So You Want to Create Your Own Computer Games 8

Designing GameswithGame Maker

Version 6.0
Written by Mark Overmars

Table of Contents

So you want to create your own computer games 8

Installation 10

Registration 12

The global idea 14

Let us look at an example 16

The global user interface 18

File menu 18

Edit menu 19

Add menu 20

Run menu 20

Window menu 20

Help menu 20

The resource explorer 21

Defining sprites 22

Sounds and music 24

Backgrounds 25

Defining objects 26

Events 28

Actions 34

Move actions 34

Main actions, set 1 37

Main actions, set 2 40

Control actions 42

Score actions 45

Drawing actions 47

Using expressions and variables 50

Creating rooms 52

Adding instances 53

Room setting 54

Setting the background 55

Distributing your game 57

Advanced mode 58

File menu 58

Preferences 59

Edit menu 60

Add menu 60

Scripts menu 61

More about sprites 62

Editing your sprites 62

Strips 66

Editing individual sub-images 68

Advanced sprite settings 69

More about sounds and music 71

More about backgrounds 73

More about objects 75

Depth 75

Persistent objects 75

Parents 75

Masks 76

Information 77

More actions 78

More move actions 78

More main actions 79

More control actions 80

More draw actions 81

Particle actions 81

Extra actions 84

More about rooms 86

Advanced settings 87

Adding tiles 87

Views 90

Fonts 92

Paths 94

Defining paths 94

Assigning paths to objects 95

The path event 97

Time Lines 98

Scripts 100

Game information 104

Global Game Settings 105

Graphics options 105

Resolution 106

Various other options 107

Loading options 108

Constants 109

Including Files in Stand-alone Games 109

Error options 111

Information about the game 111

Speed considerations 112

GML Language overview 113

A program 113

Variables 113

Assignments 114

Expressions 114

Extra variables 115

Addressing variables in other instances 116

Arrays 118

If statement 119

Repeat statement 120

While statement 120

Do statement 121

For statement 122

Switch statement 122

Break statement 123

Continue statement 123

Exit statement 124

Functions 124

Scripts 124

With constructions 125

Comment 127

Functions and variables in GML 127

Computing things 129

Constants 129

Real-valued functions 129

String handling functions 130

Dealing with dates and time 131

Game play 135

Moving around 135

Paths 138

Motion planning 139

Collision checking 143

Instances 144

Deactivating instances 146

Timing 148

Rooms 149

Score 151

Generating events 151

Miscellaneous variables and functions 154

User interaction 157

The keyboard 157

The mouse 160

The joystick 161

Game graphics 162

Sprites and images 162

Backgrounds 164

Drawing sprites and backgrounds 165

Drawing shapes 167

Fonts and text 170

Advanced drawing functions 172

Tiles 177

The display 179

The window 180

Views 184

Transitions 186

Repainting the screen 187

Sound and music 189

Basic sound functions 189

Sound effects 191

3D sound 194

CD music 195

Splash screens, highscores, and other pop-ups 197

Splash screens 197

Pop-up messages and questions 198

Highscore list 200

Resources 202

Sprites 202

Sounds 203

Backgrounds 203

Fonts 204

Paths 204

Scripts 205

Time lines 205

Objects 205

Rooms 206

Changing resources 207

Sprites 207

Sounds 209

Backgrounds 209

Fonts 211

Paths 212

Scripts 213

Time lines 213

Objects 213

Rooms 215

Files, registry, and executing programs 218

Files 218

Registry 221

INI files 222

Executing programs 224

Data structures 225

Stacks 225

Queues 226

Lists 227

Maps 228

Priority queues 229

Creating particles 231

Particle types 231

Particle systems 235

Emitters 236

Attractors 238

Destroyers 239

Deflectors 240

Changers 241

Firework Example 242

Multiplayer games 244

Setting up a connection 244

Creating and joining sessions 245

Players 247

Shared data 247

Messages 248

Using DLL's 250

3D Graphics 254

Going to 3D mode 255

Easy drawing 256

Drawing polygons in 3D 256

Drawing basic shapes 258

Viewing the world 260

Transformations 262

Fog 265

Lighting 265

Final words 266

So you want to create your own computer games

Playing computer games is fun. But it is actually more fun to design your own computer games and let other people play them. Unfortunately, creating computer games is not easy. Commercial computer games you buy nowadays typically take one to three years of development with teams of anywhere between 10 and 50 people. Budgets easily reach millions of dollars. And all these people are highly experienced: programmers, art designers, sound technicians, etc.

