Traditional RTS games Archives

Traditional RTS games Archives

traditional RTS games Archives

traditional RTS games Archives

Whether it’s turn-based or real-time, strategy is good for the mind.

Full control is hard to come by, but thanks to the strategy genre the power to command a million worlds is right at your fingertips. Every game’s universe abides by different rules and you better learn them fast, because we’re about to hit you with 50 of the best indie strategy games you can get your mits on! So pull up a commander’s chair or ruler’s throne, you’re about to take the controls.

50. Panzer Strategy

Panzer Strategy takes high octane battle-based warfare into the incredibly satisfying, albeit slower, realm of strategy. Develop your own unique tactics as you command your armies and weaponised vehicles through the battles of the second world war, forever altering history as you do so. The game world is based on one of intense historical accuracy. View some of the most infamous battles through the eyes of each side, developing each strategy over the course of political meetings with your country’s leaders all the way through to deployment on the battlefield.

Each unit has been developed to reflect the real life strengths and weaknesses of their equipment, so history buffs are sure to have the upper hand here. Never touched a history book in your life? That’s fine too, there’s plenty to learn about the machines that won, and lost, the second world war. What’s more, the result of each air, sea, or land battle will influence the next, and even side missions have bearing on the final historical outcome of your game. That outcome could be anything, as well, as Panzer Strategy’s non-linear narrative means every decision you make could turn the tide in battle.

49. Taste of Power

Once you get a taste of power, you’ll need a full meal to sustain you. Thankfully for medieval RTS fans, there’s far more than just a sliver of control in OneOceanLLC’s Taste of Power. The forces of Europe, China, and the Middle East have found themselves at a deadly impasse in what developers have touted as a Starcraft meets Total War alternative Middle Ages RTS.

Play as one of three factions each with their own unique skills abilities. Europeans can use gunpowder artillery and have their monks raise moral, meanwhile the Chinese have smoke grenades ready to befuddle their opponents and evade arrows. The Middle East is made up of the Timurids, warriors able to command chariots and underground tunnels beneath enemy lines alike. All the traditional mechanics of the RTS genre are in here, build your cities, manage your troops, and send forces out to conquer unknown lands; it’s not always pretty but it makes a satisfyingly complex strategy experience.

48. Achtung! Cthulhu Tactics

How do you solve a problem like the Nazis? It’s a question video games have never shied away from asking, namely because Nazis make pretty good enemies; it’s a general requirement of decent humanity to hate them and we, therefore, don’t feel so bad about shooting them in the face. Achtung! Cthulhu Tactics gives us a new reason to raise the barrel, Nazis raising tentacle monsters with science. Developer Auroch Digital took the Achtung! Cthulu tabletop hit and digitised it into a classic real-time strategy game with a sprinkling of RPG.

While Panzer Strategy gives players an all-encompassing insight into the battlefield, Achtung! Cthulu Tactics is a decidedly more focused approach to World War 2 strategy. Development is linear and on a strict trajectory; players evolve their units with a wide breadth of skills and develop their tactics according to the new threat. The narrative of Achtung! is all the better for it, with the horror of your enemies increasing with every step and a powerful sense of dread in each move. Gather your militarised team and take on the Nazis, and whatever else they’ve got brewing, in a solid RTS experience with an impressive narrative premise.


The lands of Valtoria have been ravaged by war, starvation, and distaster. Now it’s your turn to stand up and lay claim to the kingdom, assembling your bannermen in all regions of the map and fighting your way to victory. Pathos Interactive presents a strong, if slightly canonical, real time strategy adventure in which players inhabit a fantastical world as Lord Berrian, a commander with his eyes set on the throne. As you travel through the world you’ll have to gather resources and build communities of supporters willing to follow you into battle, micro-managing each unit’s abilities and skills while maintaining wider control over the full map.

