Hypertext Markup Language, HTML, has been shaping the Internet in the last few decades. It defines how content is structured in the Web and the linkage between related pages. HTML has kept evolving from version 2 to HTML 4, and later to XHTML 1.1. Thanks to the web applications and social networking applications, it the era of HTML5 now.
Cascading Style Sheet (CSS) defines how web pages are presented visually. It styles all HTML elements and the styles of their states, such as hover and active.
JavaScript is the logic controller of a web page. It makes the web page dynamic and provides client-side interaction between the page and users. It accesses the HTML through Document Object Model (DOM). It controls the new HTML features via their APIs.
There are modern web browsers in most desktop and mobile devices. These latest web techniques bring us the new game market—the HTML5 games. With the new power from these techniques, we can design games with HTML5 elements, CSS3 properties, and JavaScript to play in most browsers and mobile devices.
In this chapter, we will cover the following topics:
Discovering new features in HTML5
Discussing what makes us so excited around HTML5 and CSS3
Previewing what games we are going to build in later chapters
Preparing the development environment
So, let's get started.
There are many new things introduced in HTML5 and CSS3. Before getting our hands dirty by creating the games, let's take an overview of the new features and see how we can use them to create games.
Canvas is an HTML5 element that provides drawing shapes and bitmap manipulation functions in low levels. We can imagine the Canvas element as a dynamic image tag. The traditional <img> tag shows a static image. This image is usually static after it's loaded. We can change the <img> tag to another image source or apply styles to the image, but we cannot modify the image's bitmap context itself.
On the other hand, Canvas is like a client-side dynamic <img> tag. We can load images inside it, draw shapes there, and interact with it using JavaScript.
Canvas plays an important role in HTML5 game development. It is one of our main focus areas in this book.
Background music and sound effects are essential elements in game design. HTML5 comes with native audio support from the audio tag. Thanks to this feature, we do not require the proprietary Flash Player to play sound effects in our HTML5 games. However, there have been some restrictions on using Web Audio on the Web. We will discuss the usage of the audio tag in Chapter 6, Adding Sound Effects to Your Games.
Besides the traditional keyboard and mouse events, there are touch events that we can use to handle single and multi-touch events. We can design a game that works on mobile devices with touches. We can also handle gestures by observing the touch patterns.
GeoLocation lets the web page retrieve the latitude and longitude of the user's computer. For example, Google's Ingress game makes use of GeoLocation to let players play the game in their real city. This feature may not have been so useful years ago when everyone was using the Internet with their desktop. There are not many things for which we need the accurate location of the road of the user. We can get the rough location by analyzing the IP address.
These days, more and more users are going on the Internet with their powerful smartphones. Webkit and other modern mobile browsers are in everyone's pocket. GeoLocation lets us design mobile applications and games to play with the inputs of a location.
WebGL extends the Canvas element by providing a set of 3D graphics APIs in the web browser. The APIs follow the standard of OpenGL ES 2.0. WebGL provides a powerful GPG-accelerated, 3D rendering API for HTML5 games. Some 3D game engines support the export of WebGL, including the popular Unity engine. We can expect to see more HTML5 3D games waiting to be released using WebGL.
The techniques used to create games with WebGL are quite different than using Canvas. Creating games in WebGL requires handing the 3D models and using an API similar to OpenGL. Therefore, we will not discuss WebGL game development in this book.
WebGL has a better performance than 2D Canvas because of the GPU-rendering support. Some libraries allow a game to use Canvas 2D drawing API, and the tools render the canvas by drawing on WebGL to gain performance. Pixi.js (http://www.pixijs.com), EaselJS (http://blog.createjs.com/webgl-support-easeljs/) and WebGL-2D (https://github.com/corbanbrook/webgl-2d) are several such tools among them.
WebSocket is part of the HTML5 spec to connect the web page to a socket server. It provides us with a persistent connection between the browser and server. This means that the client does not need to poll the server for new data within short periods. The server will push updates to the browsers whenever there is any data to update. One benefit of this feature is that game players can interact with each other in almost real time. When one player does something and sends data to the server, we can send the individual player the update to create one-on-one real-time page play, or we can iterate all the connections in the server to send an event to every other connected browser to acknowledge what the player just did. This creates the possibility of building multiplayer HTML5 games.
HTML5 provides a persistent data storage solution to web browsers.
Local Storage stores key-value pair data persistently. The data is still there after the browser terminates. Moreover, the data is not limited to be accessible only to the browsers that created it. It is available to all browser instances with the same domain. Thanks to Local Storage, we can easily save a game's status, such as progress and earned achievements, locally in web browsers.
Another database on web browser is IndexedDB. It's key-value pair too, but it allows storing objects and querying data with condition.
Normally, we need an Internet connection to browse web pages. Sometimes, we can browse cached offline web pages. These cached offline web pages usually expire quickly. With the next offline application introduced by HTML5, we can declare our cache manifest. This is a list of files that will be stored for later access when there is no Internet connection.
