This document provides instructions for creating a basic space shooter game in Adobe Flash CS4 using ActionScript. It describes how to: 1) Create a movie clip for the player's ship and use keyboard controls to move it around the screen. 2) Make the ship shoot projectiles using the "attachMovie" method and limit its movement within the screen boundaries. 3) Develop enemy ships as additional movie clips that spawn and move across the screen. The document outlines 11 steps to develop these core mechanics of a space shooter game.

1. DPP B2 (c)
JOB SHEET
COURSE : DIPLOMA IN DIGITAL MEDIA DESIGN
SESSION : JAN - JUN 2012 SEMESTER : 4
CODE/SUBJECT : DDM 4323 - GAME DESIGN SHEET NO : JS-8
NO OF STUDENTS : 30 WEEK : 8
LECTURER : AZMI BIN MOHAMED
TOPIC : 8.0 SPACE SHOOTER
8.1 Research and create a basics of movie clips and character
movement for space shooter game
SUB-TOPIC :
8.2 Add an interactive elements; lives and score for game
8.3 Add sound effects using ActionScript.
After completing this topic, students should be able to:
LEARNING 1. Develop their own space shooter games with random enemies.
OUTCOME : 2. Create an interactive element; lives and score for their games.
3. Add a sound effects using ActionScript
TOOLS / 1. Computer
EQUIPMENTS / 2. Projector
MATERIALS : 3. Adobe Flash CS4
INSTRUCTION :
1. Research the ActionScript for creates a space shooter game, character movement and
shoot control using keyboard.
2. Follow step-by-step tutorial below to create a space shooter game.
Page | 1

2. DPP B2 (c)
PROCEDURE :
STEP KEY POINT
Movie Clip and Movement
1. Open Adobe Flash and create new
document (ActionScript 2.0)
 Size: 800x600px
 Frame Rate : 24fps
 Background Color: Black
2. Create a Movie Clip by right clicking your
library tab and selecting "New
Symbol...", make sure "Movie Clip" is
selected and choose a name.
3. Flash will create and open the Movie
Clip for editing, so just paste an image or
draw a space ship with Flash's drawing
tools. After drawing your ship, get back
to the main timeline by click on "Scene
1":
At properties panel; put a variable name
as “ship”.
4. Right click the first frame in your timeline this.onEnterFrame = function()
and select "Actions". Type this: {
if (Key.isDown(Key.RIGHT))
{
Ship._x += 10;
} else if (Key.isDown(Key.LEFT))
{
Ship._x -= 10;
} else if (Key.isDown(Key.UP))
{
Ship._y -= 10;
} else if (Key.isDown(Key.DOWN))
{
Ship._y += 10;
}
}
Page | 2

3. DPP B2 (c)
Shooting
5. This is the second part of the tutorial
and we are going to enable the ship to
shoot. Previously we made our ship fly;
now we are going to make it shoot and
set limits to where it can go.
First we need to make our bullets, right
click the library tab, select "New
Symbol" and give it the name "Bullet".
Before clicking OK, click Advanced,
select "Export for Actionscript" and
make sure the identifier is "Bullet".
6. We do this because we need to export
the Bullet Movie Clip during running time
to create many bullets and we will use
the name determined in identifier to call
it later. Draw a small bullet, and position
it like this:
This is called registration point, in the
stage this is the position of the Bullet
Movie Clip.
7. Now open the actions window of the first this.onEnterFrame = function()
frame of the Movie Clip, insert this code: {
this._x += 12;
if (this._x > 800)
{
this.removeMovieClip();
}
}
8. Now go to the main timeline, select the var i = 0;
first frame and open the actions this.onEnterFrame = function()
{
windows. You will see the previous
.
codes that we have written. Add this .
code to the old one so we can fire our .
bullets: else if (Key.isDown(Key.DOWN))
{
Ship._y += 5;
}
if (Key.isDown(Key.SPACE))
Page | 3

4. DPP B2 (c)
{
i++;
_root.attachMovie("Bullet",
"Bullet" + i,
_root.getNextHighestDepth());
_root["Bullet" + i]._x =
Ship._x + 3;
_root["Bullet" + i]._y =
Ship._y;
}
}
9. Before we finish this tutorial, let's put if (Key.isDown(Key.RIGHT))
some limits to where our ship can go, we {
don't want it to get off the screen. Make if (Ship.hitTest(800, Ship._y,
these changes: true))
{
Ship._x -= 5;
}
Ship._x += 5;
} else if (Key.isDown(Key.LEFT))
{
if (Ship.hitTest(0, Ship._y,
true))
{
Ship._x += 5;
}
Ship._x -= 5;
} else if (Key.isDown(Key.UP))
{
if (Ship.hitTest(Ship._x - 40, 0,
true))
{
Ship._y += 5;
}
Ship._y -= 5;
} else if (Key.isDown(Key.DOWN))
{
if (Ship.hitTest(Ship._x - 40,
600, true))
{
Ship._y -= 5;
}
Ship._y += 5;
}
if (Ship.hitTest(800, Ship._y, true))
{
Ship._x -= 5;
}
Page | 4

