd

class_name PlayerIdle

extends State

@export var player: Player

func enter(_msg: Dictionary = {}) -> void:

    player.animation.play("idle")

func physics_update(_delta: float) -> void:

    var direction := Input.get_vector("left", "right", "up", "down")

    if direction != Vector2.ZERO:

        state_machine.transition_to("Move")

func handle_input(event: InputEvent) -> void:

    if event.is_action_pressed("attack"):

        state_machine.transition_to("Attack")

    elif event.is_action_pressed("jump"):

        state_machine.transition_to("Jump")

Pattern 2: Autoload Singletons

# game_manager.gd (Add to Project Settings > Autoload)

extends Node

signal game_started

signal game_paused(is_paused: bool)

signal game_over(won: bool)

signal score_changed(new_score: int)

enum GameState { MENU, PLAYING, PAUSED, GAME_OVER }

var state: GameState = GameState.MENU

var score: int = 0:

    set(value):

        score = value

        score_changed.emit(score)

var high_score: int = 0

func _ready() -> void:

    process_mode = Node.PROCESS_MODE_ALWAYS

    _load_high_score()

func _input(event: InputEvent) -> void:

    if event.is_action_pressed("pause") and state == GameState.PLAYING:

        toggle_pause()

func start_game() -> void:

    score = 0

    state = GameState.PLAYING

    game_started.emit()

func toggle_pause() -> void:

    var is_paused := state != GameState.PAUSED

    if is_paused:

        state = GameState.PAUSED

        get_tree().paused = true

    else:

        state = GameState.PLAYING

        get_tree().paused = false

    game_paused.emit(is_paused)

func end_game(won: bool) -> void:

    state = GameState.GAME_OVER

    if score > high_score:

        high_score = score

        _save_high_score()

    game_over.emit(won)

func add_score(points: int) -> void:

    score += points

func _load_high_score() -> void:

    if FileAccess.file_exists("user://high_score.save"):

        var file := FileAccess.open("user://high_score.save", FileAccess.READ)

        high_score = file.get_32()

func _save_high_score() -> void:

    var file := FileAccess.open("user://high_score.save", FileAccess.WRITE)

    file.store_32(high_score)

# event_bus.gd (Global signal bus)

extends Node

# Player events

signal player_spawned(player: Node2D)

signal player_died(player: Node2D)

signal player_health_changed(health: int, max_health: int)

# Enemy events

signal enemy_spawned(enemy: Node2D)

signal enemy_died(enemy: Node2D, position: Vector2)

# Item events

signal item_collected(item_type: StringName, value: int)

signal powerup_activated(powerup_type: StringName)

# Level events

signal level_started(level_number: int)

signal level_completed(level_number: int, time: float)

signal checkpoint_reached(checkpoint_id: int)

Pattern 3: Resource-based Data

# weapon_data.gd

class_name WeaponData

extends Resource

@export var name: StringName

@export var damage: int

@export var attack_speed: float

@export var range: float

@export_multiline var description: String

@export var icon: Texture2D

@export var projectile_scene: PackedScene

@export var sound_attack: AudioStream

# character_stats.gd

class_name CharacterStats

extends Resource

signal stat_changed(stat_name: StringName, new_value: float)

@export var max_health: float = 100.0

@export var attack: float = 10.0

@export var defense: float = 5.0

@export var speed: float = 200.0

# Runtime values (not saved)

var _current_health: float

func _init() -> void:

    _current_health = max_health

func get_current_health() -> float:

    return _current_health

func take_damage(amount: float) -> float:

    var actual_damage := maxf(amount - defense, 1.0)

    _current_health = maxf(_current_health - actual_damage, 0.0)

    stat_changed.emit("health", _current_health)

    return actual_damage

func heal(amount: float) -> void:

    _current_health = minf(_current_health + amount, max_health)

    stat_changed.emit("health", _current_health)

func duplicate_for_runtime() -> CharacterStats:

    var copy := duplicate() as CharacterStats

    copy._current_health = copy.max_health

    return copy

# Using resources

class_name Character

extends CharacterBody2D

@export var base_stats: CharacterStats

@export var weapon: WeaponData

var stats: CharacterStats

func _ready() -> void:

    # Create runtime copy to avoid modifying the resource

    stats = base_stats.duplicate_for_runtime()

    stats.stat_changed.connect(_on_stat_changed)

func attack() -> void:

    if weapon:

        print("Attacking with %s for %d damage" % [weapon.name, weapon.damage])

func _on_stat_changed(stat_name: StringName, value: float) -> void:

    if stat_name == "health" and value <= 0:

        die()

Pattern 4: Object Pooling

# object_pool.gd

class_name ObjectPool

extends Node

@export var pooled_scene: PackedScene

@export var initial_size: int = 10

@export var can_grow: bool = true

var _available: Array[Node] = []

var _in_use: Array[Node] = []

func _ready() -> void:

    _initialize_pool()

func _initialize_pool() -> void:

    for i in initial_size:

