BOOKS FOR PROFESSIONALS BY PROFESSIONALS® Manderscheid Beginning HTML5 Games RELATED with CreateJS Beginning HTML5 Games with CreateJS provides a hands-on approach to get you up and running with the most comprehensive tools available for HTML5 Canvas game development. Whether you are brand new to making games or an experienced game developer, you’ll learn to fully utilize the CreateJS suite to bring your new or existing game techniques to desktop and mobile devices. This book covers everything from creating graphics in HTML5 Canvas to capturing user input (whether from keyboard, mouse, or touch) to using a state machine for efficient game control. There are practical (and fun) examples throughout the book, with four full game projects, including a mobile RPG. The book also covers optimizing your games for mobile and publishing them to app stores. HTML5 games are growing more and more popular, and the demand for HTML5 Canvas skills is on the rise. The CreateJS suite is a powerful toolset that will help you manage Canvas drawing and animations, asset loading, sound management, complex tweening, and much more. Using these robust libraries, you can build powerful and engaging games that reach a wide range of audiences and devices. What You’ll Learn: • HTML5 Canvas drawing and animations using EaselJS and TweenJS • Loading and managing assets using PreloadJS • Sound management using SoundJS • Core game development techniques such as state machines and object pooling • Extending EaselJS DisplayObjects using object-oriented JavaScript • JavaScript debugging • Wrapping HTML5 games and publishing them to app store Shelve in ISBN 978-1-4302-6340-1 Web Development/JavaScript 54499 User level: Beginning–Intermediate SOURCE CODE ONLINE 9781430263401 www.apress.com For your convenience Apress has placed some of the front matter material after the index. Please use the Bookmarks and Contents at a Glance links to access them. Contents at a Glance About the Author ��������������������������������������������������������������������������������������������������������������xvii About the Technical Reviewer �������������������������������������������������������������������������������������������xix Acknowledgments �������������������������������������������������������������������������������������������������������������xxi Introduction ���������������������������������������������������������������������������������������������������������������������xxiii ■ Chapter 1: Getting to Know CreateJS ��������������������������������������������������������������������������������1 ■ Chapter 2: Making and Animating Graphics ��������������������������������������������������������������������15 ■ Chapter 3: Capturing User Input ��������������������������������������������������������������������������������������31 ■ Chapter 4: Game Project: Progressive Break-it ���������������������������������������������������������������55 ■ Chapter 5: Using and Managing Bitmap Images �������������������������������������������������������������77 ■ Chapter 6: Sprites and Sprite Sheet Animations �����������������������������������������������������������109 ■ Chapter 7: Game Project: Fakezee ���������������������������������������������������������������������������������137 ■ Chapter 8: Extending EaselJS Display Objects ��������������������������������������������������������������177 ■ Chapter 9: Sounds and Asset Management �������������������������������������������������������������������203 ■ Chapter 10: The State Machine and Scenes ������������������������������������������������������������������221 ■ Chapter 11: Game Project: Space Hero �������������������������������������������������������������������������239 ■ Chapter 12: Building for Mobile Browsers ��������������������������������������������������������������������279 ■ Chapter 13: Packaging and Compiling with PhoneGap Build ����������������������������������������291 ■ Chapter 14: Game Project: The Villager RPG �����������������������������������������������������������������305 Index ���������������������������������������������������������������������������������������������������������������������������������381 v Introduction CreateJS is not a game engine. It was written to create rich, interactive experiences of all kinds by providing tools for HTML5 applications. EaselJS, the library in the suite upon which all games in this book are based, helps manage and control graphics in HTML5 Canvas. Because the very nature of Canvas lends itself nicely to both performance and the technical procedures of classic game development, EaselJS very much feels like it’s meant for games in many ways. Although this is not entirely true, EaselJS, along with the other tools in the CreateJS suite, are a perfect combination of tools to do just that. The low level, heavy lifting of drawing and management of your game graphics are taken care of, which gives you more freedom to concentrate on the game logic itself. Tools for preloading assets, playing and managing audio, and creating complicated tweens are also included in CreateJS, and can also be used extensively to build engaging games. A large