With the cache manifest, we can store all the game graphics, game control JavaScript files, CSS stylesheets, and the HTML files locally. We can also pack our HTML5 games as offline games on the desktop or mobile devices. Players can play the games even in the airplane mode. The following screenshot from the Pie Guy game (http://mrgan.com/pieguy) shows an HTML5 game being played on an iPhone without an Internet connection; note the little airplane symbol indicating the offline status:
CSS is the presentation layer and HTML is the content layer. It defines how the HTML looks. We cannot miss CSS when we create games with HTML5, especially DOM-based games. We may purely use JavaScript to create and style the games with a Canvas element. However, we need CSS when we create DOM-based HTML5 games. Therefore, let's take a look at what is new in CSS3 and how we can use the new properties to create games.
Instead of directly drawing and interacting on Canvas' drawing board, new CSS3 properties let us animate the DOM in different ways. This makes it possible to make more complicated DOM-based browser games.
Traditionally, the style changes immediately when we apply a new style to an element. CSS3 transition renders in-between styles during the style changes of the target elements over duration. For example, here, we have a blue box and want to change it to dark blue when we do a mouseover. We can do this by using the following code snippets:
HTML:
<a href="#" class="box"></a>
CSS:
a.box {
display: block;
width: 100px;
height: 100px;
background: blue;
}
a.box:hover {
background: darkblue;
}The box changes to dark blue immediately when we do a mouseover. With CSS3 transition applied, we can tween the styles for a specific duration and easing value:
a.box {
transition: all 0.5s ease-out;
}Tip
Downloading the example code
For all the Packt Publishing books you have purchased, you can download the example code files from your account at http://www.packtpub.com. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.
In the past, we needed JavaScript to calculate and render the in-between styles; this is much slower than using CSS3 transition because the browser natively makes the effects happen.
Note
Since some CSS3 specifications are still in the draft stage and not yet fixed, implementation from different browser vendors may have some minor differences to the W3C spec. Therefore, browser vendors tend to implement their CSS3 properties with a vendor prefix to prevent conflict.
Safari uses the -webkit- prefix. Opera uses the -o- prefix. Firefox uses the -moz- prefix and IE uses the -ms- prefix. Chrome used to use -webkit-, but now it doesn't use any prefix after switching its engine to Blink. It is a little complex now to declare a CSS3 property, such as flex, with several lines of the same rule for several browsers. We can expect the prefix to be dropped after the property spec is fixed.
In order to make the code cleaner in this book, I will use non-vendor prefix for all the properties in this book. I recommend you to use JavaScript-based libraries to automatically add the required vendor prefix for different web browsers. The prefix-free library (http://leaverou.github.io/prefixfree/) is one of them.
Alternatively, if you are using preprocessors, the compilation process may also add the necessary vendor prefix for you.
CSS3 transform lets us scale the elements, rotate them, and translate their position. CSS3 transform is divided into 2D and 3D. By combining the transform origin and 3D rotation and translation, we can animate 2D graphics in a 3D space.
CSS3 transition is one type of animation. It declares the tweening animation between two styles of the elements.
CSS3 animation is one step further in animation. We can define key frames of an animation. Each key frame contains a set of properties that should change at any particular moment. It is like a set of CSS3 transitions that are applied in sequence to the target element.
The AT-AT Walker (http://anthonycalzadilla.com/css3-ATAT/index-bones.html) shows a nice demo on creating a skeleton bone animation with CSS3 animation key frames, transform, and transition. This is shown in the following diagram:
We have explored several new key features from HTML5 and CSS3. With these features, we can create HTML5 games on browsers. But why do we need to do that? What is the benefit of creating HTML5 games?
The web standards are open and free for use. In contrast, third-party tools are usually proprietary and they cost money. With proprietary technologies, the support from them may drop because of changes to the company's focus. The standardization and openness of HTML5 ensures that we will have browsers that support it.
With the built-in support of all the HTML5 features in modern browsers, we do not require the users to preinstall any third-party plugin in order to play any file. These plugins are not standard. They usually require an extra plugin installation that you may not be able to install. For instance, millions of Apple iOS devices around the world do not support third-party plugins, such as Flash Player, in their mobile Safari. Despite whatever the reason might be, Apple does not allow Flash Player to run on their Mobile Safaris, instead, HTML5 and the related web standard are what they get in their browsers. We can reach this user base by creating HTML5 games that are optimized for mobiles.
When we code the game in a Canvas, there are some rendering engines that can translate our Canvas drawing code into OpenGL, thus rendering in native mobile device. This means that while we are still coding the game for a web browser, our game can gain benefits in mobile devices by the native app OpenGL rendering. Ejecta (http://impactjs.com/ejecta) and CocoonJS (http://ludei.com/cocoonjs) are two such engines.
In traditional game designing, we build games within a boundary box. We play video games on a television. We play Flash games in web browsers with a rectangle boundary.
