Introduction
A significant rise of mobile smartphone users throughout the world have been witnessed within the last few years. With the introduction of iPhone, Android, Blackberry and their rapidly growing applications, the popularity and growth of smartphones are increasing day by day with a significant percentage. According to a BBC report, one in three people in the United Kingdom use a smartphone. The worldwide usage and extreme popularity of mobile devices has created an essential industry for mobile applications and games that continues to grow extremely rapidly.

There are tons of different kinds of mobile devices available now in the market and due to this availability, it is very important for a developer or a development company to target the right mobile platform and development environment. To maximize the sale or popularity of an application, cross-platform development is necessary and this is significantly important for mobile game or application development. Portability across different platform will definitely enhance a broader category of users.

Over the years, development of mobile games involved hard work. Professional software developers and programmers were hired by companies to develop games and it also consumed a great amount of time to bring perfection in a game. But recently, it is seen that independent developers and also people with very little or no programming knowledge are building games and application on a regular basis and many of those games were not only being played but also received tremendous amount of success as well. For example, 14 year old Robert Nay developed Bubble Ball which literally knocked the famous Angry Birds down from top position.

In this study, review will be conducted about a scripting language called Lua, which is used to develop games and applications and a review about Corona SDK, which is a software development cross-platform engine that uses the above scripting language, Lua to allow developers build applications for smartphones efficiently and quickly.

Mapping the Territory

There are several different types of scripting languages available to develop applications, such as, Perl, Python, Ruby, JavaScript, Lua and many more. In addition, different types of game platforms are also available, such as, Corona, Cocos2d, GameSalad, Unity3d, jMonkeyEngine and more.

This research is mainly based on Lua and Corona where the following segments will be discussed.

 Overview of both Lua and Corona SDK.
 Evolution of Lua.
 Why Lua has been considered as a preferred scripting language when it comes to develop games?
 Features provided by Lua.
 Practical use of Lua.
 Why Corona is used and liked by most developers?
 Features and functionalities provided by Corona.
 How Corona has become successful as an application development platform.

All the discussions that will be made in this study will contribute towards the design stage of this project, where by using Lua as a scripting language and Corona SDK as the platform a simple quiz based game will be made for mobile devices for young and also adult as a target audience.

LUA
Lua is a scripting language created in 1993 by the Computer Graphics Technology Group (Tecgraph) at PUC-Rio, the Pontifical Catholic University of Rio de Janeiro in Brazil. The creators of Lua were Roberto Ierusalimschy, Luiz Henrique de Figueiredo and Waldemar Celes. Although three of them were involved in the creation of Lua but the chief architect of Lua is known to be Roberto Ierusalimschy.
Since Lua was created, it has been adopted by various industrial organizations and used vastly in challenging applications such as robotics, image processing, distributed business literate programming, extensible text editors, bioinformatics, Ethernet switches, web development, finite element packages and many more. On top of all, Lua has been considered as a leading scripting language for game and application development in the gaming industry.
According to the creator of Lua, Ierusalimschy, Lua is widely used in the above fields because of its simplicity, extensibility, portability and efficiency that benefit the applications. Lua is designed in such an efficient way that constituent unit of other languages function cooperatively which means that Lua is integrated with programming language such as C and also other conventional languages which provide significant benefits.

According to Ierusalimschy, Lua is a tiny and simple scripting language and it has a very safe working environment, automatic memory management and it also provides very good facilities for controlling and handling strings and other types of data with dynamic sizes because of the factors involved with C, because of the integration, Lua does not copy C, instead it depends on C for various tasks, such as performance, low-level operations and good interface with third-party applications or software. However Lua provides functionalities that C is not very efficient of doing them such as, dynamic structures, good distance from the hardware, simplicity of debugging and testing mechanisms, error handling, garbage collection and no redundancy issues.