advantage of using CreateJS for games, as opposed to the other game-specific HTML5 libraries out there, is the freedom to create and fine-tune your own game framework. In many popular markets, primarily casual, board, and turn-based games, the overhead of a framework built for tiling, heavy collision, and physics is not necessary. Simply utilizing a tool to draw and sort graphics on the canvas is all that is needed. That’s where this book comes in. It puts you right in the middle between complicated native canvas management and being tied down to a specific framework to build your games. This is not to say these other frameworks are bad. In fact they are quite good, especially Phaser and ImpactJS. Depending on the type of game you are building, they can often be the better choice. The purpose of this book is to not only teach you to write these game development techniques yourself, but to give you the skills to mold your own workflow and frameworks using the CreateJS tools. What’s more, the skills learned in this book will fully prepare you to create endless, rich HTML5 applications that extend far beyond games. The book itself is split up into two parts. The first half of the book concentrates on learning the APIs of the suite. Game development techniques will be introduced, focusing on how they can be used with EaselJS and TweenJS. The second half of the book will take your new CreateJS skills to the next level by learning more advanced, objected-oriented JavaScript, asset loading and management, and code organization. More advanced game development techniques will also be learned, which will result in performance gains; mobile optimization will be introduced as well. You’ll find that the libraries in CreateJS are powerful and extremely easy to use. You’ll also learn the best tools and applications used to create the graphical assets needed for your games, and how to best use them in conjunction with EaselJS. There are several small exercises, including four full game project chapters. I hope you find this book both fun and educational, and that it will encourage you to create new and exciting applications using CreateJS. For support, updates on code APIS, and general discussion on this book, please visit the public forum at https://plus.google.com/u/0/communities/109922548905806388011. xxiii Chapter 1 Getting to Know CreateJS Before you can start building your games, you need to get familiar with the CreateJS suite. I’ll take a look at each library in the suite and give a brief overview on how to use them. A few JavaScript techniques will also be examined in effort to learn best practices when working with CreateJS, and the final code example will show the harmony that can easily be achieved with the entire suite at work. Getting Started The best place to get started is to head over to the official web site, http://createjs.com, shown in Figure 1-1. Figure 1-1. The CreateJS official web site 1 Chapter 1 ■ GettinG to Know CreateJS Here you can gain access to the latest builds of the suite, as well as view official tutorials and a showcase of recent projects using the suite. Be sure to view this showcase to get an idea of the cool things you can do with CreateJS. You’ll also notice the highly-detailed documentation that is available for each library in the suite. Along with being one of the largest JavaScript libraries out there today, CreateJS has amazing documentation to go with it. As you progress in your learning of the suite, these documents will prove to be priceless in extending your skills and optimizing your code. To acquire the necessary libraries, click the download button on the home page of the site. You’ll be taken to https://github.com/CreateJS/ where you can download all of the latest builds. For this book you’ll need all four libraries in the toolset. At the time of writing this book, the following versions were used: • TweenJS version 0.5 • PreloadJS version 0.4 • EaselJS version 0.7 • SoundJS version 0.5 These four libraries are everything you need to draw and animate graphics, play sound effects and music, and preload your game assets. You’ll be using one or more of these libraries throughout the code examples that you’ll build in this book. Place them in an area where you can easily include them in your documents while following along with the exercises. I suggest creating a project directory and placing these libraries in a folder named lib so that you can easily set up your files for each exercise to match the code listings. Let’s start by taking a look at the most important tool in the suite when building HTML5 games. EaselJS EaselJS is by far the most frequently used tool in the suite when building games. It’s where all graphics and interactivity are managed and drawn to an HTML5 Canvas element. The API is based on a hierarchal display list that should be very familiar to anyone that has worked with Flash and ActionScript 3.0. Along with a core interaction model and various helper classes, EaselJS makes working with canvas a lot more manageable than going it alone. Since EaselJS relies entirely on HTML5 Canvas, it’s important to understand what it is and how it works. If you are already