Updated 29-Jul-2021 by Flemming N. Larsen
Robocode is a programming game where the goal is to code a robot battle tank to compete against other robots in a battle arena. So the name Robocode is short for "Robot code". The player is the programmer of the robot, who will have no direct influence on the game. Instead, the player must write the AI of the robot telling it how to behave and react to events occurring in the battle arena. Battles are running in real-time and on-screen.
The motto of Robocode is: Build the best, destroy the rest!
Beside being a programming game, Robocode is used for learning how to program primarily in the Java language, but other languages like Kotlin and Scala is possible as well.
Schools and universities are using Robocode as part of teaching how to program, but also for studying artificial intelligence (AI). The concept of Robocode is easy to understand, and a fun way to learn how to program.
Robocode offers a complete development environment and comes with an installer, built-in robot editor and Java compiler.
Robocode only requires that a JRE (Java Runtime Environment) exist already on the system where Robocode is installed.
Hence, everything a Robocode developer (Robocoder) needs to get started is provided with the main Robocode distribution
file (robocode-xxx-setup.jar). Robocode also supports developing robots using external IDEs like e.g.
An external IDE aids the developer much better than the build-in robot editor in Robocode, which is just meant for making quick small fixes.
The fact that Robocode runs on the Java platform makes it possible to run it on most operating systems supporting Java, meaning that it will be able to run on Windows, Linux, macOS, and other UNIX variants. Note that Java 8 is the minimum version required by Robocode, but you can use newer versions for running Robocode and when developing bots. See the System Requirements for more information.
Be aware that many users of Robocode (aka Robocoders) find Robocode to be very fun, but also very addictive. :-)
Robocode comes free of charge and is being developed as a leisure project where no money is involved. The developers of Robocode are developing on Robocode because they think it is fun to do.
Robocode is an Open Source project, which means that all sources are open to everybody.
Robocode is provided under the terms of EPL (Eclipse Public License).
The Robocode game was originally started by Mathew A. Nelson as a personal endeavour in late 2000 and became a professional one when he brought it to his job at IBM, in the form of an AlphaWorks download, in July 2001.
IBM was interested in Robocode, as they saw an opportunity to promote Robocode as a fun way to get started with learning how to program in Java, and IBM wanted to promote Java as well.
The inspiration for creating Robocode came from Robot Battle, a programming game written by Brad Schick in 1994. Robot Battle was, in turn, inspired by RobotWar, an Apple II+ game from the early 1980s.
Articles from IBM ("Rock 'em, sock 'em Robocode", "Robocode Rumble", and "Secrets from the Robocode masters"), and the Robocode community behind the RoboWiki made Robocode very popular as a programming game, and for many years Robocode has been used for education and research at schools and universities all over the world.
At the beginning of 2005, Mathew convinced IBM to release Robocode as Open Source on SourceForge. At this point, the development of Robocode had somewhat stopped. The community around Robocode began to develop their own versions of Robocode with bug fixes and new features, e.g. the "Contributions for Open Source Robocode" and later on the two projects, RobocodeNG and Robocode 2006, by Flemming N. Larsen.
Eventually, Flemming took over for Mathew on the Robocode project at SourceForge as administrator and developer in July 2006 to continue development on the original Robocode game. Hence, the RobocodeNG project was dropped, and Robocode 2006 was merged into the new official Robocode version 1.1 of the game containing lots of improvements. Since then, lots of new versions of Robocode have been released with more and more features and contributions from the community.
In May 2007, the RoboRumble client got built into Robocode. RoboRumble is widely used by the Robocode community for creating up-to-date robot ranking lists for the 1-vs-1, Melee, Team, and Twin Dual competitions.
In 2012, the Robocode called Julian ("Skilgannon") created LiteRumble, which is intended to be a lightweight, easily deployable RoboRumble system designed to run on the Google App Engine.
In May 2010 a .Net plugin was provided for Robocode using a .NET / Java bridge that made it possible to develop robots for the .Net Framework version 3.5 beside developing robots in Java. This feature was provided by Pavel Savara, who is a major Robocode contributor.
In April 2021 the .Net plugin was discontinued as the .Net Framework and the required toolchain for building both the plugin, and the documentation files for it had got some serious issues that made it very difficult to build and maintain.
To run Robocode, Java 8 or a newer version must be installed on your system. Both the Java Runtime Environment (JRE) and the Java Developer Kit (JDK) can be used. Note that the JRE does not include the standard Java compiler (javac) which comes with the JDK. However, Robocode comes with a built-in compiler ECJ (Eclipse Compiler for Java). Hence, it is sufficient to run Robocode with the JRE only.
Also, note that it is important that these environment variables have been set up before running Robocode:
JAVA_HOME must be set up to point at the home directory for Java
(JDK or JRE).
Windows example: JAVA_HOME=C:\Program Files\AdoptOpenJDK\jdk-16.0.0.36-hotspot
Linux and macOS example: JAVA_HOME=/usr/lib/jvm/adoptopenjdk-16-hotspot-amd64
PATH must include the path to the bin of the Java home
directory (JAVA_HOME) that includes the java executable for starting the Java Virtual Machine (JVM).