Lua is a scripting language with some powerful unique features that makes it the best choice over other languages to use for developing applications or games. The features are:

Extensibility: Due to the wonderful extensibility, Lua is considered as a building block for languages which are domain specified. Lua has been designed from scratch to be extended, both through Lua code and also through external code of C. External libraries are used by Lua to perform most of its basic functionality. Communication between Lua and C or C++ is very easy and convenient, and Lua has been used integrated with various other languages as well, such as FORTRAN, Java, Smalltalk, Ada, C# and also with other scripting languages, like Ruby and Perl. (source)

Simplicity: Lua is a simple, small and fast language and because of its simplicity, it is very convenient to learn and understand Lua. Because Lua is so small that its complete package which includes the source code, manual and binaries require a size of only 150 KB or less. (source)
Portability: The portability of Lua makes it stand out because it is capable of running on most of the platforms, such as, Windows, Mac, Linux/Unix, BeOS, QUALCOMM Brew, MS-DOS, RISC OS, IBM mainframes, Symbian, PalmOS, ARM processors, Rabbit processors, PlayStation platform, XBOX platform, iOS, Android and more. All of the above platforms are different but the source code for all of them is the same. No special compilation is required for Lua in order to use the code for different platforms because Lua uses ANSI/ISO C compiler and hence runs on any platform. (source)

Efficiency: Lua is very efficient due to fast compiling and fast executing of applications. Independent benchmarks show that Lua is one of the fastest scripting languages. (source)

One of the main reasons for adapting Lua by many software industries is that it is not bound by any restrictions and limitations as it is an open source free programming language. According to Brian Burton, due to the state of being fully developed and the freedom Lua provides, Lua has been evolved to be one of the smallest, fastest and most commercially flexible languages of its kind. Lua can be used on almost any hardware device because of the greatest degree of portability which makes Lua superior in terms of force or power and widespread. Many popular and challenging commercial applications have used Lua because of the speed, reliability and stability and one example would be the Adobe Photoshop Lightroom where signification chunks of the application are written in Lua.

Lua made a big impact internationally with the adventure game called Grim Fandango which released in 1998 by LucasArts Entertainment Company; an American based Video Game Company. Then Lua gained a worldwide exposure and recognition by the hugely demanding multiplayer role-playing game World of Warcraft by Blizzard Entertainment.
Since then Lua has been used extensively for scripting, internal logic and prototyping, programming and more in very popular and highly rated games and applications such as Half-Life 2, Far cry, SimCity 4, Supreme Commander, Garry’s Mod, Psychonauts, MySQL Proxy, Wireshark - The world’s most popular network protocol analyzer (Lua is used for prototyping and scripting), MacroMonkey, Adobe Photoshop Lightroom and many more.
Over the past few years handheld devices have made a solid platform for themselves in terms of gaming and applications. People are playing more games in handheld devices than in traditional platforms. Competitions between mobile companies are increasing every second as various commercial organizations trying to set their position by developing latest devices and new technologies.

Leading companies like Microsoft, Nokia, Blackberry have led the market in handheld devices for sometimes now with their massively popular operating systems such as Symbian, Windows Mobile for handheld and Blackberry OS but a new era has taken place with the creation of Apple’s iPhone and Google’s Android devices where the increasing popularity of iOS and android market are taking over the traditional handheld systems discussed above.

According to Brian Burton, recent iOS and android based platforms provide a mixture of similarities between gaming consoles and integral or embedded platforms. Leading game development companies, Electronics Arts and Tapulous (now owned by The Walt Disney Company) have used Lua to develop applications for iOS and android. Lua has been used in the bestselling and most popular iPhone games like, Angry Birds, Tap Tap Revenge 3 and Diner Dash.

Corona

Ansca Mobile is a mobile software company that was created in 2008 at Palo Alto, California by Carlos Icaza and Walter Luh and both of them used to work for Adobe. In 2009, Ansca Mobile developed a software development kit to build mobile phone applications for iOS and android based devices called Corona. Corona SDK is a software development kit that entirely uses Lua to allow people to develop applications and games for iPhone and android devices easily and quickly.

