Related
I saw this thread comment on 2D engines at [stackoverflow]:2D Cross-Platform Game Development Engines
I am interested in LibGdx (Java) and Citrus Engine(Action Script). What would you choose?
I can only talk for LibGDX, but I can honestly say that it is the best game engine I've used so far. Let it be features, ease of use, or active community, LibGDX has it all.
It supports a lot of platforms, like Desktop, iOS, Android and others. It's really fast and supports both 2D and 3D as well as sound and physics engines which are included (Box2D and bullet physics).
There are tools like a particle editor, loaders for several map editors and UI skins. Join the official channel #libgdx on freenode (IRC) if you have any questions and have a look at this trend.
You often see that a new game will be released on Xbox 360, PS3 and Windows PC.
How do gaming companies do this? Is it a common source code compiled using different compilers? Are different source codes actually required?
There's an example of this phenomenon described in this news article.
Generally speaking, the vast majority of multiplatform "triple-A" titles are implemented on top of an engine such as Unreal, Source, or other smaller engines. Each of these engines is custom-implemented and optimized for each platforms and may use a lower-level API such as DirectX/OpenGL which in turn uses the console. Each of these engines also has plug-ins for platform specific stuff (e.g., motion controls) that interact with the official drivers or APIs of the hardware.
Many of these engines support their own scripting languages or hooks for many things, so it is write once.
For example, take a look at the unreal engine:
http://www.unrealtechnology.com/technology.php
Most of the biggest engines, like Unreal are so flexible and robust that they allow developers to write all kinds of games. For instance, the Unreal engine was used not only for shooters, but also for shooter-RPGs like Mass Effect.
Remember that most of the manpower in making games is devoted to graphics, set designers, audio design, level design, etc., and there are custom editors for all of that. Many of the set pieces are usually programmed via scripting languages. Only a small portion of folks in gaming companies actually write code in low-level languages like C.
The engine takes care of this by providing a platform independence layer.
Things that varies between platforms for instance graphics library. threading, clock and filesystem etc; are implemented for each platform in the game engine.
I can make a call to the engine to render a 3D model consisting of triangles.
The engine in turn render this model by calling down into the platform independence layer which uses an implementation for the currently used platform.
There are two ways game companies do this:
1) Writing/using a multiplatform engine
2) Porting a game
A multiplatform engine will feature abstractions for platform-specific actions (making a Windows API call, rendering in DirectX vs OpenGL, etc etc) so that all of the work can be done once, then built for both machines. Usually it's a matter of writing simple wrapper methods for things like Direct3D calls and what not. Most newer game engines are being built from the ground up with multiplatform support. Others are adding multiplatform support.
If a game engine isn't multiplatform, it has to be converted to run on the target platform. This is usually a two-part operation. First, all of the API calls and interfaces with the hardware need to be redone for the target platform. The second part involves debugging and optimizing the game for performance. Typically a direct port will not perform very well, as the code will feature platform specific optimizations that do not apply to the new target platform.
For various reasons, ported games can suffer from performance issues, usually in spite of watered down visuals. Take a look at The Orange Box on PS3 or CoD: Modern Warfare for the Wii to see two examples of ports gone wrong. For the OB, Valve outsourced the task of porting the game(s) to EA. In the second instance, Activision decided that it made more sense to port a game on an engine designed for more powerful hardware over to a weaker platform instead of building the game on top of a new engine designed to get the most out of the Wii.
Many places will have separate teams responsible for different versions. That is why you always see some small differences. However, if a portable language is chosen, these teams may be able to trade code around.
If the company as produced a game engine, developers can just develop on top of that, leaving the engine to handle the cross platform specifics.
I'm guessing that the art/media department is that same for all platforms.
Actually, there are some frameworks that are meant to be able to run on multiple platforms.
For example:
The XNA Framework can run on Windows, Xbox, and Windows Phone with almost the same code base. (About 90% the same C# code can run on all of the platforms.)
Unity 3D supports PC, MAC, browsers, the iPhone, Wii, and it will soon support Android, too.
There are other such frameworks as well.
Also, most of the popular game engines (eg. Unreal, etc) are ported across multiple platforms.