While gameplay is pretty typical of the RTS genre, unique Temples offer some relief of the tried and tested mechanics of the RTS world. Construct Temples in key areas to unlock powerful Natural Powers, skills that can be deployed for widepread destruction. Beware, though, once you erect your Temple, your opponents will be notified and can see how close you are to being able to use your new abilities. That can be especially tricky outside of the single player campaign, if you’re playing a ranked or unranked online game, for example. Bannermen is a strategy adventure done well, with a spattering of unique mechanics to keep players interested.


Defcon takes real time strategy beyond the maths of troup count and strength on the battlefield and introduces a more psychological approach. Set during the Cold War, players are tasked with obliterating enemy territories while remaining in the safe, cozy confines of their underground bunker. While there’s certainly enough battlefield action to keep traditional battle strategy players interested, the nature of the nuclear weapons you are detonating require a new level of cunning and skill. Expose your position, or play your hand too much and you’ll have hell to pay as enemy forces are able to stamp out your efforts in one fell swoop.

You’re probably thinking ‘this sounds a lot like a game about nuclear genocide’, and you’d be right. This is an in-depth, richly populated world of nuclear war and all the alliances, paranoia, and terror that come with it. Manage your units, sure, but pay closer attention to the factions supporting you in your endeavour. Never has the phrase ‘keep your friends close and your enemies closer’ been more applicable to a virtual world.

45. Game Dev Tycoon

Ever wondered what goes on behind the scenes of your favourite games? Game Dev Tycoon not only places you in the developer’s shoes, but does it on a whirlwind tour of gaming’s biggest moments in history. As you assemble a team of crack nerds and climb the review score ladder, you’ll balance your remaining funds with the benefits of research, game engine development, contract work, and releasing the blockbuster game that will get you out of your Mum’s basement.

Use your cunning knowledge of the games industry to develop the games that sell on each console, living the high life during the casual Gameboy days all the way through to the next generation of consoles and engine technology. Learn from each success and failure to hone your craft and make a name for your studio in the world of game development. It’s easy to see why Game Dev Tycoon flourished when released in XX, giving players a chance to sit in the steering wheel of their own studio is incredibly fun. Experimenting with different combinations of genre, engine, features, consoles, topics and development specialties to produce the perfect experience to get you thinking about every title you download.

44. Mini Metro

If you’re a commuter navigating the treacherous underground world of subways and tube lines, you’ll either appreciate the complexity of our modern public transport or hate it with a deep, burning passion. Chances are it’s the latter. Mini Metro gives you the chance to put your money where your mouth is, literally saying ‘if you think it’s so bad, try making it yourself’. You start the game with three stations and it’s your job to connect them all with subway lines. Easy enough, but there aren’t only three stations in the world. Think of the congestion.

As the game continues you’ll be juggling a growing city population with new transport demands in order to accommodate the hordes of stressed commuters and tourists waiting to get from A to B. Keeping all of your trains running efficiently and ensuring a successful final design is no easy task. If you find yourself struggling in the time-sensitive main game mode, you can always kick back with some good old city planning in Creative Mode, or continue your failed design in Endless Mode which alleviates some of the passenger thresholds and train capacities. Dinosaur Polo Club’s puzzle strategy experience is definitely a unique title, just don’t spend too long critiquing the tube’s layout after becoming a transportation maestro.

43. Mushroom Wars 2

The sequel to the original Mushroom Wars RTS experience, Mushroom Wars 2 brings a refreshed art style and brand new multiplayer opportunities to Zillion Whales’ forest adventure. A single player campaign sets players on a journey across over 100 missions meanwhile online and local multiplayer with ranked league tables gives you the chance to put your fungi management to the test. Build your villages, towers, and forges all while destroying those of your opponents to seal a victory in the easy to pick up, hard to master battlefield experience. There’s plenty of charm in each hero character’s abilities and the visual design of your arena, but the mechanics are also working hard to provide a rich experience under the hood.