Windows example: PATH=%PATH%;%JAVA_HOME%
Linux, macOS example: PATH=${PATH}:${JAVA_HOME}/bin
You can read more details from here:
Most documentation about Robocode is provided thru the RoboWiki which is hosted by Julian ("Skilgannon"). The RoboWiki is an amazing source of information about Robocode development used by most Robocoders, and it also contains lots of official documentation for Robocode.
It is recommended to read the articles on the RoboWiki for getting started with Robocode. The first article to start with is provided here:
Make sure to should read about the anatomy of a robot, the game physics, scoring etc.
The Robocode API is provided here:
The Robocode API consists of several APIs.
Robot API: Within the Java package robocode.
The Robot API is used for developing robots and is the only part of the API that robots are allowed to access.
Robot Interfaces: Within the Java package robocode.robotinterfaces.
The Robot Interfaces are used for developing new robot types with a different API than the standard Robot API.
Note: The game rules and robot behaviours cannot be changed.
Control API: Within the Java package robocode.control.
The Control API is used for letting another application startup battles with selected robots in Robocode and retrieve
the results. It is also possible to get snapshots of robots and bullets (like position, heading, energy level etc.) at
a specific time in a battle.
If you want to try out new robots other than the sample robots that come with Robocode, you should visit the LiteRumble home that contains lots of bots.
The community around Robocode is using the RoboWiki as a communication channel. At the RoboWiki, people share new ideas, code snippets, algorithms, strategies, and lots of other stuff about Robocode. New official documentation from the developers of Robocode will be put at the RoboWiki as well.
On the RoboWiki, these strategies are provided:
The code snippets are also provided on the RoboWiki:
You can also get in touch with other Robocoders on:
A good way to improve yourself as a robot developer is to try out some real challenges. On the RoboWiki, two famous challenges exist for testing/studying a robot´s movement, targeting, and gun abilities:
But there is a lot of other challenges available on RoboWiki besides the ones listed here.
If you want to challenge your robot(s) and yourself as Robocoder, the LiteRumble is the best way to do it. LiteRumble is the ultimate collaborative effort to have a live, up-to-date ranking of Robocode bots.
So don't hesitate to enter the RoboRumble competition.
It is possible to specify options and predefined properties from the command-line when running Robocode. The usage of these can be listed by writing this from a command prompt or shell:
robocode -help
For example, it is possible to:
You can read more details here:
If you discover an issue with Robocode you are encouraged to report it as soon as you discover it. The sooner the better.
A bug report should be reported on the Bugs page on the SourceForge site for Robocode. Each bug report will be prioritized among other bug reports depending on its impact on the game.
It will be a great help if you describe the necessary steps to make to reproduce the issue. You are very welcome to provide a screenshot, source code or anything else that will show the bug. It is also a very good idea to write which OS and version of both Robocode and Java you are using.
If you are a registered user at SourceForge (register here you will be able to add a "monitor" to your bug report. This way you will be able to receive notifications when someone adds comments to your report, but will also be able to better track the current status of the bug, e.g. when the bug is fixed and with which version of Robocode the fix is available.
If you are a developer yourself and have a good idea of how the bug can be fixed, you are more than welcome to do so by providing a pull request at GitHub. By fixing the bug, you will become a contributor to Robocode yourself. You can learn more about how to contribute here. Note that we accept bug fixes under the terms of EPL.
If you got an idea for a new feature or improvement for Robocode, you are very welcome to share your idea by summiting a feature request or start a discussion on the Robocode Application Developers group.
A feature request should be put on the Feature Requests on the SourceForge site for Robocode. Each feature request will be prioritized among other feature requests.
Note that if the feature is a big change to the game, e.g. change the robot behaviour, it might not be accepted, as Robocode is being used for competitions like e.g. the LiteRumble.
It will be a great help if you describe your idea in detail, and how you think it could be implemented into Robocode. For example, will it be possible to extend an existing feature with your idea?
If you are a registered user at SourceForge (register here you will be able to add a "monitor" to your request. This way you will be able to receive notifications when someone adds comments to your request entry, but will also be able to better track the current status of your entry, e.g. when the feature has been implemented and with which version of Robocode it will be available.
If you are a developer yourself and have a good idea of how the feature could be implemented, you are more than welcome to do so if the feature is being accepted. By implementing the feature, you will become a contributor to Robocode yourself. You can learn more about how to contribute here. Note that we accept implementations under the terms of EPL.
News about Robocode is put on the blog spot for Robocode. Here it is possible to subscribe to an RSS feed to receive news about Robocode.
You can also follow Robocode on Twitter and Facebook here:
The RoboWiki can be followed on Twitter as well:
If you want to contribute to Robocode with e.g. a new feature or bug fix, you should start by reading the Developers Guide for building Robocode.
Note that we accept code changes under the terms of EPL.
There exist no or little documentation about the internals of Robocode, and the codebase will need to be examined as a contributor to get an insight into how Robocode is implemented. Thus, it required a skilled Java developer to figure out how Robocode is put together.
Robocode is divided into several modules. You can read Pavel Savara's blog post to get a good overview of Robocode here:
Help for Robocode internals can be provided through the Robocode Application Developers where you can register yourself, and start up a new topic. This is the best way of getting information and asking about details for the internals in Robocode.
If a contribution is a somewhat small change to involves under 10 files, then the preferred way is to do a pull request at GitHub.
Your pull request will be reviewed and tested out before being accepted and merged into Robocode. Also, note that additional work might be done by other Robocode developers to finalize the work or make some adjustments.