Mastering Android Game Development with Unity: Build high-end Android games with Unity's advanced features

Year by year, Android has increased its maturity level with each new version. Every version introduced new set of features from the user interface to customizations to flexibility to security. In terms of names, these versions are based on names of candy, chocolates, and other sweet stuff, such as Kitkat, Lollipop, and Marshmallow, but that's what makes Android a little more understandable to consumers and developers as well.

The following table highlights the main features of the different Android versions with their API levels as well:

Table 1.1: Era of operating systems from Android Cupcake to Lollipop

The table only shows the changes made by Android operating system's developer, Google Inc. But due to Android's open source nature, other mobile manufacturing companies have also changed and introduced new features and modifications into Android. For example, Samsung has made a custom touch interface called TouchWiz, and HTC has made a custom user interface called HTC Sense. Similarly, Sony has introduced a custom user interface called TimeScape.

Figure 1.1 Latest Android phones launched in year 2014

After the introduction of smart phones, the concept of market store came to existence in software technology, which revolutionized the mobile development industry. A significant role was played by Google Play in that revolution of mobile apps and games. Google Play is the largest market store in smartphones, with more than 2.2 million Android apps, games, books, music, shows, and more. These apps and games have been downloaded more than 50 billion times up to this point, and that marks a huge milestone achieved by Google in just 8 years of Android. You can check out Google Play at http://play.google.com.

Figure 1.2 Google Play on an Android device

Unreal Engine (http://www.unrealengine.com) is a game engine developed by Epic Games. It was an in-house game engine of Epic Games and was first showcased in 1998 first person shooter game Unreal. Unreal Engine is mostly used for creating first-person or third-person shooter games but it has also shown quite good quality in other genres such as stealth, MMORPGs etc. Unreal Engine includes high degree of portability and easy interface features with more logic and behaviors written in C++ language.

The latest release called as Unreal Engine 4 supports almost all platforms supported by Unity including Windows, Xbox One, Windows RT, OS X, Linux, PlayStation 4, iOS, Android, Ouya, and browsers using WebGL.

Unreal Engine 4 was released in March 2014 for the public use. Unreal Engine has nice user interface and navigation controls are very polished and easy to use. Unreal Engine provides very easy flow and interface to create first person shooter games and contains features to produce AAA quality game including real-time global illumination using voxel cone tracing, eliminating pre-computed lighting.

You can download the engine and use it for everything from game development, education, architecture, and visualization to VR, film and animation. When you ship a game or application, you pay a 5% royalty on gross revenue after the first $3,000 per product, per quarter Unreal Engine's learning curve is a little high so it's not best suited for new aspiring game developers:

Figure 1.3 Unreal Engine 4 Interface

Adobe Flash (formerly called as Macromedia Flash) (http://www.adobe.com) is a multimedia and software platform used for creating vector graphics, animations, games, and rich internet applications (RIAs) that can be viewed, played, and executed in Adobe Flash Player. The Flash is widely used for creating animations and mostly advertisements for web browsers but its use of creating games is declined very heavily in recent years by HTML5 framework.

There was a time when Adobe Flash was most popular game engine for online browser games and made a quite big wave of independent game developers creating games for online portals such as Kongregate and Miniclip.

The Adobe Flash includes very easy interface to create amazing and robust animations allowing artists to create vector art directly in the editor. It also supports Adobe Illustrator and Adobe Photoshop layers as well to make it easy integrated with vector art and animations. Adobe Flash allowed developers to port their games and animations from browsers to Desktops (Mac and Windows), Android, and iOS using Adobe AIR framework but couldn't grasp the much attention of game developers and artists due to low performance on end devices.

Adobe Flash has a Free 30-day trial but once the trial is finished you must buy a license unlike other engines discussed in this section.

Figure 1.4 Adobe Flash CC Interface

Game Maker Studio (originally names Animo and later Game Maker) is an event-driven game creation system created by Mark Overmars in Delphi programming language in 1999. Originally created for 2D animations, it quickly moved up high on to being a very robust and easy-to-use drag-drop tool for creating 2D games.

Game Maker Studio uses pre-defined events to create actions in the game, which makes it very easy for developers to create games without needing prior knowledge of programming and coding stuff. The tool comes with a sandboxed language called Game Maker Language (GML), which allows developers to define custom and more complex behaviors for their games.

The Game Maker Studio comes with a clean and slick user interface that lets developers build and deploy their games on Windows, macOS X, Ubuntu, HTML5, Android, iOS, Windows Phone 8, and Tizen. The latest version also introduced Xbox One and PlayStation deployment.