Defeat your enemy by taking over their buildings and obliterating their forces, all while balancing your own troops’ movement and population. You’ll have to act fast, Mushroom Wars has been designed to offer a lighter but more immediately satisfying experience with a Nintendo Switch port compared to its PC RTS counterparts, so battles rarely last more than 10 minutes a go.

42. Re-Legion

In the age of wars of ideology, Re-Legion presents a recognisable narrative overlaying a complex real time strategy experience. The leader of a cyperpunk cult, your job in Re-Legion is to convert the disillusioned masses of drug addicts and alcoholics into cult members, eventually training them up to obliterate the non-believers. This dystopian world has been raised under an oppressive cyber regime, and it’s your job as the charmingly dangerous cult leader to shape your own religion, evolve your abilities, and recruit an army of dissenters.

Lead your followers into battle and watch as they gladly lay down their lives for your cause, attacking unbelievers and corporations in order to reach enemy lines and hack their way in. Re-Legion abides by classic RTS structures, but with an intriguing story underpinning the experience’s unique atmosphere and subject matter. What happens when one narcisstic idealist utilises the power of the downtrodden? That’s up to you!

41. Satellite Reign

The worlds of Satellite Reign and Re-Legion could be one and the same. Rainy cyberpunk city streets ruled under the heavy fist of mega-corporations are often the site of riotous dissent, though Satellite Reign loses the organised linearity of Re-Legion in favour of an open world of exploration and adventure. As you move through the city you’ll come up against a range of enemy forces, it’s up to you to assemble the right team and select the best strategy for the job.

All of your work to unclench the corporate grasp over this neon-lit city is fully your own. The creative freedom afforded to players in their street-level escapades singles Satellite Reign out from other items on this list. With a game world championing emergent gameplay, players can build their armies by cloning promising members of the public and selecting from a wide talent pool of mercenary rebels, take on each moment of combat in their own unique manner, and explore a world of new objectives and missions.

Next up: Public transport woes, hordes of zombies and dinosaurs

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The Best RTS Games

There are many lists of the best RTS games, and many of those lists a packed with the classics from the 90’s and early 2000’s. These legends have quite rightly earned their place in the real-time hall of fame for all time, but this status quo sees the same titles appearing time and again, with little new to say about them. It can leave newer releases in the cold.

The rise of MOBAs has challenged the RTS scene quite significantly over the past decade, but that hasn’t stopped some worthy games rising to the top ranks to earn their own place in a future generation's hall of fame.

The header image is from Battle for Middle-Earth 2. Strategy Gamer is a Affiliate.

What are the best RTS Games?

  • The Lord of the Rings: The Battle for Middle Earth (1 and 2)
  • John Wick Hex
  • Driftland: The Magic Revival
  • Bad North: Jotunn Edition
  • Shadow Tactics: Blades of the Shogun
  • Tropico 6
  • Offworld Trading Company
  • Homeworld: Deserts of Kharak
  • Company of Heroes 2: Ardennes Assault
  • Age of Empires 2
  • StarCraft 2: Wings of Liberty
  • Ashes of the Singularity: Escalation

The Lord of the Rings: The Battle for Middle-Earth (1 or 2)

Developer: EA Los Angeles
Publisher: EA

This one debuts on the list because we were thinking about it recently when Renata pointed out that, not only was it a pretty interesting RTS, but it was also one of the best Lord of the Rings digital adaptations to date. Not necessarily in terms of the core stories of the books but generally on how the developers at managed EA Los Angeles (who would go on to make Command & Conquer 3 & 4) to translate the feel of the different factions from the source material into an RTS context.

While Renata is very much in favour of the second game, plenty of readers have commented to us since that they actually preferred the first title, so we've listed both. Critically they received roughly the same score. The only caveat with this listing is that it's very hard to find a copy of the game for sale. EA lost the license in 2010 so you're stuck with trying to find second-hand discs or... 'other' means. Playing online as well is best done via services such as GameRanger, or the website which has managed to preserve the game and make it playable in solo and multiplayer.