This is often accomplished with a virtual machine that handles non-time-critical game mechanics and an abstraction layer for time-critical but platform-specific operations.
The particular methods are highly proprietary, secret, and are the among the most valuable assets of the game maker.
I remember reading an interview (or perhaps it was a .plan file/blog) John Carmack gave a few years ago. He was discussing developing for multiple platforms. (If memory serves this was around the time they were releasing titles for mobile platforms) The advice he gave was to always target the platform with the lowest system specs you plan on supporting first. His reasoning was that it is far easier to scale up than down. If you focus on the latest high end graphics you're likely to wind up depending on features only available on the high end. Making it very difficult to scale back for mainstream and lower end systems. Anyway, I thought it was pretty good advice.
This is all a guess because I don't work for a company that makes console games, but speaking from experience as a software developer what I imagine happens a lot of times is that external libraries are used against source code that's written in a common language, such as C++ or something. A lot of the core game code (game loop, physics stuff, etc.) can be used because the syntax is the same with the library across platforms.
However, there is a large degree of code that has to be written (and tested) that is unique to the platform. For example, most (if not ALL) graphics card-related code would have to be different for the Xbox 360 vs the PS3.
This allows for a large degree of portability on core functions and then the UI stuff and graphics-related stuff is platform-specific (not always for the UI).
Also, large game companies have 100s of developers working on a project, so they have a lot more resources than some indie developers might.
It's never perfect though. You always have to port SOME code. Unless you're using Adobe AIR, but your game is for consoles (and who uses Adobe AIR to develop REAL games?)
Game companies use commercial middleware, like RenderWare which do not come cheap. Most game platforms also support a C++ environment for code to get compiled on. Additionaly, most consoles come with a Development version (Playstations do) and there are simulators to test most code on. This middleware is now owned by EA (which is like the giant player on the field). Creating 3D games aren't just framework. Most of the game comes from a design document, which documents the flow of the game and game play. The artwork is done in other software (Maya and Lightwave for example) and the 'models' which are the game characters.
Even though it might look horrific a lot of work, when it comes to coding, it isn't that big of a deal. Writing the core functionality takes a week or eight, the rest is more in design and planning. Just remember that 3D is only 10% of the overall game. These are my two cents as a former game developer.
Not necessarily video game related, but the best walk through I've seen for doing multi-platform software was in GOF (http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612). Read the case study on the windowing system.
I would say "largely they don't." All the money is in Windows or in consoles and a lot of the consoles want an exclusive license. I have seen a few ports but they're always a separate code base branched from a previous version.
Very often they use #define (for example in C++ code) so before the compilation for the specified platform the proper code is included or used. In bigger projects sometimes the parts of a game are totally different and written in different IDE's and compiled in different (platform specific) compilers.
Example from my experience:
When I was working on a game for Nintendo Wii, we were using Torque game engine. We were programming on PC's and compiling code for PC's. When some functionality was ready we used Metrowerks CodeWarrior (with special set of libraries etc.) to compile it for Nintendo Wii, send it to the devkit and then run from the Nintendo Wii console.
This question is directed to anyone out there that is just starting in hobby game development. The first thing that comes to ones mind is:
Which language/framework should I use?
List of solutions:
Adobe Flash -> done
Allegro
Apocalyx
Blender Game Engine
Blitz3D
Devkit Pro
Game Maker
Gosu
IndieLib
jMonkey Engine -> done
Microsoft Silverlight
Microsoft XNA -> done
Multimedia Fusion / Games Factory
OGRE -> done
pygame -> done
pyglet -> done
RubygGame
SDL -> done
SFML
Torque 3D
Unity 3D
Custom -> done
Answer template:
Framework Name (Linked)
Pros:
Pro1
Pro2
...
Cons:
Con1
Con2
...
Microsoft XNA Game Studio
Pros:
Uses .NET languages; managed memory, ease of the Visual Studio environment, etc.
Good mix of high-level and low-level
Supports both 2D and 3D very well
Is proven; look at the Xbox Live Arcade, all of those games are made with XNA
Games can be easily run on a networked Xbox
Cons:
Uses .NET languages; can't use Java, C++, etc.