Figure 1.5 Game Maker Studio Interface

Unity (http://unity3d.com) is cross-platform game engine developed by Unity Technologies. It made its first public announcement at Apple's Worldwide Developers Conference in 2005 and supported only game development for Mac OS, but since then it has been extended to target more than 15 platforms for desktop, mobile, and consoles. It is notable for its one-click ability to port games on multiple platforms, including BlackBerry 10, Windows Phone 10, Windows 10, OS X, Linux, Android, iOS, Unity Web Player (including Facebook), Adobe Flash, PlayStation 3, PlayStation 4, PlayStation Vita, Xbox 360, Xbox One, Wii U, and Wii.

Unity has a fantastic interface that lets the developers manage the project really efficiently from the get-go. It has nice drag-drop functionality with connecting behavior scripts written in C# and Boo (a dialect of JavaScript) to define the custom logic and functionality with visual objects quite easily. Unity has been proven quite easy to learn for the new developers who are just starting out with game development and now more large studios have also started it using, and that is also for good reasons.

Unity is one of those engines that provides support for both 2D and 3D games without putting developers in trouble and confusion. It has vast collection of online tutorials, great documentation, and a very helpful community of developers. Also, Unity has the Asset Store, where developers sell reusable components of Unity to reduce the development time and efforts for other developers. You can check Unity Asset Store at http://assetstore.unity3d.com.

Unity Plus and Pro are available for a fee, and Unity Personal has no fee; it is available any use to individuals or companies with less than US $100,000 of annual gross revenue. For more information, visit the Unity store at https://store.unity.com/:

Figure 1.6 Unity3D Engine Interface

When you first time launch Unity 5.6, you will be presented with an editor containing a few panels on left, right, and bottom of the screen. There's nothing to worry from these panels. The following image shows the editor interface when it's first launched:

Figure 1.7 Unity 5 Editor Interface at first launch

First of all, take the time to look over the editor and become a little familiar with it. The Unity editor is divided into different small panels and views that can be dragged around, resulting in a workspace that can be customized, according to the developer/designer's needs. Unity 5 comes with some pre-built workspace layout templates that can be selected from Layout drop-down menu in the top-right corner of the screen, as shown the following screenshot:

Figure 1.8 Unity 5 editor layouts

The layout currently displayed in the editor is the Default layout. You can select these layouts and see how the editor's interface changes and how different panels are placed in different positions in each layout. This book uses the 2 by 3 workspace layout for the game. 

The following screenshot shows the 2 by 3 workspace with the names of the views and panels highlighted:

Figure 1.9 Unity 5 2 by 3 layout with views and panel names

As you can see in the preceding screenshot, Unity editor contains different views and panels. Every panel and view has a specific purpose, which is described in the following section.

Scene View

Scene View is the whole stage for the game development, and it contains every asset in the game from a tiny point to any heavy 3D model. Scene View is used to select and position environments, characters, enemies, the player, camera, and all other objects that can be placed on the stage for the game. All those objects, which can be placed and shown in the game, are called as GameObjects. The scene view allows developers to manipulate game objects such as selecting, scaling, rotating, deleting, and moving. In simple words, Scene View is the interactive sandbox for the developers and designers. The Scene View provides some controls, such as navigation and transformation.

Transform tools

While developing games in Unity, you will place lots of game objects in the scene and their position, scale, and rotations, collectively called as transforms, are managed by transform tools. The following screenshot shows the transform tools:

Figure 1.10 Transform Tools

You can select any selected transform action from this toolbar and change the game object accordingly. The following figure shows the gizmo on the selected game object when a transform tool is selected:

Figure 1.11 Gizmos on game objects of transform Tools

These tools do exactly the same job as their names suggest; move for translation, rotate for rotation, and scale for scaling. The Rect tool on other side was introduced in Unity 4.3 when Unity got native 2D support and tools. This tool is only for 2D sprite objects for their position, scale, and rotations. You can also select these tools with keyboard shortcuts.

Scene View navigation

In the last section, we discussed how GameObjects can be transformed and navigated in the scene. But Unity being a 3D environment, it has an easy interface to view the scene from different angles, sides, and perspectives using mouse and keyboard shortcuts. You can observe the Scene Gizmo in the top-right corner of the Scene view. This gizmo is used to rotate the view according to the developer's needs. The following screenshot shows the gizmo of the scene:

Figure 1.12 Scene Gizmo for Scene View Navigation

Every view of the scene is shown in either perspective or isometric. There is also another view for the scene which we will discuss in the next section.

Scene View control bar

The control bar is shown at the top of the Scene View and it gives the developer more control to navigate through their scenes and create games easily. This bar includes options such as enabling/disabling gizmos, sounds, and selecting view modes. The important part of this bar is the 2D mode button, as shown in the following screenshot:

Figure 1.13 control bar of Scene View

The 2D mode button is a toggle button; when turned on; it disables the z-axis of the view and show the game from 2D perspective. It is highly used option while creating 2D games in Unity. On the right side of the bar, there is a text box for search. This lets developers search the game objects from the current scene and allows them to quickly work.