John Wick Hex

Developer: Bithell Games
Publisher: Good Shepard Entertainment
Buy From:Epic Games Store

I know this is going to cause some controversy, but I'm having a real tough-time with this one, ok? Hear me out - My thinking is, John Wick Hex can't be a turn-based game because there's no defined set of time for the turn to play out in. You choose an action, whether it be walking, or firing your gun, and time advances however long it takes for that action to play out. Meanwhile the game still plays out around you at it's own pace regardless of what you're doing, and your action could end part-way through a enemy playing out their action. It's not like BSG Deadlock, where a fixed amount of time passes in between issuing orders. So yeah, for now until we hear otherwise John Wick Hex is an RTS games. Kind of. Don't @ Me.

Identity crises aside, this is a very inventive and addictive strategy game where you play as John Wick, from the movies, in a prequel story set before the first film. You don't actually need to know much about the films for this to work - mastering the rhythm and the dynamics of the game's 'time-line' system is fascinating enough, and there are a surprising amount of tactical options to approach any given situation. This probably one of the most decent tie-in games we've seen in a long while.

Driftland: The Magic Revival

Developer: Star Drifers
Publisher: Star Drifters
Buy, Steam

It's nice to see a new face finally make it onto this list - Driftland was in Early Access for a couple of years before it finally released in April 2019, and it seems that time has been put to good use. This is an innovative RTS that follows in the mould of the classic Majesty franchise - where indirect control is the order of the day. You are a Mage whose realm is on one of many shattered pieces of the world floating around, and you must develop your holdings and expand onto other ones by connecting them together.

It's not for everyone, and there are some other minor niggles that will need to get worked out over time, but Driftland willingness to be bold and experiment does it justice, and anyone looking for a new fantasy RTS game need look no further. Read our Driftland: The Magic Revival review for more.

Bad North: Jotunn Edition

Developer: Plausible Concept
Publisher: Raw Fury
Buy From:,Discord, Steam

Self-styling itself as a 'micro strategy' game, Bad North is the poster child for minimalist design facilitating tight tactical decision making. Evoking the best bits of games like FTL, this game sees you taking your modest force from island to island, protecting them against waves of blood-thirsty marauders. As you progress through the game you can earn coins to level up your troops, recruit new troops and find powerful items to aid you.

At the end of July 2019 Bad North got a major content update known as the Jotunn Edition. This is a huge content update, changing everything from meta progression, to adding new items, to gameplay and difficulty, and more. It's been folded into the main game and is now the 'definitive' version of Bad North. 

Shadow Tactics: Blades of the Shogun

Developer: Mimimi Productions
Publisher: Daedalic Entertainment
Buy from:, Steam, PS4

This isn't a new release but we feel it's definitely worth mentioning as Shadow Tactics is a wonderfully tense real-time tactical/puzzle game that will challenge not only your creative thinking, but also your combo and control skills. This is a stealth-based game that follows in the hallowed tradition of classics like Commandos, but also taking queues from modern contemporaries like Assassins Creed. With a very powerful and engaging narrative, you must guide up to five characters through vibrant and varied levels. Subterfuge is key, and 'fighting your way out' isn't really an option.

This is a wonderful homage to a forgotten genre of strategy games, but one that stands proud as it creates its own legacy. The attention to detail on the maps & characters makes this a story you genuinely want to experience right through the end, with characters you can 100% get behind. The tactical puzzles you are presented with map-to-map will challenge your creativity and handling of the characters to the very end – and at no point does it feel like a chore.