Not too many resources (i.e. books) out yet, though it is easy to learn and use so that may not be an issue
Windows-only. Mono (on Linux) doesn't support XNA at all.
XNA 3.0 was released less than a year after 2.0, and now we're at 3.1; frequent changes like these can hinder documentation, i.e. books get outdated quickly and many things break when upgrading a 2.0 game to a 3.0 game.
As of 2014, discontinued.
If you have the time, do it all yourself. It's worth the experience and you'll learn a lot, instead of how to work with framework X . ;^)
Pros
Full Control
Strong Learning Experience
Consistent code between game engine and program
Tends to be well-suited towards the application it is applied towards.
Supports any language/environment
Cons
High difficulty
No online documentation
Generally, less generic. Harder to apply to other games.
Harder for other people to use.
Probably buggier than more popular frameworks.
Not well-tested.
Harder to get help.
jMonkeyEngine
Pros
Uses Java; managed memory, highly supported in many mature IDE's (Eclipse, NetBeans, etc.), highly portable
Good mix and high-level and low-level
Modern 3D scenegraph
Built atop LWJGL, a very mature and well-working game library
Very lightweight; doesn't add very much overhead
Built in 3D model loading in a variety of formats.
Built in modern node-based 3D scenegraph.
Easy to use.
Open source; constantly evolving and improving.
Includes culling, collision checking, etc.
Has the option to save and read its own ultra-compact, ultra-fast binary model format.
Full list.
Cons
Uses Java, so compiles JIT and can therefore be a bit slower than C++ and other options.
Hasn't been used in many commercial apps (and therefore not as "proven").
Has no attached editor of any kind, everything must be done in pure code.
Difficult to do 2D games (for that you could try Slick).
pygame
Pros:
Easy to get started and create something visible.
Cross-platform.
Lots of open source games available to inspect the source.
Python language's pros (flexibility, dynamic typing, strings/arrays/tuples, etc.).
Cons:
Performance-wise does not scale to very large games (which hobby game development rarely is).
Mostly suited for 2D, although 3D is possible.
Difficult to distribute as closed source.
Also SDL could be inserted as pros and/or cons.
OGRE (Object-Oriented Graphics Engine)
Pros:
Tons of 3D features
Cross-platform, uses DirectX or OpenGL
Plugin architecture for even more features
Does not try to be an everything-engine, only a graphics engine (doesn't even try to handle input, as many graphics libraries tend to do)
Cons:
Uses the Singleton pattern
Very hard to do 2D or primitive rendering (individual polygons, lines, etc)
Tons of code makes the learning curve quite steep
pyglet
Pros:
Low difficulty
Cross-platform
OpenGL accelerated graphics by default
Further OpenGL graphical enhancements easy to add
Python language
Cons:
Less well-known than pygame
Game 'loop' is a bit unconventional
OpenGL knowledge required for advanced graphics and to maximise performance
SDL
Pros
SDL officially supports Windows, Mac OS X, Linux, iOS, and Android
It is used by video playback software, emulators, and popular games including Valve's award winning catalog and many Humble Bundle games.
Open source
SDL is written in C, works natively with C++, and there are bindings available for several other languages, including C# and Python.
Cons
No special IDE like Unity
A bit low-level
The pros of any framework (gaming, web, etc.) is that they remove the unnecessary boilerplate code you'd have to normally write.
The cons often come up later on, once you want to go beyond the capabilities of the framework it can become very difficult. With many of the more complex frameworks, extending their functionality to make it do something it wasn't designed to will results in you having to write a lot of your own boilerplate code.
just starting in hobby game development
You should program a few games before attempting your own framework, otherwise you don't know what to put in it and how to write it. You'll end up endlessly rewriting it to "get it right", when really there are lots of good (and bad) ways of doing it, depending on what it is used for.
"Frameworks" can also be a pain, as they offer a partial solution to a problem. E.g. you just extend a few classes and boom, you have a game. But if your game doesn't suit the framework design you just end up fighting with it and hacking it. The "toolbox" approach tends to be a better approach as it just supplied functionality without forcing you too much into how you should use it. E.g. the standard C libraries are are toolbox and don't force you to structure your code in a certain way.