        _create_instance()

func _create_instance() -> Node:

    var instance := pooled_scene.instantiate()

    instance.process_mode = Node.PROCESS_MODE_DISABLED

    instance.visible = false

    add_child(instance)

    _available.append(instance)

    # Connect return signal if exists

    if instance.has_signal("returned_to_pool"):

        instance.returned_to_pool.connect(_return_to_pool.bind(instance))

    return instance

func get_instance() -> Node:

    var instance: Node

    if _available.is_empty():

        if can_grow:

            instance = _create_instance()

            _available.erase(instance)

        else:

            push_warning("Pool exhausted and cannot grow")

            return null

    else:

        instance = _available.pop_back()

    instance.process_mode = Node.PROCESS_MODE_INHERIT

    instance.visible = true

    _in_use.append(instance)

    if instance.has_method("on_spawn"):

        instance.on_spawn()

    return instance

func _return_to_pool(instance: Node) -> void:

    if not instance in _in_use:

        return

    _in_use.erase(instance)

    if instance.has_method("on_despawn"):

        instance.on_despawn()

    instance.process_mode = Node.PROCESS_MODE_DISABLED

    instance.visible = false

    _available.append(instance)

func return_all() -> void:

    for instance in _in_use.duplicate():

        _return_to_pool(instance)

# pooled_bullet.gd

class_name PooledBullet

extends Area2D

signal returned_to_pool

@export var speed: float = 500.0

@export var lifetime: float = 5.0

var direction: Vector2

var _timer: float

func on_spawn() -> void:

    _timer = lifetime

func on_despawn() -> void:

    direction = Vector2.ZERO

func initialize(pos: Vector2, dir: Vector2) -> void:

    global_position = pos

    direction = dir.normalized()

    rotation = direction.angle()

func _physics_process(delta: float) -> void:

    position += direction * speed * delta

    _timer -= delta

    if _timer <= 0:

        returned_to_pool.emit()

func _on_body_entered(body: Node2D) -> void:

    if body.has_method("take_damage"):

        body.take_damage(10)

    returned_to_pool.emit()

Pattern 5: Component System

# health_component.gd

class_name HealthComponent

extends Node

signal health_changed(current: int, maximum: int)

signal damaged(amount: int, source: Node)

signal healed(amount: int)

signal died

@export var max_health: int = 100

@export var invincibility_time: float = 0.0

var current_health: int:

    set(value):

        var old := current_health

        current_health = clampi(value, 0, max_health)

        if current_health != old:

            health_changed.emit(current_health, max_health)

var _invincible: bool = false

func _ready() -> void:

    current_health = max_health

func take_damage(amount: int, source: Node = null) -> int:

    if _invincible or current_health <= 0:

        return 0

    var actual := mini(amount, current_health)

    current_health -= actual

    damaged.emit(actual, source)

    if current_health <= 0:

        died.emit()

    elif invincibility_time > 0:

        _start_invincibility()

    return actual

func heal(amount: int) -> int:

    var actual := mini(amount, max_health - current_health)

    current_health += actual

    if actual > 0:

        healed.emit(actual)

    return actual

func _start_invincibility() -> void:

    _invincible = true

    await get_tree().create_timer(invincibility_time).timeout

    _invincible = false

# hitbox_component.gd

class_name HitboxComponent

extends Area2D

signal hit(hurtbox: HurtboxComponent)

@export var damage: int = 10

@export var knockback_force: float = 200.0

var owner_node: Node

func _ready() -> void:

    owner_node = get_parent()

    area_entered.connect(_on_area_entered)

func _on_area_entered(area: Area2D) -> void:

    if area is HurtboxComponent:

        var hurtbox := area as HurtboxComponent

        if hurtbox.owner_node != owner_node:

            hit.emit(hurtbox)

            hurtbox.receive_hit(self)

# hurtbox_component.gd

class_name HurtboxComponent

extends Area2D

signal hurt(hitbox: HitboxComponent)

@export var health_component: HealthComponent

var owner_node: Node

func _ready() -> void:

    owner_node = get_parent()

func receive_hit(hitbox: HitboxComponent) -> void:

    hurt.emit(hitbox)

    if health_component:

        health_component.take_damage(hitbox.damage, hitbox.owner_node)

For advanced Godot patterns, performance tips, and best practices, see references/advanced-patterns.md:

Pattern 6: Scene Management — Autoload SceneManager with async threaded loading (ResourceLoader.load_threaded_request), ResourceLoader.has_cached check, transition overlay support, and scene swapping with queue_free

Pattern 7: Save System — Autoload SaveManager with AES-encrypted save files (FileAccess.open_encrypted_with_pass), JSON serialization, and a reusable Saveable component node for per-node save/load lifecycle

Performance Tips — caching @onready references, avoiding allocations in _process, static typing benefits, disabling processing for off-screen nodes

Best Practices — Do's and Don'ts covering signals, typing, resources, pooling, and Autoloads

godot-gdscript-patterns