JVDesignStudio · Godot 4 Tutorial

Build
Space Invaders
From Scratch

📦

Starter template: download the ready-to-open Godot 4 Space Invaders project this workshop builds: ⬇ space_invaders.zip.

A coding adventure for kids aged 8 and up. 11 chapters. Real GDScript. A complete, playable game by the end, and you write every line yourself.

Godot 4 GDScript 📚 11 Chapters 🆓 Free Ages 8+

🚀 Start Building 📖 Godot Beginner Guide

EngineGodot 4

LanguageGDScript

Chapters11

Aliens55

Ages8+

PriceFree

🎯 What You'll Build

A Complete Space Invaders Clone

By the end of Chapter 10 you'll have a fully playable game. Every feature, written by you.

👾

55 Alien Formation

A grid of aliens that march left and right, drop down, and speed up as you shoot them.

🚀

Player Spaceship

A ship you control with the keyboard move left, right, and fire bullets at the aliens.

🛡️

Four Shields

Destructible barriers you can hide behind both your bullets and alien bullets chip them away.

💥

Explosions

Animated pixel-art explosions when aliens and the player ship get hit.

📊

Lives & Score

Three lives, a live score counter, and a hi-score that persists across waves.

🎮

Endless Waves

Each wave resets the aliens faster the game gets harder until you run out of lives.

📋 Before You Start

How to Use This Guide

Do one chapter at a time. Test after each one. Don't skip ahead. This is how real programmers work.

✅ DO THIS

Numbered Steps

Follow these in order. Always complete every step before moving on don't skip.

✅ Checkpoint

Check Your Work

At the end of each chapter, verify these things in Godot before moving on.

💡 Tip

Helpful Hints

Shortcuts, tricks, and things that make the next step easier to understand.

⚠️ Watch Out

Common Mistakes

Things that trip people up. Read these carefully they'll save you time.

ℹ️ Info

Concept Explainers

Plain-English explanations of a tricky idea before you need to use it.

Rule #1

Type the Code Yourself

Don't copy-paste. Your fingers learn coding like they learn piano by doing it.

📖 The Guide

11 Chapters

Start at Chapter 1 and work through in order. Each chapter adds one piece to the game.

Chapter 1 · Setup

Setting Up Godot

Godot is a free program that turns your code into a real game. It handles the window, graphics, sounds all the boring stuff. You focus on the fun part: telling the game what to DO.

Go to godotengine.org → Download Godot 4 for your computer → Open it
In the Project Manager, click New Project ? name it "Space Invaders" ? Click Create & Edit
Click Project → Project Settings → Display → Window → Set width to 480, height to 600, Stretch Mode to canvas_items

Godot is open · Project "Space Invaders" exists · Window is 480×600

Godot 4Project Setup480×600

What does setting Stretch Mode to canvas_items do?

Chapter 2 · Game State

The Game State Script

Before building anything visible, create a script that remembers the score, lives, and wave number. This is called GameState.

A normal script only works while its scene is open. An Autoload script runs all the time, forever. Perfect for score and lives, because they need to survive scene changes.

# GameState.gd, type this exactly
extends Node

# var creates a variable, a box that holds a number
var score: int = 0
var lives: int = 3
var wave:  int = 1
var hi_score: int = 0

FileSystem panel ? right-click res:// ? New Script ? name it GameState.gd ? type the code above
Press Ctrl+S to save
Project ? Project Settings ? Autoload tab ? add GameState.gd ? click Add

GameState.gd saved · Appears in Autoload list · No red error lines

What is an Autoload in Godot?

Chapter 3 · Player Ship

The Player Ship

The player ship moves left/right and fires bullets. It's built from three nodes stacked together.

Three nodes needed: Area2D (the container, detects when things touch it), Sprite2D (shows the ship picture), CollisionShape2D (invisible hit shape).

Scene ? New Scene ? add Area2D root ? rename it "Player"
Add Sprite2D child ? add CollisionShape2D child ? set shape to RectangleShape2D
Save as Player.tscn ? attach a new script Player.gd

# Player.gd
extends Area2D
const SPEED = 180.0
const SCREEN_W = 480.0
var can_shoot = true

func _process(delta):
    var dir = int(Input.is_action_pressed("ui_right")) - int(Input.is_action_pressed("ui_left"))
    position.x = clamp(position.x + dir * SPEED * delta, 20, SCREEN_W - 20)
    if Input.is_action_just_pressed("ui_accept") and can_shoot:
        shoot()

Player.tscn and Player.gd saved · No red error lines

What does Input.get_axis() return?