Tropico 6

Publisher: Kalypso Media
Developer: Limbic Entertainment
Buy, Steam

Ah, Tropico. The Banana Republic sim, the Castro sim, the tin-pot dictator sim. Tropico 6 represents a clean slate in the series' history - originally under the helm of Surviving Mars studio Haemimont, (who were responsible for Tropico's 3-6), Limbic Entertainment have now taken over control of everyone's favourite dictatorship. This is a refreshing twist on the city builder that puts players in the aviators and oversized cigars of not just one, but an entire dynasty of male and female despot wannabes. Starting in the twilight of the Imperial era, the player’s role is that of the manager of a new colony on a Caribbean isle, who eventually earns their independence and then proceeds to navigate the literal and political waters of the World Wars, the Cold War, and into the modern era, with the player choosing such roles as either a socialist dictator, or crony capitalist.

Tropico 6 is a great game. It hits many of the right notes, and has that “just a little longer” feel that will keep you in its sandbox (and coming back) for quite a while. It’s an easy pick for fans of sim games. And of course, there’s always the benefit that you can lord over the lives of hundreds of virtual people with as iron or velvet a hand as you desire – and that’s always a good time!

Offworld Trading Company

Publisher: Stardock
Developer: Mohawk Games
Buy, Direct

Offworld Trading Company is an object lesson in RTS design. It’s a competitive strategy game in which there is no actual direct combat. And no units. Inspired by classic Atari game MULE and systems like Age of Empires’ Marketplace interface, Offworld Trading Company has players compete by cultivating the economic portfolio of an ambitious, hostile company.

Players are tasked with choosing which resource(s) to harvest to produce income which they can use to, ultimately, buy out their opponent's companies one by one. To this end they are aided by intermittent auctions, the ability to freely buy and sell any resource in the game as well as attack their opponent's production with Pirates, EMPs, nuclear warheads or temporary takeovers of their operations. Ultimately, OTC is a game of efficiency, coupled with prediction and daring. It is, in every sense, the essence of what RTS games are about laid bare for all to see.

Homeworld: Deserts of Kharak

Publisher: Gearbox Software
Developer: Blackbird Interactive
Buy From:,Steam

A new take on the classic series’ mechanics and a prequel to the original Homeworld, Deserts of Kharak is beautiful, haunting, powerful and intense. While I was initially sceptical of how the “six degrees of freedom” RTS would pan out on a flat plane, Blackbird Interactive has packed Deserts of Kharak with nuance and heart. One of the best RTS solo campaigns in history, coupled with gameplay that hides surprising subtlety, Homeworld: Deserts of Kharak has been sadly overlooked by the larger RTS community.

Company of Heroes 2: Ardennes Assault

Publisher: SEGA
Developer: Relic Entertainment
Buy From: Steam

With the advent of the Western Front Armies, the overhauling of its War Spoils system and years of balance refinement, Company of Heroes 2 has cemented its place as a respectable and enjoyable competitive strategy game. With the creation of the Ardennes Assault campaign, Company of Heroes 2 has now also earned the honour possessing one of the best replayable single player experiences in modern real-time strategy gaming.

Ardennes Assault provides players with a strategic territory-capture metagame layered over the single-player missions, including semi-random events and time-based objectives that change with each playthrough, four Companies to command (of which you can utilize three in each campaign playthrough) and hard choices in an Iron Man setting. These force the player to think through each move and live with sub-optimal strategies across the length of the campaign. Where the Soviet storyline in the core game was seen as sub-par or at the very least not supremely creative, Ardennes Assault is a well-crafted take on RTS single player.

Age of Empires 2 (2013)

Publisher: Microsoft Game Studios
Developer: Hidden Path Entertainment
Buy From: Steam

I feel like I’m cheating, sneaking an older game into this article; while Age of Empires 2's first HD remake came out in 2013, the original was released in 1999. Age of Empires 2 HD was a testament to the enduring quality of classic RTS games. Also of note, three expansions (The Forgotten, The African Kingdoms, Rise of the Rajas) have been released, something kind of unprecedented in the real-time strategy space as far as I know.