5. DPP B2 (c)
Enemies
10. This is the third tutorial of a series about
developing a Space Shooter game, in
this tutorial we are going to make enemy
ships.
Create a new Movie Clip and draw your
enemy ship, don't forget to set the
identifier to "Enemy" and select "Export
to Actionscript".
11. Now drag the enemy Movie Clip to the onClipEvent(load)
stage, give it an instance name of {
"Enemy0", right click it and select function reset()
"Actions". Insert this:
{
var timer = 12;
this._y = Math.random() * 300
this._x = 550
mySpeed = Math.ceil(Math.
random() * 6) + 1;
}
reset();
}
// This part of the code creates a function called
reset() when the Movie Clip loads for the first
time. Inside reset() we set this._y to a random
number between 0 and 600, this._x to 800 and
the speed of our enemy to a random number
between 1 and 6.
12. Then, insert this code: onClipEvent(enterFrame)
{
this._x -= mySpeed;
if (this._x < -10)
{
reset();
}
if (timer >= 12)
{
Math.ceil(Math.random() * 2)
timer = 0;
Page | 5

6. DPP B2 (c)
}
if (dir == 1)
{
this._y -= 3;
} else if(dir == 2)
{
this._y += 3;
}
timer++
}
13. Add this code in the main timeline before var nrEnemies = 3;
the rest of the code. for (i = 1; i < nrEnemies; i++)
{
_root.Enemy.duplicateMovieClip
("Enemy" + i,
_root.getNextHighestDepth());
}
Lives and Score
14. This is the forth part of the development
of a Space Shooter game. In this tutorial
we will add lives, scores and game over
to our game.
Let's start with score.Open the main
timeline code and add this variable: var score = 0;
15. Now open the Bullet's code and add this: this.onEnterFrame = function()
{
this._x += 9;
if (this._x > 550)
{
this.removeMovieClip();
}
for (i = 0; i < _root.nrEnemies;
i++)
{
if (this.hitTest
(_root["Enemy" + i]))
{
_root["Enemy" + i].reset();
_root.score += 10;
this.removeMovieClip();
}
}
}
// This is the code we used before to know if a
bullet hits an enemy, so we can put the score
for killing an enemy there.
Page | 6

7. DPP B2 (c)
16. The score is done; we just need to show
the player his score. To do that, select
the Text Tool and draw it on the stage.
Write "Score:"
17. Now draw another Text box on the
stage. Select this new Text box and
change these properties:
18. Now let's make our ship have lives. Add var lives = 3;
another variable in the main code:
19. And make these changes in the code if (this.hitTest(_root["Enemy" + i]))
that checks if the player crashed with an {
_root.lives -= 1;
enemy:
reset()
for(k = 0; k < _root.nrEnemies;
k++)
{
_root["Enemy" + k].reset();
}
}
Page | 7

8. DPP B2 (c)
20. Draw two text boxes again
21. We can see the ship losing lives now,
but nothing happens when it goes lower
than zero. To change that we tell the
player when its game over. Create a new
movie clip.
22. Write "Game Over" using the text tool
and go back to the main timeline.
Page | 8

9. DPP B2 (c)
23. Add this to the Ship's code: if (this.hitTest(_root["Enemy" + i]))
{
_root.lives -= 1;
if (_root.lives <= 0)
{
_root.attachMovie("GameOver",
"GameOver", 100)
_root.GameOver._x = 275
_root.GameOver._y = 150
this.swapDepths(10);
this.removeMovieClip();
}
reset()
for(k = 0; k < _root.nrEnemies;
k++)
{
_root["Enemy" + k].reset();
}
}
Timer
24. Before we start with sound we need to
make some changes. You may have
noticed that our ship shoots bullets as
much as the player press the space bar,
that's not right as it makes the game
much easier.
To prevent that, we are going to add a
timer and the ship will shoot as much as
we want.
First add a new variable: var timer = 8;
Then, make this changes: this.onEnterFrame = function()
{
timer++;
.
. .
if (Key.isDown(Key.SPACE))
{
i++;
if(timer >= 8)
{
_root.attachMovie("Bullet",
"Bullet" + i,
_root.getNextHighestDepth());
_root["Bullet" + i]._x =
Ship._x + 3;
_root["Bullet" + i]._y = Ship._y;
timer = 0;
}
}
}
Page | 9

10. DPP B2 (c)
The code runs like this: Before:
 If timer >= 8 then shoot a bullet and set
timer to 0
 Now that timer = 0, the bullet wont shoot,
so the player has to wait all the code to
run at least 8 timer to shoot again
(timer++ will increase timer by 1 every
frame)
 Timer will be bigger than 8 again and the
player can shoot.
After:
Sound
25. We can add the sound now. You need to
have an mp3 file that's going to be the
sound played when you fire. Now that
you have your sound, click File > Import
> Import to library...Select your mp3 file
and click open, a new file should appear
on the library. Right click it and click
"Linkage..." Check "Export to
ActionScript..." and set the Identifier to
"shoot". This is the same thing we did
previously with the Bullet Movie Clip, we
need the linkage to call this on the code.
Page | 10

11. DPP B2 (c)
26. Add this to the shooting code: if (Key.isDown(Key.SPACE))
{
i++;
if(timer >= 8)
{
_root.attachMovie("Bullet",
"Bullet" + i,
_root.getNextHighestDepth());
_root["Bullet" + i]._x = Ship._x
+ 3;
_root["Bullet" + i]._y = Ship._y;
var shoot_sound = new Sound();
shoot_sound.attachSound("shoot");
shoot_sound.start();
timer = 0;
}
}
27. The game is done! Hope you enjoying
developing and playing it.
REFERENCES : 1. Andrew Rollings, Ernest Adams (2003). Andrew Rollings and
Ernest Adams on Game Design. USA: New Riders
Publishing.
2. Andrew Rollings, Dave Morris (2004). Game Architecture and
Design:A New Edition. USA: New Riders Publishing.
3. Patrick O’luanaigh (2006). Game Design Complete. USA:
Paraglyph Press.
Page | 11