Using creativity, we are not bound in a rectangle game stage any more. We can have fun with all the page elements.
Twitch (http://reas.com/twitch/) is a game from Chrome Experiments. It is a collection of mini games where the player has to carry the ball from the starting point to the end point. The fun part is that each mini game is a small browser window. When the ball reaches the destination point of that mini game, it is transferred into the newly created mini game browser to continue the journey. The following screenshot shows the whole map of Twitch with the individual web browsers:
Thanks to the new features of HTML5 and CSS3, we can now create an entire game in the browser. We can control every element in the DOM. We can animate each document object with CSS3. We have Canvas to dynamically draw things and interact with them. We have an audio element to handle the background music and sound effects. We also have Local Storage to save game data, and WebSocket to create a real-time multiplayer game. Most modern browsers are already supporting these features. It is now time to build HTML5 games.
This is a good opportunity to study how different HTML5 games perform by watching other HTML5 games that are made with different techniques.
Coca-Cola had run a campaign known as Ahh (http://ahh.com) with lots of interactive mini games. The interactions combined several techniques that included canvas and device rotation. Most of them work well in both desktop and mobile devices.
Erik, a web designer from Sweden, created an interesting bookmarklet. This is an asteroid-styled game for any web page. Yes, any web page! It shows an abnormal way to interact with any web page. It creates a plane on the website you are reading from. You can then fly the plane using arrow keys and fire bullets using the space bar. The fun part is that the bullets will destroy the HTML elements on the page. Your goal is to destroy all the things on the web page that you choose. This bookmarklet is another example of breaking the boundary of usual browser games. It tells us that we can think outside the box while designing HTML5 games.
The following screenshot shows the plane destroying the contents on the web page:
The bookmarklet is available for installation at http://kickassapp.com. You can even design the space ship that you control.
The creator of a Canvas-based game engine named Impact, created this X-Type (http://phoboslab.org/xtype/) shooting game for different platforms, including web browsers, iOS, and Wii U. The following screenshot shows the game running smoothly in iPhone.
Cursors.io (http://cursors.io) demonstrates a nicely designed real-time multiplayer game. Every user controls an anonymous mouse cursor and takes a journey through the levels of the game by moving the cursor to the green exit. The fun part of the game is that players must help the others to advance to the level. There are toggles that some cursors click on them to unlock the doors. The anonymous players must take up the role to help the others. Someone will take your role so that you can advance to the next level. The more players that help you, the higher your chance is to succeed in the game. In case only a few players are playing and you can't experience the game, I have recorded my playing screen in 12 x speed (at http://vimeo.com/109414542) to let you have a glimpse of how this multiplayer game works. This has been captured in the following screenshot:
Note
We will discuss building a multiplayer game in Chapter 8, Building a Multiplayer Draw-and-Guess Game with WebSockets.
In the following chapters, we are going to build six games. We are going to first create a DOM-based Ping Pong game that can be played by two players in the same machine. Then, we will create a memory matching game with CSS3 animation. Next, we will use Canvas to create an Untangle puzzle game. Later, we will build a music game with audio elements. Then, we will create a multiplayer draw and guess game with WebSocket. Lastly, we will use the Box2D JavaScript port to create a prototype of a physics car game. The following screenshot shows the memory matching game that we will build in Chapter 3, Building a Card-matching Game in CSS3. You can play the game at http://makzan.net/html5-games/card-matching/.
The environment for developing HTML5 games is similar to designing websites. We need web browsers and a good text editor. Which text editor is good is a never-ending debate. Each text editor comes with its own strengths, so just pick your favorite one. I personally recommend text editors with multiple cursors, for instance, Sublime Text or Brackets. For the browser, we will need modern browsers that support the latest HTML5 and CSS3 specs and provide us with handy tools for debugging.
There are several modern browser choices on the Internet now. They are Apple Safari (http://apple.com/safari/), Google Chrome (http://www.google.com/chrome/), Mozilla Firefox (http://mozilla.com/firefox/), and Opera (http://opera.com). These browsers support most of the features that we will discuss in the examples in the whole book. I personally use Chrome because it has great built-in developer tools. The powerful developer tools make it popular with web and game developers.
We will also need Android phones and an iPad/iPhone to test the games in mobile devices. Simulators may also work, but testing with real devices gives closer results to real-world usage.
In this chapter, we've learned a lot about the basic information of HTML5 games.
Specifically, we covered new features of HTML5 and CSS3. We gave you a glimpse of what techniques we will use to create our games in later chapters—Canvas, audio, CSS animation, and more new features were introduced. We will have many new features to play with. We discussed why we want to create HTML5 games—we want to meet the web standard, meet mobile devices, and break the boundary of a game. We took a look at several existing HTML5 games that were created with different techniques, which we will also use. You can test these games before we create our own. We also previewed the games that we are going to build in the book. At last, we prepared our development environments.
Now that we've some background information on HTML5 games, we're ready to create our first DOM-based, JavaScript-driven game in the next chapter.