The depth and complexity of this classic Age of Empires title is reaching, enchanting, challenging, and captivating the imaginations of a new generation of strategy gamers, and was perhaps the inspiration for Microsoft announcing remakes of virtually every other Age title ever made. It's worth noting that in November 2019 Age of Empires 2: Definitive Editionwas released that largely supersedes the 2013HD release, even though you can buy both separately. It's essentially the same game with even better graphics and a new expansion pack. We've not updated this entry fully because the 2013 edition had far more impact on the RTS genre than the newest versionThat said, there's no point buying the HD version if you don't already own it - go straight to the DE.

StarCraft 2: Wings of Liberty

Publisher: Blizzard
Developer: Blizzard
Buy From:Direct

You knew this was coming. You might have nodded grudgingly, or groaned inwardly. There’s nothing so contentious as the enduring popularity of StarCraft. It’s common to blame the ‘esports-ification’ of the genre on this phenomenally popular strategy game. But, love it or hate it, you can’t deny that StarCraft has continually set the standards for game polish and features for almost a decade now.

Through relentless balancing, aggressive additions of content, engaging unit designs (yes yes we all hate the Sentry, but that’s the exception not the rule), and a multiplayer scene that virtually every other strategy game is jealous of, StarCraft 2 has rightly earned it its place at the top of the competitive strategy world. Co-op was an absolute coup, and I actually had a sobering day mourning RTS developers everywhere when they announced that SC2 was going to be free-to-play for multiplayer and arcade.

Ashes of the Singularity: Escalation

Publisher: Stardock
Developer: Oxide Games
Buy From:,Direct

While it is undeniable that Ashes of the Singularity launched in a pretty weird place, with a somewhat characterless campaign and what felt like a dearth of unit options, it’s matured in a big way via a long cycle of continued development and optimisation. It now stands as one of the more interesting takes on large-scale RTS that exists in the modern time.

Ashes of the Singularity takes nods from Total Annihilation-style games, but also from Company of Heroes with its squad-based light vehicles, and interconnected resource nodes which function similarly in many respects to territories from Relic’s seminal World War 2 RTS. It uses structure-based support powers similar to those found in Command and Conquer 3, and constrains player upgrades and unit counts through the scarce Quanta resource (which is also used to activate support powers). The campaign DLC has vastly improved in quality, and while the game’s specifications make it difficult to run on all but higher-end machines, Ashes is shaping up to be a serious contender in the large-scale RTS space.

Other RTS Game Recommendations

The below games featured on our list in the past, but have since rotated out to join their brothers and sisters in the hall of heroes:

What would your list of top RTS games look like? Let us know in the comments!


Related Posts from Strategy Gamer

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traditional RTS games Archives

A Multiagent Potential Field-Based Bot for Real-Time Strategy Games


Bots for real-time strategy (RTS) games may be very challenging to implement. A bot controls a number of units that will have to navigate in a partially unknown environment, while at the same time avoid each other, search for enemies, and coordinate attacks to fight them down. Potential fields are a technique originating from the area of robotics where it is used in controlling the navigation of robots in dynamic environments. Although attempts have been made to transfer the technology to the gaming sector, assumed problems with efficiency and high costs for implementation have made the industry reluctant to adopt it. We present a multiagent potential field-based bot architecture that is evaluated in two different real-time strategy game settings and compare them, both in terms of performance, and in terms of softer attributes such as configurability with other state-of-the-art solutions. We show that the solution is a highly configurable bot that can match the performance standards of traditional RTS bots. Furthermore, we show that our approach deals with Fog of War (imperfect information about the opponent units) surprisingly well. We also show that a multiagent potential field-based bot is highly competitive in a resource gathering scenario.

1. Introduction

A real-time strategy (RTS) game is a game in which the players use resource gathering, base building, technological development and unit control in order to defeat its opponent(s), typically in some kind of war setting. The RTS game is not turn-based in contrast to board games such as Risk and Diplomacy. Instead, all decisions by all players have to be made in real time. Generally the player has a top-down perspective on the battlefield although some 3D RTS games allow different camera angles. The real-time aspect makes the RTS genre suitable for multiplayer games since it allows players to interact with the game independently of each other and does not let them wait for someone else to finish a turn.

