Project Setup and 2D Physics Foundation

Welcome to the first lesson of Building a Flappy Bird Clone. In this module, we will establish the foundational architecture of our game. Flappy Bird relies on precise, snappy 2D physics rather than realistic momentum. We will use a CharacterBody2D for complete control over our bird's gravity and jump mechanics.

We will be using Godot 4 and its 2D engine to build this core system.

1. Environment and Project Initialization#

First, create a new Godot 4 project. Let's establish a clean directory structure for our assets and scenes.

Create the following folders in your res:// directory:

• 📁 Assets/ (For sprites and audio)
• 📁 Scenes/ (For levels and UI screens)
• 📁 Entities/ (For our Bird and Pipes)
• 📁 Scripts/ (For global autoloads)

Configuring Display Settings#

Flappy Bird is a portrait-oriented game. We need to adjust our window size.

1. Navigate to Project > Project Settings.
2. Go to Display > Window.
3. Under Size, set Viewport Width to 480 and Viewport Height to 854.
4. Set Stretch Mode to canvas_items and Aspect to keep so the game scales cleanly on different monitors.

Input Mapping#

We need to map our flap control. In Project Settings > Input Map, add a new action:

• flap (Assign this to Spacebar and Left Mouse Button)

2. Constructing the Bird Entity#

Create a new scene with a CharacterBody2D as the root node and name it Bird. This node is ideal because it gives us absolute control over vertical velocity without fighting an automated physics engine.

• 🐦 Bird (CharacterBody2D)
  • 🟩 BirdSprite (Sprite2D - Add a simple placeholder texture for now)
  • 🟢 CollisionShape2D (Use a CircleShape2D and match it to your sprite)

3. The Flap Controller Script#

Attach a new GDScript to the Bird root node. We will use _physics_process to apply gravity consistently and listen for our flap input.

extends CharacterBody2D
class_name Bird

@export var jump_velocity: float = -400.0
@export var rotation_speed: float = 2.0

# Get the gravity from the project settings to be synced with RigidBody nodes.
var gravity: float = ProjectSettings.get_setting("physics/2d/default_gravity")

func _ready() -> void:
	# Ensure the bird starts with zero velocity
	velocity = Vector2.ZERO

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

	# 2. Handle Flap Input
	if Input.is_action_just_pressed("flap"):
		# Directly set velocity.y to instantly cancel downward momentum
		velocity.y = jump_velocity

	# 3. Apply Movement
	move_and_slide()
	
	# 4. Polish: Add visual tilt based on vertical velocity
	if velocity.y < 0:
		# Flapping up: tilt upwards
		rotation = lerp_angle(rotation, deg_to_rad(-30), rotation_speed * delta * 5.0)
	else:
		# Falling: tilt downwards
		rotation = lerp_angle(rotation, deg_to_rad(90), rotation_speed * delta)