Game View

The Game View is the final representation of how your game will look when published and deployed on the target devices, and it is rendered from the cameras of the scene. This view is connected to the Play Mode navigation bar at the top of the whole Unity workspace, as shown in the following screenshot:

Figure 1.14 Play mode bar

When the game is played in the editor, this control bar gets changed into blue. A very interesting feature of Unity is that it allows developers to pause the game and code while running and developers can see and change the properties, transforms etc at runtime without recompiling whole game for quick workflow.

Game View control bar

Like scene view, game view also includes a control bar on top side of the view as shown in the following figure:

Figure 1.15 Game View Control Bar

The options perform the actions as their names suggest. The Free Aspect drop-down on the left side of the bar lets developers choose any specific resolution to test their games. These resolutions and drop down options vary on the selected platform. Developers can also add their own custom resolutions and screen sizes for their targeted devices. Unity also allows developers to specify aspect ratios as well to have an idea of how the game will run on various devices with the same aspect ratio. Unity is quite powerful and easily gives cross-platform support to make their games run better on most types of devices writing code only once.

Hierarchy View

The Hierarchy View is the first point to select or handle any GameObject in the scene. This contains every game object in the current scene. This is tree-type structure allowing developers to utilize parent and child concepts on the game objects easily. The following screenshot shows a simple Hierarchy View:

Figure 1.16 Hierarchy View

Project browser panel

This looks like a view, but it is called the Project browser panel. This panel is an embedded files directory in Unity and contains all the files and folders included in the game project. 

Following screenshot shows a simple Project browser panel:

Figure 1.17 Project browser panel

The left side of the panel shows a hierarchical directory, while rest of the panel is the files or as these are called assets in Unity. Unity represents these files with different icons to differentiate these according to their file types. These files can be sprite images, textures, model files, sounds and so on. You can search any specific file by typing in the search text box. On the right side of search box, there are button controls for further filters such as animation files, audio clip files, and so on.

Note

An interesting thing about Project browser panel is that if any file is not available in the assets, then Unity starts looking for it on Unity Asset Store and presents you with available free and paid assets.

Inspector panel

This is a most important panel for development in Unity. Unity structures the game in the form of game objects and assets. These game objects further contain components such as transforms, colliders, scripts, and meshes, and so on. Unity lets developers manage these components of each game object through the inspector panel.

The following screenshot shows a simple inspector panel of a game object:

Figure 1.18 Inspector Panel

These components vary in type including physics, mesh, effects, audio, and user interface. These components can be added to any object by selecting it from the component menu. The following screenshot shows the Component menu:

Figure 1.19 Components Menu

After covering some of the basics of the Unity, let's move on to the very first task developers do when creating a game; and that is creating an empty project. Let's discuss the configuration of empty projects in Unity for 2D games in the next section.

The game features a penguin that is on ice in very cool (pun intended) and that's why she is called penguin. In order to navigate through an ice field in the time of global warming, she gets a hold of a jetpack, which is tied on her back. The game uses a simple, one-touch system to control the penguin; when the player presses anywhere on the touchscreen, the penguin's jetpack is fired and penguin rises above the ground making a feel like she is flying for a moment. When the player lets go, the jetpack turns off and penguin falls. The game is continuously running in side view, so player is not required to control the speed of penguin. The player is only able to control the vertical movement of penguin by turning the jetpack on and off.

The objective of the game is to travel as far as possible, collect fish coins, and avoid obstacles such as zappers, missiles, and high-intensity laser beams.

In the next section, we will start the development of the Perky Penguin game. We will learn how to add the player, which in our case is a penguin with jetpack tied to her back, to the game.

Before we do anything, we need a player Sprite or image. For our Perky Penguin game, we have designed a penguin sprite. The following figure shows the penguin that is included as the player sprite of the game:

Figure 1.35 Penguin Sprite

To import an image in to Unity, right-click on the Graphics folder in the Project Browser panel and click on Import New Asset..., as shown in the following screenshot:

Figure 1.36 Import New Asset in Unity

These assets can be anything that is supported by Unity, such as images, audio files, 3D models, textures, materials, and scripts.