According to Ansca Mobile, Corona is world’s number one game development platform which lets developers build high quality games without spending a massive amount of time and effort because of its powerful framework and APIs.

There are many game engine platforms out there which also let users develop good interesting applications for iOS but Corona which is built on top of OpenGL, OpenAL, Box2d and Lua and it runs at an existence speed using native iOS features, such as, multi touch, accelerometer, gyroscope, camera, GPS, Google Maps and more.

According to an NPD Group report android and iOS devices are gradually taking over all smartphones. In general, smartphone sales are increasing rapidly worldwide and one of the main reasons behind it is the tons of amazing applications that are available in application stores for the specific smartphone. Therefore a major challenge for smartphone companies is to provide with applications to the application market as the number of smartphone users grows. Another issue the software development companies face is to provide their applications that can be used across multiple platforms. Cross-platform development now is a major necessity and as a result developers throughout the world from large scale companies to independent programmers creating their own applications will have to think about cross-platform development to give their products the largest possible exposure.

In relation with the above discussion, Corona provides cross-platform development. According to the creators of Corona, it has the only complete solution for developing across multiple platforms, OS versions and various screen sizes. It is not required to write and compile code separately for different platforms; instead the application is needed to write just once without changing the code and then it can be built to different platforms. Corona adjusts and scales the contents, screen sizes, resolution and application display automatically for different devices.
Corona uses OpenGL, a powerful graphics rendering engine that allows users to add high resolution images, draw lines, polygons, circles and rectangles. With GPU accelerated graphics, Corona lets developers build rich graphical interactive applications and sophisticated games.

Corona’s event system also delivers some powerful features which include multi-touch handling, animation handling, GPS and accelerometer functionality and custom events handling. Other Corona features include playing audio and video clips, a cryptography library, networking using the LuaSocket library, and access to SQLite databases (using LuaSQLite). There is some access to native widgets including textfields, alerts and activity indicators. Corona also lets developers to connect to social networking sites like Facebook and twitter by using the Facebook/twitter API which provides a library for communication. Corona also allows developers to add OpenFeint social gaming feature into their application/game, such as, view leaderboards. A web layout can be added in an application to perform task such as login or feedback screen.

Another worthy functionality of Corona is its physics engine. To give objects or items a real life-like appearance, a physics engine is used in a game platform. Corona includes Box2D physics engine, one of the world’s best 2D physics engine that simulates the physics of objects. Using Corona’s Box2D engine, a powerful and attractive game can be made.

Games made in other platforms, such as, Adobe Flash, GameSalad or Appcelerator Titanium run at a fairly low speed in comparison with games made in Corona and that is also a significant aspect for developers.

Corona also provides functionalities that help developers create applications other than gaming. For example, XML parsing, manipulation of file management and full database handling using SQLite are also supported by Corona SDK.

Corona provides a library that contains over five hundred API’s. API is an Application Programming Interface which is a set of rules or protocols needed to build applications. Due to the increasing number of API’s, Corona is loved by developers as it cuts down a lengthy amount of time during the code writing process.

The ability to cut down programming time by using the Lua scripting language is a major advantage of building applications with Corona. According to the creators, if a comparison is to be made between code written in Lua and code written in Objective-C, it is seen that to accomplish a task, hundreds of lines of code needed to write in Objective-C, whereas the same task can be accomplished by writing only a few lines of code in Lua and while setting or removing an object from the memory location, it is not required for the developer to keep a track of them as Corona SDK is capable of keeping track of its own memory management model.
There are also a number of community resources that can significantly speed up development time. For example, scripts, buttons and labels. (1890)