To start off with you have to ask yourself:
what sort of games you'd like to write.
what you'd like to develop for?
Web browser?
Facebook?
PC?
PC and Mac? i.e. cross platform
Console?
iPhone and iPad?
which language you'd like to use (but this may be set by the platform you chose)
The learning curve for writing games can be quite steep as you might have to learn:
how to program in a new language
how a new API works
how to do the graphics and sound
how to debug it
perhaps how to hook it into other system
Don't be put off it this sounds like a lot of work! The key to writing good games is sticking it out and having the determination to carry on and finish. Have you seen the film, Indie?
My advice:
Start simple - There is a lot to learn, if you take on too much to start with you will be scared off and think it is to hard. So...
Easy language - You'll hear lots of people ranting on the internet about how great certain languages are. Well, they all have their pros and cons. Some are easier to learn that others. E.g. Python or Lua are quite easy to learn. They are scripting languages, which are a lot more forgiving and less complicated to games together with. They don't have things like pointers, memory allocation, etc to worry about.
Python tutorial.
Lua has a tutorial (which I wrote!)
Just make a game! - You'll hear other people talking about patterns and singletons and data driven design etc. None of that matters when you start out. You aren't trying to impress anyone with your code. People will judge you on the end result not the code! Trust me, some of the best games you've played on console etc have terrible code!
Use a small, well maintained library. I'll make it easy, there are other choices, but:
if you want to choose Python (a good choice!) use pygame. Use Eclipse (for Java Dev) with PyDev. Magic and free!
if you want to use Lua (a good choice!) use Love
Look for other game examples - Pygame has tons of examples and games using it. Check the license and if you are allowed, just rip the code. Patch, splice, but put a comment about where you got the code, it is polite, and may be necessary according to the license. Don't ignore the licensing.
Look at Ludum Dare. Tons of great examples and source code to see how it is done quickly.
Then once you have made a few games consider the more complicated libraries and languages. Then you can ask more specific questions about how to solve certain problems. Have fun!
Flash
Flash is a great tool for those who have limited programming or art experience, but want to start cranking out a game.
Pros:
Symbols make graphical creation and manipulation very easy
Symbols have built-in bounding boxes; bounding boxes have built-in collision detection
Ports easily to web
Built-in layers and display architecture make displaying content simple
Lots of support, documentation, libraries
Vector art is easy to create
Cons:
Relatively slow
No method or operator overloading
Requires a purchase, either Creative Cloud or buying Flash outright
Pixel art must be ported in, which can be aggravating
I highly recommend flash if you have access to it, its one of the programs I use most often.
Pro's for XNA in my opinion are that XNA apps can run on Xbox360 in addition to PC, and you can pick your favorite language from anything supported by the .NET Framework - which is quite many.
i've been making web app's and working with various server side language like php, ruby, perl for a while now. I've always been curious about game development, it's actually what I set out to do but I ended up in web development. I am trying to transition in to GD, but I cannot help see games from a web development POV.
GD = Game Development
WD = Web Development
Technical Questions.
How do you design UI in games? in WD you have CSS, and need minimal graphics to create a quick menu. are there similar tools or concepts in GD ?
How do you deal with storing data ? Do you use flat text files? Or is there something like MySQL or sqlite that you use to store information about objects, users, and etc ?
What game engines is commonly used ? Are there any that use scripting languages ? I only know VB and basic understanding of C.
With the proliferation of Iphone and Android, is J2ME being phased out for mobile phones ?
open 3D web is coming. What is your thoughts on having 3d applications running natively from your browser ?
What tools make it easy for creating 3D objects, levels, game environment, and animating characters and so on ?
Where can I find out more about how server/client, client/client, and MMORPG networking works ?
Where can I get or find generic or commonly used game flows ? for multiplayer ?
How do you deal with physics? Is there freely available algorithm or library that you can use ?
How are real time cutscenes made in games ?
Market Questions.
Which market should you enter? Mobile, iphone, wii, PSP, DS, android , ps3, PC etc.
Shouldn't you always enter mobile market, as it is easy to make small games on your own yet sell a lot ? Are there any resources where i can find more about each markets ?