Chapter 4 · Bullet

The Bullet Scene

Both the player and the aliens fire bullets. Build one bullet scene and reuse it for both, just change the direction.

# Bullet.gd
extends Area2D
# -1.0 = flies UP (player)  +1.0 = flies DOWN (enemy)
@export var direction: float = -1.0
@export var speed: float = 400.0
@export var is_enemy: bool = false

func _process(delta):
    position.y += speed * direction * delta
    # Delete bullet when it leaves the screen
    if position.y < -20 or position.y > 650:
        queue_free()

queue_free() tells Godot to delete this node safely at the end of the current frame, not immediately while the game is still using it.

Bullet.tscn and Bullet.gd saved · No errors

Why do we call queue_free()?

Chapter 5 · One Alien

The Alien Scene

Build a single alien scene. Later, the AlienGrid script will create 55 copies of it automatically.

Use AnimatedSprite2D (not Sprite2D), this one plays frame animations like a cartoon. You need 3 animations: 'a' (squid), 'b' (crab), 'c' (ufo). Each has 2 frames for walking.

# Alien.gd
extends Area2D
signal alien_killed(points, pos)
# 0=squid(10pts)  1=crab(20pts)  2=ufo-row(30pts)
@export var alien_type: int = 0
@export var points: int = 10

func _ready():
    add_to_group("aliens")
    match alien_type:
        0: $AnimatedSprite2D.play("a")
        1: $AnimatedSprite2D.play("b")
        2: $AnimatedSprite2D.play("c")

func die():
    alien_killed.emit(points, global_position)
    queue_free()

Alien.tscn and Alien.gd saved · No errors · Images set up in Chapter 8

What signal fires when two Area2D nodes overlap?

Chapter 6 · Alien Grid

The Alien Grid

The most complex script in the game. Take your time, read each section before typing it. AlienGrid does three jobs:

Fills the screen with 55 aliens (11 columns × 5 rows)
Marches them sideways, drops them down when they hit an edge
Picks a random alien at the bottom of each column to shoot at the player

# AlienGrid.gd, variables section
extends Node2D
signal all_dead
signal reached_bottom
signal enemy_bullet_fired(pos)

const COLS = 11
const ROWS = 5
const SPACING_X = 36
const SPACING_Y = 32
const ROW_POINTS = [30, 20, 20, 10, 10]
var _dir: float = 1.0
var _step_interval: float = 0.8
const AlienScene = preload("res://Alien.tscn")

This script has 5 parts. Type them in order, each part uses variables or functions from the part above it. Check for errors after each part.

preload() loads a scene when the game starts. Then AlienScene.instantiate() creates a new copy. Like a cookie cutter, load it once, stamp out as many as you need.

Why do the aliens speed up as you destroy them?

Chapter 7 · Barriers

Barriers & Explosions

Four destructible shields the player can hide behind. Both player and alien bullets chip chunks out of them.

Create a new scene ? StaticBody2D root ? rename "Barrier"
Add a Sprite2D child (your shield image) and a CollisionShape2D
Attach Barrier.gd, the script tracks health and destroys the node when it hits zero
Save as Barrier.tscn

Also create an Explosion scene, an AnimatedSprite2D that plays a short animation then deletes itself with queue_free().

# Barrier.gd, simplified
extends StaticBody2D
var health = 4

func take_hit():
    health -= 1
    # Update sprite to show damage
    $Sprite2D.frame = 4 - health
    if health <= 0:
        queue_free()

Barrier.tscn and Explosion.tscn saved · No errors

What happens when a Barrier's health reaches zero?

Chapter 8 · Sprites

Drawing the Sprites

Every game needs pictures. This chapter covers drawing your pixel art sprites and wiring them into the scenes.

Use any pixel art tool: Aseprite (paid, excellent), Piskel (free, browser-based), or LibreSprite (free desktop). Export each sprite as PNG with a transparent background.

Sprites you need to draw:

Player ship, facing up, roughly 32×24px
3 alien types · 2 walk frames each, squid, crab, ufo-row
Explosion, 3-4 frames of pixel burst
Barrier, 5 damage states (full → destroyed)
Player bullet, thin vertical sprite
Enemy bullet, 2 frames for zigzag animation

Keep a consistent colour palette, 4 to 6 colours maximum. Classic Space Invaders uses white aliens on a black background. Simple is fine for a first game.