familiar with techniques such as blitting and/or working with Flash Stage3D, you already have a pretty good idea of how it works. If not, then you might find the concept a bit complicated at first, but rest assured that EaselJS will smooth out those learning curves almost instantly. In any case, let’s start this section by diving into the basics of what Canvas is and how to work with it natively. HTML5 Canvas Canvas is an HTML5 element that creates a rectangle in your document used for drawing graphics on the fly with JavaScript. It contains very few attributes or applicable styles. It’s quite literally an empty canvas. Although this programmatically driven graphics environment makes it a powerful tool with many opportunities for rich interactive creation, it’s a low-level system that requires a lot of manual drawing management. You are responsible for both drawing and erasing all pixels, and no graphics on the canvas are directly tied to any properties or objects. The best analogy I’ve come up with to describe this concept is as follows. Imagine you have a magnet board hanging on the wall, and to the right of it is a dry erase board. The magnet board consists of three butterfly magnets laid out horizontally. The dry erase board has the same three butterflies but are drawn on the board with a marker. If I were to tell you to change the position of the second butterfly on the magnet board by moving it down two inches, you wouldn’t need much thought on how to accomplish this. You would simply grab the butterfly with your finger and pull it down two inches. You simply changed its position. In a typical scripting language it may look something like this: butterfly.y += 200; 2 Chapter 1 ■ GettinG to Know CreateJS Now imagine I told you to do the same thing on the dry erase board. You might pause for a minute but you’d ultimately come to only one solution. You would need to erase it, and then draw it again at its new desired position. This is precisely how Canvas works. It’s not enough to manage and update the next position of every sprite in your game; you need to manually erase and redraw them as well. These visual graphics are not collectively retainable, but are simply pixels painted on to the canvas with no other reference to what they are or represent. To demonstrate how this looks in action, let’s look at a simple example of how you would do this in JavaScript using the Canvas API (see Listing 1-1). The result is demonstrated in Figure 1-2. Listing 1-1. Drawing and Moving Graphics with the Canvas API var canvas = document.getElementById("canvas"); var ctx = canvas.getContext("2d"); var butterfly = new Image(); butterfly.src = "images/butterfly.png"; butterfly.onload = drawButterflies; function drawButterflies() { ctx.drawImage(butterfly, 0, 0, 200, 138, 0, 0, 200, 138); ctx.drawImage(butterfly, 0, 0, 200, 138, 200, 0, 200, 138); ctx.drawImage(butterfly, 0, 0, 200, 138, 400, 0, 200, 138); setTimeout(moveButterfly,1000); } function moveButterfly(){ ctx.clearRect(0,0, canvas.width,canvas.height); ctx.drawImage(butterfly, 0, 0, 200, 138, 0, 0, 200, 138); ctx.drawImage(butterfly, 0, 0, 200, 138, 200, 200, 200, 138); ctx.drawImage(butterfly, 0, 0, 200, 138, 400, 0, 200, 138); } Figure 1-2. Bitmaps drawn onto the canvas using the Canvas API 3 Chapter 1 ■ GettinG to Know CreateJS At first glance, the initial drawing of the graphics doesn’t seem too complicated. You draw your graphic by passing in a reference to the loaded image plus some coordinates and dimensions that dictate what you grab from the loaded bitmap and where to draw it on the canvas. Now take a look at the function that moves your second butterfly. You are responsible for not only redrawing your graphics again with newly calculated positions, but clearing all of your previous graphics as well. If you didn’t first clear the canvas before redrawing your butterfly in its new position, you’d end up with four butterflies (see Figure 1-3). Figure 1-3. Results when not first clearing your canvas before drawing new positions In this example, you are simply hardcoding the new position of the second butterfly, but as you add more and more sprites to your games, the management of what gets drawn, when you draw, and where you draw it becomes increasingly difficult to maintain. EaselJS with HTML5 Canvas Elegant canvas management is where EaselJS comes in. It handles the heavy lifting of managing and drawing graphics so you can concentrate on your game logic, thus making your games as fun and enjoyable as possible. You can rest assured that your sprite objects will be properly drawn and moved appropriately so you can focus on the shelf life and behavior of these game assets while remaining completely decoupled from the rendering process. Let’s take a quick look at what this code might look like if you were doing the exact same thing using EaselJS (see Listing 1-2). 