What is your thought on Steam content distribution ? Is it the distribution model of the future ? Whats wrong with the traditional publisher/distributor model ? How does the traditional model work exactly ?
How big is the web games market? ex) Flash games.
How is game development different from any other software development or web development ?
I have a lot more....but those are the ones that I have been thinking about lately.
Thank you very much for reading !
UI Development
Depends on the game- is it animated, or a board-style game? Generally, UI assets are created as images, sprites, or storyboards.
Data
Again, depends on the game type. Realtime games need FAST access, so you want to store your data in a local database and cache it as much as possible. Local file-based databases tend to be the norm, either custom or off-the-shelf, such as SQLLite.
Engines
There are tons of engines out there for 3D, board, etc. Popcap has made their C++ game engine open source. Others include Unity, Ogre3D...
J2ME
I wouldn't target this platform for games.
Don't know much about "Open 3D Web" but it sounds very browser-dependent, so mileage may vary across browsers.
You can play with 3D with Google Sketchup and Caligari Truespace. Truespace was bought by Microsoft and made free.
Again, tons of engines out there for networking. Example: Microsoft's XNA framework has some networking bits you can leverage.
Not sure what you mean there.
There are physics engines built into some of the gaming engines I've mentioned, and external ones you can use.
Once upon a time, realtime custscenes were pre-rendered with 3D Studio Max or Maya. These days in-game rendering is often good enough for cutscenes: look at the latest Halo 3:ODST game. All cutscenes use the in-game engine.
Market
I looked into game development earlier this year. Casual games look to me like a growth industry- high volume, relatively low development cost. Big Fish Games for the PC is a good example there- they publish a few titles and resell most.
I think mobile game development is a huge potential market but the barriers to entry are high because it will be a crowded space. iPhone games are the 800lb gorilla but Android is coming up. PSP and others have a limited audience and are notoriously difficult.
The most important thing I learned in my research is that game development is a labor of love. It's hugely multi-disciplinary: you need programming, art, concept, production. It's more like making a movie than anything else. It's also rough to make a profit because of all that overhead. If you want to get into it, I recommend joining a game developer to learn the business. Once you have experience you can carry it forward to larger gigs at larger publishers. Eventually you can get to work on a major AAA title, after which you can really write your own ticket.
I'll stick to answering the technical questions:
1 - UIs are usually completely bespoke, with nothing resembling a standard in the same way that HTML/CSS is a web development standard. Some people use ScaleForm which is based on Flash but that is by no means common.
2 - Data is often stored in flat files - rarely text, more commonly binary. Again, these are almost always completely bespoke formats. Sometimes they are aggregated into archive files which use the zip format or something similar however. Occasionally, some programs might use sqlite, and online games often use SQL databases.
3 -There are many game engines used, although the definition of 'common' is vague. There are well-known ones like the Unreal or Source engines, down to lesser known ones like Panda3D or Torque. Some of these are heavily focused on 3D and leave much of the rest of the functionality to other packages (or the game developer themselves). Most are able to be used with scripting languages, or come with one built-in. (eg. UnrealScript).
4 - J2ME - couldn't say, that's not the sector I work in.
5 - 3D web will be interesting when it's ready, but cutting edge games currently require gigabytes of client-side data. Running the application in the browser doesn't get around that download, so it's not a great benefit. Nor is it likely to be as high performing as a dedicated 3D game renderer for quite some time. So while it opens many doors, it doesn't significantly change the state of play for gaming just yet.
6 - 3D art assets are usually made with 3D Studio Max or Maya, although there are several other related tools.
7 - MMORPG networking firstly requires understanding of basic networking (ie. strip away all the HTTP fluff and get right down to the socket level). Start with Beej, work up. From there, you're best off reading talks given at conferences and reading the Massively Multiplayer Game Development books, coupling that with anything you can find on traditional game networking. 2 good starting points are the Source Multiplayer Networking docs, and Gaffer's Networking for Games Programmers. Don't expect to understand everything the first time you read it, either. And bear in mind this is a field with ongoing research and the problems are far from solved yet. And that it's also a field where "if you have to ask, you can't do it yet". Emphasis on yet.