All PNG sprites saved into res://assets/ · Assigned to correct scenes

Why should you limit your sprite colour palette to 4-6 colours?

Chapter 9 · Main Scene

The Main Scene

The Main scene brings everything together, it creates the player, alien grid, and barriers, and connects all the signals.

Scene ? New Scene ? Node2D root ? rename "Main"
Add AlienGrid as a child node (attach AlienGrid.gd to it)
Add Player (instance Player.tscn) ? position at bottom centre
Add 4 Barrier instances ? spread evenly across the screen
Add a CanvasLayer ? add Labels for score, hi-score, and lives HUD

# Main.gd, signal connections in _ready()
func _ready():
    $AlienGrid.all_dead.connect(_on_wave_clear)
    $AlienGrid.reached_bottom.connect(_on_game_over)
    $AlienGrid.enemy_bullet_fired.connect(_on_enemy_shoot)
    $Player.player_shot.connect(_on_player_shoot)

Signals are Godot's way of sending a message from one node to another without them needing to know about each other. When an alien dies, it emits a signal. Main listens and updates the score.

Main.tscn saved · All nodes added · No errors

What do signals do in Godot?

Chapter 10 · Press Play!

Press Play!

This is the moment you've been working toward. Set Main.tscn as the main scene and press F5.

Project ? Project Settings ? Application ? Run ? set Main Scene to Main.tscn
Press F5 to run the game
Move with arrow keys, shoot with Space

If something doesn't work, read the red error message in the Output panel. It tells you exactly which file and line has a problem. That's how you fix it.

Common fixes:

Aliens not moving → Check AlienGrid.gd is attached to the AlienGrid node
Player invisible → Sprite2D has no texture assigned
Can't shoot → Check Player.gd signal is connected in Main._ready()
Score not updating → GameState Autoload not registered in Project Settings

Game launches · Aliens march · Player moves and shoots · Score updates · Game Over shows

Where should you look first when your game has a bug?

⭐ Chapter 11 · Make It Yours

Make It Even Better

Your game works. Now make it yours. Here are challenges to push further.

Add a UFO that flies across the top row occasionally for bonus points
Add sound effects, laser shoot, alien death, player death, wave clear
Make aliens speed up faster as their numbers drop, tweak _step_interval
Add a High Score that saves to disk using FileAccess
Draw custom alien sprites to replace the placeholders
Add a main menu scene with a Play button and instructions
Export to HTML5 and upload to itch.io, share your game!

You built a complete game from scratch using real GDScript. That makes it REAL programming. 🎉

Which Godot class lets you save a high score to disk?

🚀 Try the Platformer Guide Next →

💻 GDScript Highlights

Key Patterns from the Guide

Real code from the actual game. Each pattern appears in the guide with a full explanation before you type it.

AlienGrid.gd Marching Logic

func _march():
    if _drop_next:
        _drop_next = false
        _dir = -_dir
        position.y += 12
        if position.y > 420:
            reached_bottom.emit()
        return
    position.x += _dir * 12

AlienGrid.gd Speed Up on Kill

func _on_alien_killed(pts, pos):
    _alive_count -= 1
    # Speed up as fewer aliens remain
    _step_interval = max(
        0.08,
        0.8 * (_alive_count / float(COLS * ROWS))
    )
    if _alive_count <= 0:
        all_dead.emit()

AlienGrid.gd Random Shooting

func _random_shoot():
    # Find bottom alien in each column
    var shooters = []
    for c in range(COLS):
        for r in range(ROWS-1, -1, -1):
            if is_instance_valid(aliens[r][c]):
                shooters.append(aliens[r][c])
                break

Bullet.gd Enemy Zigzag

var _anim_t: float = 0.0

func _process(delta):
    position.y += speed * direction * delta
    # Enemy bullets zigzag between 2 frames
    if is_enemy:
        _anim_t += delta * 8
        $Sprite2D.frame = int(_anim_t) % 2

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Make It Yours

Use these free browser tools alongside this workshop to create custom sprites, sounds, levels and colour schemes for your game. No installs. Free forever.

🎨

Pixel Studio

Draw sprites & animations

Create custom sound effects

🎨

Colour Palette

Build a game-ready colour scheme