So does this mean that it is impossible to create your own computer games? Fortunately no. Of course you should not expect to create your own Quake or Age of Empires within a few weeks. But that is also not necessary. Simpler games, like Tetris, Pacman, Space Invaders, etc. are also fun to play and a lot easier to create. Unfortunately they still require good programming skills to handle the graphics, sounds, user interaction, etc.

But here comes Game Maker which was written to make it a lot easier to create such games. There is no need to program. An intuitive and easy to use drag-and-drop interface allows you to create your own games very quickly. You can import and create images, sprites (animated images) and sounds and use them. You can easily define the objects in your game and indicate their behavior, and you can define appealing rooms with scrolling backgrounds in which the game takes place. And if you want full control there is actually an easy-to-use programming language built into Game Maker that gives you full control over what is happening in your game.

Game Maker focuses on two-dimensional games. So it is not meant to create 3D worlds like Quake, even though there is some limited functionality for 3D graphics. But don’t let this put you down. Many great games, like Age of Empires, the Command & Conquer series, and Diablo use two-dimensional sprite technology, even though they look very 3-dimensional. And designing two-dimensional games is a lot easier and faster.

Game Maker has both a free and a registered version. The free version can obviously be used free of charge. And you can freely distribute the games you create with it, you can even sell them if you like. See the enclosed license agreement for more details. You are strongly encouraged to register your copy of Game Maker. It will unlock a number of additional features in Game Maker and it will remove the logo when running games. This will also support the further development of Game Maker.

This document will tell you all you need to know about Game Maker and how you can create your own games with it. Please realize that, even with a program like Game Maker, designing computer games is not completely effortless. There are too many aspects that are important: game play, graphics, sounds, user interaction, etc. Start with easy examples and you will realize that creating games is great fun. Also check the web site

http://www.gamemaker.nl/

for lots of examples, tutorials, ideas, and links to other site and forums. And soon you will become a master game maker yourself. Enjoy.

Installation

You probably already did this but if not, here is how to install Game Maker. Simply run the program gmaker.exe. Follow the on-screen instructions. You can install the program anywhere you like but it is best to follow the default suggestions given. Once installation is completed, in the Start menu you will find a new program group where you can start Game Maker and read the help file.

The first time you run Game Maker you are asked whether you want to run the program in Simple or Advanced mode. If you have not used a game creation program before and you are not an experienced programmer, you had better use simple mode (so select No). In simple mode fewer options are shown. You can easily switch to advanced mode later using the appropriate item in the File menu.

Within the installation folder (default C:\Program Files\Game_Maker6\) there will be a number of other folders:

·  examples contains a number of example games for you to check and/or change.

·  lib contains a number of libraries of actions. If you want to install additional action libraries you must put them in this folder.

·  sprites this folder is meant to contain sprites you can use. The default installation does install just a few sprites, but from the Game Maker website (http://www.gamemaker.nl/) you can load a number of resource packs that contain additional sprites, sounds, backgrounds, etc.

·  backgrounds, sounds similar folders that are meant to contain the background images and sounds.

Requirements

Game Maker requires a modern Pentium PC running Windows 98SE, 2000, Me, XP, or later. A graphics card with at least 16MB of memory is required for most created games. (For simple games an 8MB graphics card is sufficient.) It requires a screen resolution of at least 800x600 and 65000 (16-bit) colors. It requires DirectX version 8.0 or later to be installed on your computer. (You can download the newest version of DirectX from the Microsoft website at: http://www.microsoft.com/windows/directx/.) When designing and testing games, the memory requirements are pretty high (at least 64 MB and preferably more). When just running games, the memory requirements are a lot less severe and depend a lot on the type of game.