8 - I don't know what you mean by game flow - it's not a term I've heard used before.
9 - There are several physics libraries available, including Havok, ODE, Bullet, PhysX, Box2D, etc. Some are free, some are not. You can also write your own physics for simple games, as it's not all that hard, and indeed that is what everybody did until relatively recently.
10 - Real time cutscenes are typically either pre-animated in something like 3D Studio Max, or scripted to run within the game engine.
It depends very much on the platform you are developing for. some game engines, or platforms, have built in platform specific means of creating UI systems. An example is developing for the 360 where there is a proprietary UI system provided with the SDK tools.
However, systems like these tie you to a particular platform and this can be undesirable.
Another alternative is cross platform libraries like Scaleform, which provide game-side libraries for displaying UI elements, and a common way of editing and creating UI systems across different platforms.
The complexity of UIs in videogames varies wildly. Look at something like Peggle, compared to something like Codemaster's Dirt or EA's Dead Space. Each system is therefore implemented differently.
Some use 3D packages and the standard game engine to animate and render UIs. Others implement Flash. Others roll their own custom solutions. There's no easy choice or a standard like CSS I'm afraid!
Hope this helps,
-Tom
Closed. This question is off-topic. It is not currently accepting answers.
Want to improve this question? Update the question so it's on-topic for Stack Overflow.
Closed 10 years ago.
Improve this question
I've got a young nephew who aspires to grow up to be a game programmer and i'd like to introduce him to the world of open-source as well as get him a sweet gift.
Anything like that out there?
Well, this is a tricky question because we don't know the level your nephew is at, nevermind the fact that it's difficult to produce a very nice showy game without a lot more work than a beginner might put forth.
X Game Station
Nevertheless, André LaMothe's X Game Station is meant to be exactly the system you're asking for - a beginner's guide and system on how to develop complex programs with interactive elements and gameplay on resource limited hardware. Which is pretty much what a game designer is called on to do.
GP32
The GP32 was also meant to fill this gap, but with a much more powerful processor. The successor was never released, and the company went bankrupt shortly after, but you may still be able to find one on ebay or within the communities that developed around the original machine.
Google Android
You might also consider looking toward the Google Android platform. Cell phone gaming is now and will be one of the biggest platforms in the future. The android isn't set up perfectly for gaming, but it's a good first approximation, isn't horribly expensive and includes a robust development toolset for a high-end mobile processor. Several big name game development companies have already pledged support for this platform, so it will also look good on a resume.
But a cheap computer and a VGA graphics book is surprisingly fun as a kid...
-Adam
There are a number of Open Source platforms out their for game development, if you go to here there are a large number of game engines and development platforms. For a beginner with little programming experience I would suggest a game engine like Game Maker or RPG Maker, which are drag and drop game engines. Both of these are free open source game engines. The other problem with these two game engines is that they are limited to 2D games only, even though Game Maker allows you to make and FPS that is like Doom style graphics.
For a more intermediate or beginning programmer I would honestly suggest Torque, which has both a 2D and 3D game engine. This engine is licensed as open source, but you still have to pay for the compiled version from their site. I have had much success with Torque in the past, especially Torque Game Builder (2D Game Engine). It is very simple to pickup and begin making good looking/functional games. In fact, a number of XBOX live games have been built using Torque game engines, like Marble Blast.
Another open source game engine I have heard good things about, but have not had a chance to try, is Multiverse. Multiverse is actually aimed at MMOG creation. The nice thing about Multiverse is that it provides for the creation of a 3D game environment, but also allows for the integration of Flash content into the game world.
For a more advanced programmer I would suggest looking into the SDL, OpenGL, and OpenAL. These are not game engines but graphics and sound libraries for game programmers. These are completely open source and are free to use. Most game technologies will have some implementation of one or all of these libraries in their software.
Even though XNA is not open source, it is also a good place to start for more advanced programmers. Not only does it allow for the creation of XBOX games, but you can also develop for the PC and Zune also.
Another thing you may want to suggest to your nephew is to modify existing games he owns. Most PC games and many console games allow for game modification of some form or another (level design, rescripting, etc). Some of the more popular game engines that I have seen mods for are the Source Engine and Unreal Engine. There are a number of tutorials at MODDB and 3DBuzz (which also has great tutorials on other aspects of game programming and design).
