Robocode/FAQ

Frequently asked questions about Robocode.

Installing and using

I can't install Robocode.

First make sure you have Java installed on your computer. To check it, run the command: java -version It should execute and show a version 1.5 or higher. If not, go to Sun site and download the last version. After, make sure you have downloaded the correct file (robocode-setup-X.X.X.jar, where X.X.X is the version number). Execute the file by double-clicking on it, or if you want to do it manually, execute the following command: java -jar robocode-setup-X.X.X.jar. It will launch an installer that will install Robocode. The installer creates the icons to execute Robocode, but you can execute it manually by running the robocode.bat or robocode.sh file in the /robocode directory.

I have downloaded a robot from the Web, but I don't know how to use it, because it doesn't appear anywhere.

By default, robots are read from the /robocode/robots directory. You can select "Robot -> Import Downloaded Robot" to copy a robot JAR to this directory from another location. Also, you can configure Robocode to read robots from additional locations using the Properties dialog.

What do I have to do to see the source code of a robot?

You can do two things. The first option is to open the Editor Window in Robocode and use the command in the File menu. The second option is to open the robot ".jar" file with a zip utility and find the source code there (assuming, of course, the robot is open source).

Can I play Robocode online?

Robocode is not an "online" game, so you can't, for example, share a battle with your friends in real time over the Internet. But you can upload your bots into the Robocode Repository and join any of the existing competitions (or organize one with your friends).

I have seen that many bots are packaged into ".jar" files. How do I package my bot?

Select, "Robot --> Package robot for upload" from the menu, then enter your robot's details when prompted.

When I test my bots, Robocode is slow. Is there a way to execute the battles faster?

When you are testing your robot, you want to execute many battles in a short time. Minimize the Robocode main screen to make it execute the battles at full speed.

Game physics

Can I fire bullets with power higher than 3.0 or lower than 1.0?

No and yes. You can't fire bullets with power greater than 3.0, but you can fire bullets with power as low as 0.1. If you call a firing function (i.e. setFire()) with a value greater than 3.0, Robocode will adjust it to 3.0, and if you call it with a power lower than 0.1 it will adjust it to 0.1.

How fast does a bullet travel?

A bullet travels at a speed between 11.0 and 19.7 depending on the power. The more powerful the bullet, the slower. The formula to calculate it is velocity = 20 - (3 * power).

Does the robot velocity get added to the bullet velocity on firing?

No, bullet velocity is not affected by robot velocity. It's kind of like the speed-of-light thing. =)

Which is the range of a bullet?

A bullet has no range. It keeps going until it hits a robot or a wall.

I want to fire a bullet every turn, but I can't. Why?

Every time you fire, the gun generates some heat. You must wait till it is cool again to fire. If you give a fire order when your gun is hot, it will do nothing. The heat generated by a shot is 1 + (firepower / 5). The gun cools down at a default rate of 0.1 per turn (note that you can change this parameter when you run the battle, but nobody usually does). It means you can fire a bullet every 16 ticks.

How much damage does a bullet do?

How do I gain or lose energy?

You lose energy every time you hit a wall, you are hit by an enemy bullet, ram an enemy, or you fire your gun. The amount of energy you lose by being hit is 4 * bullet power + 2 * max(bullet power - 1 , 0). So the maximum amount is 16.0. When you fire, you spend a quantity of energy equal to the power of the bullet fired. When one of your bullets hits an enemy, you collect back 3 * bullet power energy. When you hit an enemy bot, each bot takes 0.6 damage. If an AdvancedRobot (but not a Robot or JuniorRobot) hits a wall, it will take max(abs(velocity) * 0.5 - 1, 0) damage.

Some times I get disabled. What happens?

You can't kill yourself, so when your energy drops to zero because you hit a wall or you fire, your bot gets disabled. It will not be able to move nor fire. If you are lucky enough and one of your bullets in the air hits an enemy, you will get some energy back and recover from disabled status.

I get disabled, but I my energy > 0. Why?

You may have called a getXXX() - for example getVelocity() - function too many times a turn. The limit is 10000 getXXX() function calls per turn. To avoid disabling in such situations, store returned values in variables for future use. Another case in which you can get disabled is throwing an exception. Sometimes this will disable your bot, even if you catch the exception.

How fast do I move?

You can move at a maximum speed of 8.0 units/tick. You can modify (down) your maximum velocity by using setMaxVelocity(...). Note that your bot will always accelerate to reach it's maximum velocity.

How fast do I accelerate?

You accelerate at 1 unit/tick, and you decelerate at 2 units/tick. For example, if you are moving at an speed of 8.0 and reverse your direction your velocities will be [6.0, 4.0, 2.0, 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0].

How fast do I turn?

The faster you go, the slower you turn. The formula to calculate it in degrees is 10 - 0.75 * abs(velocity).

What is the size of a bot?

The size of a bot is 36x36. It is modeled as a non rotating square, so it's always the same regardless of its heading.

It seems that Robocode doesn't follow standard physics. If my velocity is 0 and I accelerate (acceleration = 1) my final velocity is 1, but it should be 0.5. What happened?

Time in Robocode, rather than being continuous, is in discrete "ticks". First acceleration is calculated, then velocity, and then position. So if you are stopped at a position 0 and you accelerate 1, your velocity next turn will be 1 and your position also 1.

How can I detect when an enemy has fired?

There is no direct way to detect when an enemy fired, but you can deduce it by monitoring the enemy energy drop. A drop between 0.1 and 3 usually means that it fired a bullet (there can be other reasons, such as a low energy bullet hit or a wall hit). Wall hits are (more or less) detectable as well. A deceleration > 2 means the bot hit a wall (or another bot). A deceleration <= 2 may be simple a bot hitting the brakes, or hitting a wall at velocity = 2, but since hitting a wall at that speed won't cause any damage, you can ignore that. AdvancedRobots take abs(velocity) / 2 - 1 (Never < 0) damage when hitting a wall, so by detecting (significant) wall-hits and adjusting the enemy drop accordingly, wall hits can be filtered out most of the time. This method fails when the enemy hits another robot.

How can I detect the position and heading of an enemy bullet?

You can't. There is no way to know it, directly or indirectly. But of course, you can always guess...

How fast can I turn my gun?

The gun turns at 20 degrees per tick.

How fast can I turn my radar?

It turns 45 degrees per tick.

Can I know the heading of the enemy gun/radar?

No.

Can I specify the initial position of my bot?

No. The bots are randomly placed in the field at the beginning of each round.

See Also

• Robocode Game Physics
• System Requirements for Robocode
• How to download and install Robocode
• Getting started with Robocode
• The anatomy of a robot
• My First Robot Tutorial
• Package your Robot
• List of articles about Robocode
• Scoring in Robocode
• Starting Robocode from the command line
• List of articles about Robocode