Core War - The King of Programming Games

The aim of a programming game is to write a short program that competes towards a goal, usually destroying all opponents or capturing a flag.

There are two main types of programming game:

• games inspired by RobotWar - programs control a battle robot which moves around an arena firing at opponents – RobotWar was created in the 1970s.
• games inspired by Darwin - programs attempt to modify and crash the opponent's program. Darwin was first played at Bell Labs in 1961.

Both games have spawned a series of clones, the most popular being CRobots (1985) and Core War (1984).

In Core War players write programs in Redcode, the assembly language of the MARS virtual computer. The aim of the game is to survive while causing all opponents to terminate. There are three basic strategies:

• paper - programs spawn off new copies in the hope at least one survives.
• scissors - programs search for opponents and attempt to disable them.
• stone - programs drops instructions at random hoping to hit the opponent.

A couple of years after A. K. Dewdney introduced Core War a society was formed which organised an annual tournament. The First International Core War Tournament held in the Computer Museum, Boston MA was a great success with a paper coming out on top, Mice by Chip Wendell.

Core War is now played as a King of the Hill tournament. Players submit their program to a hill containing some of the top Core War programs, receiving results a few minutes later. If the program is successful it enters the hill, knocking off the lowest warrior.

Despite being 26 years old Core War still has a community of regular players. Although the major techniques appear to have been discovered new ideas are constantly being tested, occasionally with impressive results. If you’d like to find out more about Core War here are some handy links for new players:

• The Beginner’s Guide to Redcode
• Core War Strategy Guides
• Core War King of the Hill
• Koenigstuhl Core War Archive
• The Core War Bibliography

If you’re planning to try your hand at writing a battle program, good luck and may the core be with you!

A History of Programming Games 1961-1989

In a programming game players write a program to complete a specific task, usually to wipe out all opponents. The contest takes place between either programs in the memory of a virtual computer or robots in an arena.

Darwin

In August 1961, Douglas McIlroy, Robert Morris and Victor Vyssotsky invented Darwin and the programming game genre. Programs written using IBM 7090 machine code competed to destroy all opponents and be the most prolific replicator. An Umpire provided three functions to probe memory for an opponent, to claim memory or kill an opponent.

RobotWar

RobotWar was written in the 1970s by Silas Warner for the PLATO computer system and published commercially for the Apple II by MUSE Software in 1981. Programs written in a proprietary high level language control robots which battle to eliminate all opponents in a virtual arena. In the early 1980s a society was formed and an annual tournament organised by Computer Gaming World.

Color Robot Battle

The Image Producers released Color Robot Battle in 1981 for the TRS-80 Color Computer. The game was played by writing programs in a simple hybrid of BASIC and Logo to control a battle robot. Programs faced each other in a one-on-one battle with the last robot standing being declared winner.

Core War

Alexander Dewdney described Core War in the May 1984 issue of Scientific American, introducing programming games to a wide audience for the first time. Core War became popular overnight. A society was formed, a newsletter published and regular tournaments held. Core War is played between assembly languages programs in the memory of a virtual computer. Each program attempts to eradicate all opponents. Core War can be played by email at KOTH.org or KOTH@SAL.

DROID

Inspired by RobotWar, DROID was developed at Reichhold Chemicals as a teaching aid in December 1984. Programs to control robots are written in the D-code assembly language and attempt to exterminate all adversaries in the virtual arena. DROID can be played by Telnet on the Empire HPe3000 server.

CROBOTS

Tom Poindexter published CROBOTS as shareware in December 1985 after being inspired by RobotWar. A subset of C is used to control battle robots. As usual, the aim of the game is to destroy all opponents in a virtual arena. A king of the hill tournament is organised by Maurizio Camangi.

P-Robots

In 1988 David Malmberg released P-Robots, a robot battle game based on a subset of the Pascal programming language and inspired by CROBOTS. Later versions introduced a variety of optional extras for robots, teams and obstacles.

OMEGA

OMEGA is a programming game written by Stuart Marks and published by Origin Systems in 1989. The object of the game is to program a tank to defeat a series of increasingly more powerful enemies. Each opponent defeated unlocks a higher security clearance and increased budget.

Unfortunately there's very little information about some of these games online. Do you remember playing any of the above? Which is your favourite programming game and why?

CoreLife: Programming in 2 Dimensions!

For a while I've been promising to take a closer look at Dennis Luehring's list of programming games to select a few for further investigation. The list contains over 1500 links in 200 categories!

The first I've chosen is CoreLife, a 2D variant of Corewar by Brent Adams. CoreLife is one of the earliest 2D programming languages, predating Befunge by a few months.

Battles take place on a 100 × 100 memory grid. The outcome of a battle isn't uniquely determined by the initial conditions as there's a random element to the game.

Unfortunately, there's very little information about CoreLife strategies. There are 13 published battle programs. Most of these launch imps or bomb the grid with protected locations. Battle programs are often surrounded by a membrane or shield of protected locations. Despite this CoreLife has the potential to support more complex programs, for example replicators.

I've set myself the challenge of writing a replicator. First I'll attempt to write something linear and if that's successful, a square replicator! Has anyone experimented with CoreLife and if so, did you create a successful program or discover anything interesting?

For more information about programming games, take a look at Steven Robbins' list of programming games or Dennis Luehring's list of programming games.

Core War - Hostile Programming

Core War is a game from the 80's, played between computer programs written in Redcode, a language similar to assembly.  The programmers design their battle programs to remove opponents from the memory of the MARS virtual computer by any means possible.

Some of the simpler techniques include blindly overwriting memory, searching for the opponent or spawning off new processes. These are commonly known as stone, scissors, paper after the popular playground game.  Stone usually wins against scissors, scissors normally defeat paper, and paper mostly beats stone.

Here's an example of a typical Core War program:

org   wipe

step  equ 5
first equ bomb-10

bomb:mov.i #1,       -1

ptr: sub   #step,    #first
wipe:jmz.f ptr,      @ptr

mov   bomb,     >ptr
djn.f wipe,     {ptr-5

end

This simple example of scissors once held a 20 point lead over it's rivals. The first instruction is never executed, it's the bomb used to overwrite opponents.  The next two instructions form a loop which look through memory for an opponent, and the final two instructions actually overwrite it.

Core War is still going strong, and celebrates it's 25th anniversary in 2009. If you'd like to discover more about Core War, here are the top resources:

• The Beginner's Guide to Redcode will teach you the language of Core War
• pMARS is a portable implementation of the Core War virtual machine
• Core War Tutorials exist on virtually every aspect of the game
• Koenigstuhl is an archive of thousands of published Core War programs
• SAL organises a number of on-going king of the hill tournaments
• sfghoul and impomatic report the latest Core War news on their blogs
• #corewars is the official Core War discussion channel, hosted by irc.freenode.net

What are your experiences with Core War, have you ever had any success?