In addition to what I have listed, I have also heard good things about Ogre3D and Havok (a physics engine used in many many games). He can also go to such sites as IGDA, Gamasutra, GameDev,Game Career Guie, 3D Buzz for additional information on game development.
Hope this information helps.
I saw a question earlier about programming on a Nintendo DS. That sounds like it might be what you're looking for.
Also, I recently read about the BUG which looks like a really cool platform for building any number of handheld devices.
You might be interested in the XGameStation. It's a hardware console designed to teach programming a game console. It was created by Andre LaMothe who has written several books on game programming.
http://devmaster.net/devdb/engines/sylphis-3d#general-overview looks pretty nice, c/c++ oriented, GPL license, and Free.
I'd third the Nintendo DS recommendation - grab a R4 "homebrew" cartridge and you're pretty much set.
Another idea is one of the independent handhelds - something like the GP32, though there's certainly newer devices on the market.
I believe this is somewhat like Basketball, start from close to the basket and work your way out and you'll be hitting 3's with practice.
In my opinion, game programming is 3pt, without learning to shoot the basketball properly, you will probably cheat and start slinging it or just chucking the ball at the backboard hoping it's going to go in.
If you have a youngster without the ability to shoot a mid-range basket properly, do you think he will be able to motivate himself to keep trying, rather then trying something closer to the goal and working himself outside when he is confident?
If your nephew is serious about learning programming, get him a python book or vb.net/c# book. Maybe he will become more interested in application development because of these languages (it was the case with me, I'm 14). :)
Edit: This is assuming he doesn't have much programming experience.
well, this is not completely open source (the editor isn't, the engine is), but I recommend RPG Maker VX (if he likes role playing games):
http://tkool.jp/products/rpgvx/eng/index.html
I have used this (and the earlier versions) for some time. It is nice because there is a great editor and event system which can teach basic programming concepts without writing any code. Once your nephew wants to write some real code, there is an entire API (RGSS2) written in ruby that they he is free to manipulate and extend. This API makes up most of the game engine, hiding only low level implementation stuff.
There are other programs out there like GameMaker, but RPG Maker is the most user friendly, while still providing a way to get at the more advanced stuff.
EDIT: I forgot to mention one of the best parts; there is a large and active community around RPG Maker. There are many forums completely dedicated to the program where people will be happy to help on even the most basic tasks, not to mention the great resources that are avilable.
Well programming on the NintendoDS is possible, however you'll be breaking and stretching quite a few laws there.
However, I should say that I learned most of what I did about hardware doing stuff just like that while I was back in school. I learned a LOT from doing that sort of stuff ;)
But I wouldn't recommend it to youngsters or newcomers because you'll be totally out of support (lots of frustration), might break your game console, and unless you already know about programming the learning curve is WAY to high.
Might I recommend starting out with flash or PC games before console programming?
Edit: When I mean breaking/stretching laws, I don't mean writing code for your hardware, that's up to you. But it is illegal to buy pirate memory cards and card writers (that infringe on patent laws). Also funding hardware piracy will unlikely be something to proud of.
Edit:#Mike F did you read my post? I said, I HAVE done this while I was a student, and I learned a lot. But it's still piracy, and yes I did my fair share of piracy when I was a poor student, but it's not something I'd want to teach someone just getting into programming. Would you?
Besides there are plenty of perfectly great ways to learn game programming without needing to hack stuff like RPGMaker, XNA, etc...
#Mike F: Once more just for the sake of it NDS flash-roms are produced through patent piracy(/infringement), not software piracy, as in it is illegal to produce such hardware because it goes against patent laws. And the companies that make such flash rom hardware are piracy companies that traffic their goods in the grey market, Its as simple as that. I'm not talking about "software piracy" at all here. Thats why I mentioned twice already that anyone is free to run whatever software on their hardware, be homebrew or whatever.
Ars Technica just came out w/ an article about open-source gaming consoles. They are hand-helds, so I don't know if that's an issue but they seem to be pretty nice, with lots of features to tinker with.