4 Chapter 1 ■ GettinG to Know CreateJS Listing 1-2. Drawing and Moving Graphics with EaselJS function drawButterflies() { var imgPath = 'images/butterfly.png'; butterfly1 = new createjs.Bitmap(imgPath); butterfly2 = new createjs.Bitmap(imgPath); butterfly3 = new createjs.Bitmap(imgPath); butterfly2.x = 200; butterfly3.x = 400; stage.addChild(butterfly1,butterfly2,butterfly3); stage.update(); setTimeout(moveButterfly, 1000); } function moveButterfly(){ butterfly2.y += 200; stage.update(); } As you can see, the EaselJS API makes your code much more clean and manageable. You can refer to and transform what you see on screen as if they were retainable objects, and not get bogged down with the details of what actually connects your graphics with the logical display objects that are created to represent them. Again, the things you see on the canvas are never the same as an object that holds its properties, but merely a graphical representation of it. But you don’t need to worry about this because EaselJS will manage that for you. If you tell the butterfly to move, it will move. Much nicer! You’ll also notice that you are adding graphics to and updating an object named stage. This is a reference to Stage, the root display object in which all graphics are drawn to with EaselJS. I will be covering this in depth before starting the actual exercises, which will begin in the next chapter. Let’s take one more look at the power of EaselJS before moving on with the rest of the suite. As you can imagine, layers will be playing a large role in your graphics management when it comes to game development. With Canvas, any pixel drawn in the same coordinates of another will completely erase and replace it. By now that should seem clear so its no surprise that controlling graphics that overlay each other can quickly become difficult to manage. Luckily, EaselJS consists of the concept referred to as the display list. With it you are able to easily add and remove graphics, manipulate the order in which they are drawn, access them by their index in the list, and a whole lot more. I will be covering the display list in more detail later in this section. Using the previous dry erase board analogy, let’s consider one more scenario. This time, each board consists of two butterflies, each with one butterfly slightly overlapping another. Imagine swapping the depths of the butterflies on the magnet board. Once again you’re able to quickly accomplish this, this time by simply grabbing both butterflies and replacing one’s layer with the other. Using DOM and jQuery, you might do something like this: $('#butterfly1').css('z-index',1); $('#butterfly2').css('z-index',2); Simple enough; just move your butterflies. But with the dry erase board you’d have no other choice but to erase both butterflies and redraw them. Again, this is exactly how you would do it with Canvas. You’d draw your two butterflies slightly overlapping using the drawing techniques in the previous Canvas API example. Then, when it comes time to swap their layers, you’d have to erase the current graphics and redraw your butterflies. Only this time you’d change the order in which you drew them (see Figure 1-4). This provides the illusion of depth swapping. To manage those depths, and the depths of every graphic in your game, you’d need to come up with a system to factor the order in which your graphics are drawn and execute the code accordingly when drawing. 5 Chapter 1 ■ GettinG to Know CreateJS Figure 1-4. Image depth swapping on Canvas It’s no surprise that this can be handled in a much simpler way using the EaselJS API. Since all of your drawing is taken care of, including the depths of those drawings, this is accomplished with one simple line of code. stage.swapChildren(butterfly1,butterfly2); This is a fine example of the power we have in graphic management and it’s all due to the concept of a display list, which EaselJS is built upon. Anything in a display list is referred to as a child, and the collective items in that stack are referred to as children. In the examples so far, your butterflies are children of the stage object. There are several handy methods that let you quickly access, manipulate, and remove these “stacked” children on your stage. The following are a few of these key methods and they will be used in depth throughout the examples and games in this book: • addChild • removeChild • removeAllChildren • getChildAt • setChildIndex These are just to name a few but are probably the most used when it comes to game development. A full list of methods used to control the display list can be found at www.createjs.com/Docs/EaselJS/classes/Container.html. Because of this display list and the API to control it, you can completely ignore the tedious tasks of drawing management and concentrate on what, when, and why your graphics should appear or go away. It’s the one key concept that makes EaselJS such a powerful and easy-to-use library for drawing to the canvas. You’ll see much more EaselJS magic as you progress in the book and start making your games, but let’s look at the rest of the suite. We’ll move on to animation. TweenJS TweenJS is a powerful, lightweight tweening engine that helps you easily animate your display objects in Easel.JS. In fact, you can use TweenJS to tween just about anything, including DOM elements and even sounds. Since you are only concerned about EaselJS and how to use it for games, I will only be covering its use with your easel graphics. 6