Display an OpenGL image in Corona: Few lines of code.
1. --Display "myImage.png"
2. display.newImage("myImage.png")
Display an OpenGL image in Objective-C for Apple iPhone SDK: Over 300 lines of code.
1. // Display "myImage.png"
2.
3. // ----------------------------------------------------------------------------
4. // OpenGLESTextureAppDelegate.m
5. // ----------------------------------------------------------------------------
6.
7. #import "OpenGLESTextureAppDelegate.h"
8. #import "EAGLView.h"
9. #import "OpenGLESTextureViewController.h"
10.
11. @implementation OpenGLESTextureAppDelegate
12.
13. @synthesize window=_window;
14.
15. @synthesize viewController=_viewController;
16.
17. - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
18. {
19. // Override point for customization after application launch.
20. self.window.rootViewController = self.viewController;
21. return YES;
22. }
23.
24. - (void)applicationDidBecomeActive:(UIApplication *)application
25. {
26. /*
27. Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
28. */
29. [self.viewController drawFrame];
30. }
299. glLoadIdentity();

300. glMatrixMode(GL_MODELVIEW);

301. glLoadIdentity();

Above given is a comparison between Corona & Objective-C.

The only thing that developers find a bit annoying with Corona is the subscription charge related with it but it does not mean that Corona cannot be used at all without paying. Corona SDK is free to download from Ansca Mobile and applications and games can be made easily with Corona by using all of the main features that it provides. The only things that Corona SDK does not allow to do without a membership fee are to create builds for cross-platform and to publish an application to the application store. (1980)
Success Stories
Corona is rapidly becoming one of the most demanding and powerful game engine platform to develop games and applications for cross-platform devices. As developers are using Corona SDK day by day its popularity is increasing and it has also brought some major successes in the development of games in the application market.
One of the major success stories is that of the game called Bubble Ball, developed by only a 14 years old boy named Robert Nay from Utah, United States. The game has been developed and uploaded to Apple’s iTunes application store and within a very short period of time, Bubble Ball created a revolution in the application market. With a massive number of more than ten million downloads, Bubble Ball knocked out the famous and prestigious Angry Birds from the top position.
Another highly successful game created in Corona was Doodle Dash by Jonathan Beebe who learned Corona in less than ten days and created the game which became an instant hit and gained a prestigious top 25 status in the application market.
According to a press release(June, 2011), Ansca Mobile declared that the game Blast Monkeys by Yobonja made it big in the Apple and android market by reaching top spot in the action and arcade category. Following the game’s success, Carlos Icaza, co-founder of Ansca mobile stated:
”We are excited to see Yobonja’s success on both the Android and iOS platforms. We have worked hard to make Corona SDK the absolute best framework in which to develop rich, cross-platform mobile applications and it is gratifying to see our community grow and succeed”.
Another success story involves with Warner Bros.’s high star-cast film called Dolphin Tale that released in the latter half of September this year. The producers of the film decided to make a complete cross-platform game to market the film for iPhone, iPad and Android market. The task was given to Corona and as a result a full game had been produced in less than two months which is now available in application stores. Later on, the film’s co-screenwriter, Noam Dromi said that the Dolphin Tale application would not have been possible without Corona. Dromi also stated: “We were able to do it for considerably less cost while not skimping on quality”. (375)

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Conclusion

In this Literature Review, several aspects of a scripting language and a development platform have been discussed. Features and functionalities of Lua and Corona SDK have been looked through. It has also been learnt that when it comes to mobile game development, portability is the key factor in order to reach a broader audience and largest possible market. Corona SDK is a relatively simple and easy to use game engine platform that uses Lua entirely as the language to write codes and both Lua and Corona are very portable and are supported by different platforms.

It has also been discussed that Lua is a powerful scripting language which is used in many areas and for several purposes, such as, coding, scripting, prototyping and many more. Because of Lua’s extensibility, portability, simplicity and efficiency, Lua has been liked by many developers and since its creation Lua has been used in many top-notch and demanding applications.

As a game engine platform, Ansca Mobile’s Corona SDK contains an integrated simulator for cross-platform devices. Integrated Box2D physics engine, debugger, and a rapidly growing library of APIs and sample codes make Corona a preferred choice for developers in developing iPhone, iPad and android based games and applications.