In RTS games computer bots often “cheats,” that is, they have complete visibility (perfect information) of the whole game world. The purpose is to have as much information available as possible for the artificial intillegence (AI) to reason about tactics and strategies in a certain environment. Cheating is, according to Nareyek, “very annoying for the player if discovered” and he predicts the game AIs to get a larger share of the processing power in the future which in turn may open up for the possibility to use more sophisticated AIs [1]. The human player in most modern RTS games does not have this luxury, instead the player only has visibility of the area populated by the own units, and the rest of the game world is unknown until it gets explored. This property of incomplete information is usually referred to as Fog of War or FoW.

In 1985, Ossama Khatib introduced a new concept while he was looking for a real-time obstacle avoidance approach for manipulators and mobile robots. The technique which he called Artificial Potential Fields moves a manipulator in a field of forces. The position to be reached is an attractive pole for the end effector (e.g., a robot) and obstacles are repulsive surfaces for the manipulator parts [2]. Later on Arkin [3] updated the knowledge by creating another technique using superposition of spatial vector fields in order to generate behaviors in his so called motor schema concept.

Many studies concerning potential fields are related to spatial navigation and obstacle avoidance (see, e.g., [4, 5]). The technique is really helpful for the avoidance of simple obstacles even though they are numerous. Combined with an autonomous navigation approach, the result is even better, being able to surpass highly complicated obstacles [6].

Lately some other interesting applications for potential fields have been presented. The use of potential fields in architectures of multi agent systems is giving quite good results defining the way of how the agents interact. Howard et al. developed a mobile sensor network deployment using potential fields [7], and potential fields have been used in robot soccer [8, 9]. Thurau et al. [10] have developed a game bot which learns reactive behaviours (or potential fields) for actions in the first-Person Shooter game Quake II through imitation.

The article is organised as follows. First, we propose a methodology for multiagent potential field- (MAPFs-) based solution in an RTS game environment. We will show how the methodology can be used to create a bot for a resource gathering scenario (Section 4) followed by a more complex tankbattle scenario in Section 5. We will also present some preliminary results on how to deal with imperfect information, Fog of War (Section 6). The methodology has been presented in our previous papers [11, 12]. This article summarises the previous work and extends it by adding new experiments and new results. Last in this article, we have a discussion and line out some directions for future work.

2. A Methodology for Multiagent Potential Fields

When constructing a multiagent potential field-based system for controlling agents in a certain domain, there are a number of issues that we must take into consideration. It is, for example, important that each interesting object in the game world generates some type of field, and we must decide which objects can use static fields to decrease computation time.

To structure this, we identify six phases in the design of an MAPF-based solution: (1)the identification of objects;(2)the identification of the driving forces (i.e., the fields) of the game;(3)the process of assigning charges to the objects;(4)the granularity of time and space in the environment;(5)the agents of the system;(6)the architecture of the MAS.

In the first phase, we may ask us the following questions. What are the static objects of the environment? That is, what objects keep their attributes throughout the lifetime of the scenario? What are the dynamic objects of the environment? Here we may identify a number of different ways that objects may change. They may move around, if the environment has a notion of physical space. They may change their attractive (or repulsive) impact on the agents. What is the modifiability of the objects? Some objects may be consumed, created, or changed by the agents.

In the second phase, we identify the driving forces of the game at a rather abstract level, for example, to avoid obstacles, or to base the movements on what the opponent does. This leads us to a number of fields. The main reason to enable multiple fields is that it is very easy to isolate certain aspects of the computation of the potentials if we are able to filter out a certain aspect of the overall potential, for example, the repulsive forces generated by the terrain in a physical environment. We may also dynamically weight fields separately, for example, in order to decrease the importance of the navigation field when a robot stands still in a surveillance mission (and only moves its camera). We may also have strategic fields telling the agents in what direction their next goal is, or tactical fields coordinating the movements with those of the teammate agents.