Registration

Game Maker can be used free of charge. The unregistered version, though, has some limitations and shows a little logo when running a game. To unlock the additional features, remove the logo, and support the further development of the software, you are strongly recommended to register your copy of Game Maker. Registration will add the following features:

·  No Game Maker logo when running a game.

·  Rotated, color blended and translucent sprites.

·  Additional actions for e.g. CD music, rotated text, and colorized shapes.

·  Special sound effects and positional sound.

·  A number of advanced drawing functions, e.g. textured polygons.

·  A particle system to create fireworks, flames, rain, and other effects.

·  Functions for 3D graphics.

·  The possibility of making multiplayer games that can be played over a network.

·  Functions to create and modify resources (sprites, backgrounds, etc.) while the game is running.

·  A collection of functions to create and use data structures.

·  Functions for motion planning.

·  The possibility of extending Game Maker using DLLs.

The registration fee for Game Maker is only 15 Euro or an equivalent amount in another currency, currently e.g. US $ 18. There are a number of ways in which you can register your copy of the program. The easiest way is to use online registration using a secure credit card payment system or a PayPal account. Alternatively you can transfer money to our bank account, send us a money order or send cash. Details can be found on the Game Maker registration web site:

http://www.gamemaker.nl/registration.html

To register your copy of Game Maker use the web site above or choose Registration from the Help menu. At the left of the form that appears click the button Go to Registration Webpage. You will be directed to our web page where the different registration options are indicated, including the online registration.

Once your registration has been received an email will be sent to you with the name and key and information on how to enter the key in the program. To enter the key, again choose Registration from the Help menu. At the left of the form press the button Enter a Registration Key. Type the name and the key and press OK. If you made no mistakes the program is registered.

If you had a registered version of version 5 of Game Maker installed on your machine you can exchange your version 5 registration key for a version 6 registration key. To this end choose Registration from the Help menu. At the left of the form a button Convert a Version 5 Key should be visible in this case. (If not there is no valid version 5 registration or your version 6 is already registered.) Also a text is shown explaining how to convert keys. Carefully read and follow the instructions and then press the button.

The global idea

Before delving into the possibilities of Game Maker it is good to get a feeling for the global idea behind the program. Games created with Game Maker take place in one or more rooms. (Rooms are flat, not 3D, but they can contain 3D-looking graphics.) In these rooms you place objects, which you can define in the program. Typical objects are the walls, moving balls, the main character, monsters, etc. Some objects, like walls, just sit there and don’t do anything. Other objects, like the main character, will move around and react to input from the player (keyboard, mouse, and joystick) and to each other. For example, when the main character meets a monster he might die. Objects are the most important ingredients of games made with Game Maker, so let us talk a bit more about them.

First of all, most objects need some image to make them visible on the screen. Such images are called sprites. A sprite is often not a single image but a set of images that are shown one after the other to create an animation. In this way it looks like the character walks, a ball rotates, a spaceship explodes, etc. During the game, the sprite for a particular object can change. (So the character can look different when it walks to the left or to the right.) You can create you own sprites in Game Maker or load them from files (e.g. animated GIF’s).

Certain things will happen to objects. Such happenings are called events. Objects can take certain actions when events happen. There are a large number of different events that can take place and a large number of different actions that you can let your objects take. For example, there is a creation event when the object gets created. (To be more precise, when an instance of an object gets created; there can be multiple instances of the same object.) For example, when a ball object gets created you can give it some motion action so that it starts moving. When two objects meet, you get a collision event. In such a case you can make the ball stop or reverse direction. You can also play a sound effect. To this end Game Maker lets you define sounds. When the player presses a key on the keyboard there is a keyboard event, and the object can take an appropriate action, like moving in the direction indicated. We hope you get the idea. For each object you design, you can indicate actions for various events; in this way defining the behavior of the object.