Unity shows all the images with nice previews. It must be noted here that if Unity is in 2D mode, then unity will show images as sprites and if mode is set to 3D mode it shows the images as textures. Figure 1.36 shows both scenarios. The following screenshot shows the image imported as sprite and the screenshot besides it shows image imported as texture:

Figure 1.37 Images as Sprites (left) and Images as Textures (right)

If the penguin image is imported as texture, then there is nothing to worry about. Select the image from Project Browser panel, and in the inspector change the Texture Type to Sprite and click Apply. It is shown in the following figure:

Figure 1.38 Change Texture Type of Image in Inspector Panel

After the assets are imported, which in our case is a single penguin image, we have to create a game object of player. Usually game objects are created by right-clicking in Hierarchy and selecting Create Empty as shows in the following figure:

Figure 1.39 Creating Empty Game Object

But, in order to create sprites as game objects, simply drag sprites from the Project Browser panel to Hierarchy or Scene View panels and a game object will be created with the name of image file which is penguin_fly.png here. This is shown in the following figure:

Figure 1.40 Creating Sprite Game Object

Now it's time to configure the penguin_fly game object of Hierarchy to get used in the game. Now select the penguin_fly object and make following changes in the Inspector panel.

Figure 1.41 Adding Circle Collider 2D

Figure 1.42 Adding Rigid Body 2D

The following figure below shows all the steps performed on the penguin game object:

Figure 1.43 Penguin Inspector Settings

Starting from position, we have set the position to zero just for testing purposes. We will change it later when we put penguin at its initial position. The Sprite Renderer component is already added in the penguin game object because penguin game object was created from sprite by dragging it from Project Browser panel. The Sprite Renderer allows any game object to show an image on the screen from any sprite. In order to make any game object to react to physics collisions and get collided with each other, game object requires collider component in it. We have added Circle Collider 2D on the penguin object. You can choose any type of collider from the list. But it is recommended to choose the collider which is very light and fills the whole colliding area. The following figure shows the penguin with different colliders applied to it:

Figure 1.44 Penguins with Different Colliders

Using complex colliders like Polygon Collider 2D makes it harder to detect collision for the physics engine to detect collision, which in turn, creates a performance penalty. Finally, in order to apply gravity on the penguin, we have added Rigid Body 2D component. Rigid Body 2D allows any game objects to behave to the gravity, friction, physics kinematics and so on. We have check Fixed Angle to on state of the Rigid Body 2D. If this is set to off, then penguin will also rotate due to wind, friction, gravity, or any other force applied on it. So in order to avoid her to rotate while jumping, we have set Fixed Angle as checked.

When you run the project, you will notice that penguin will fall down on the screen. It is because of the gravity is pulling penguin downwards and it goes off the screen. The Gravity Scale value, which is 1 by default, decides the gravity of the penguin. If we remove or disable Rigid Body 2D component, then penguin will never move. So, it must be noted that without rigid body no force and collision will be applied on the game object.

After setting physics components and position on penguin object, it's time to define some logic behavior of the penguin. The game's requirements are to let penguin fly through its jetpack when screen is touched by player and penguin will fall when touch is stopped. These kinds of logic are defined in Unity through scripts. Unity supports 2 kinds of scripts; C# and JavaScript. You can use any of these scripts. Even you can also use few files in C# and few other files in JavaScript in the same project. Throughout this book, we will do all the scripting through C#.

Figure 1.45 Adding a C# Script

Figure 1.46 A C# Script File in MonoDevelop

Figure 1.47 Adding C# Script on Penguin GameObject

Now, as the script is applied on the penguin game object, let's write some logic and code to make the penguin fly. Open PenguinController.cs file from project browser panel by double-clicking it in MonoDevelop. The code which is already written looks like the following screenshot:

        public float jetpackForce = 75.0f;

Figure 1.48 The jetpackForce Field in the Inspector Panel

        void FixedUpdate()
        {
            bool jetpackkActive = Input.GetButton ("Fire1);
            if (jetpackActive = true) {
                this.GetComponent<Rigidbody>().AddForce(new Vector2(0, 
                jetpackForce));
            }
        }

Following is the whole PenguinController.cs file's code: 

Figure 1.49 Gravity Scale of Penguin (left) and Gravity of Physics2D (right)

We will change the Gravity value of Physics2D settings to -15. You can open Physics2D settings from Edit - Project Settings - Physics2D menu.

Now run the game, and you will notice the penguin will fall slower than before. On clicking many times, you might notice that penguin gets out of the screen. This kind of behavior in the games should be avoided. So, in order to limit the penguin within the screen bounds, we will add floor and ceiling in the game. Let's see how it's done in the next section.

Adding floor and ceiling is quite simpler job. We will create an empty object first. It should be noted that we are not importing any images or sprite assets in the scene, because we only need boundaries not the visuals of those about how these will look. Here is how we create our floor object.

Now you should be seeing a green rectangle on bottom of screen. This is the box collider of the floor and when you run the game, the penguin will never fall off the screen and it will stop when collided with the floor.

Similarly, now add ceiling game object with the name ceiling and its position of (0, 3.25, 0) and its scale of (14.4, 1, 1). Apply Rigid Body 2D component on the ceiling object, and now run the project. You will observe that penguin now never leaves the screen and it is limited between the upper and lower parts of the screen.