The third phase includes placing the objects in the different fields. Static objects should typically be in the field of navigation. The potentials of such a field are precalculated in order to save precious run time CPU resources.

In the fourth phase, we have to decide the resolution of space and time. Resolution of space means how detailed the navigation in the game world should be. Should for example the agents be able to move to every single point in the world, or should the game world be divided into a grid with tiles of for example points in the world? Resolution of time means how often the potential fields should be updated. If the agents are able to move around in the environment, both these measures have an impact on the lookahead. The space resolution obviously, since it decides what points in space that we are able to access, and the time in that it determines how far we may get in one time frame (before it is time to make the next decision about what to do).

The fifth phase is to decide what objects to agentify and set the repertoire of those agents: what actions are we going to evaluate in the lookahead? As an example, if the agent is omnidirectional in its movements, we may not want to evaluate all possible points that the agent may move to, but rather try to filter out the most promising ones by using some heuristic, or use some representable sample.

In the sixth step, we design the architecture of the MAS. Here we take the unit agents identified in the fifth phase, give them roles, and add the supplementary agents (possibly) needed for coordination, and special missions (not covered by the unit agents themselves).


Open real-time strategy (ORTS) [13] is a real-time strategy game engine developed as a tool for researchers within artificial intelligence (AI) in general and game AI in particular. ORTS uses a client-server architecture with a game server and players connected as clients. Each timeframe clients receives a data structure from the server containing the current game state. Clients can then call commands that activate and control their units. Commands can be like “move unit A to or attack opponent unit X with unit A.” The game server executes the client commands in random order.

Users can define different types of games in scripts where units, structures, and their interactions are described. All types of games from resource gathering to full real-time strategy (RTS) games are supported.

We will begin by looking at a one-player resource gathering scenario game called Collaborative Pathfinding, which was part of the 2007 and 2008 ORTS competitions [13]. In this game, the player has 20 worker units. The goal is to use the workers to mine resources from nearby mineral patches and return them to a base. A worker must be adjacent to a mineral object to mine, and to a base to return resources. As many resources as possible will be collected within 10 minutes.

This is followed by looking at the two-player games, Tankbattle, which was part of the 2007 and 2008 ORTS competitions [13] as well.

In Tankbattle, each player has 50 tanks and five bases. The goal is to destroy the bases of the opponent. Tanks are heavy units with long fire range and devastating firepower but a long cool-down period, that is, the time after an attack before the unit is ready to attack again. Bases can take a lot of damage before they are destroyed, but they have no defence mechanism of their own so it may be important to defend our own bases with tanks. The map in a tankbattle game has randomly generated terrain with passable lowland and impassable cliffs.

Both games contain a number of neutral units (sheep). These are small indestructible units moving randomly around the map. The purpose of sheep is to make pathfinding and collision detection more complex.

4. Multiagent Potential Fields in ORTS

First we will describe a bot playing the Collaborative Pathfinding game based on MAPF following the proposed methodology. Collaborative Pathfinding is a 1-player game where the player has one control center and 20 worker units. The aim is to move workers to mineral patches, mine up to 10 resources (the maximum load a worker can carry), then return to a friendly control center to drop them off.

4.1. Identifying Objects

We identify the following objects in our application: Cliffs, Sheep, Base stations, and workers.

4.2. Identifying Fields

We identified five tasks in ORTS: avoid colliding with the terrain, avoid getting stuck at other moving objects, avoid colliding with the bases, move to the bases to leave resources, and move to the mineral patches to get new resources. This leads us to three major types of potential fields: a field of navigation, a strategic field, and a tactical field.

The field of navigation is a field generated by repelling static terrain. This is because we would like the agents to avoid getting too close to objects where they may get stuck, but instead smoothly pass around them.

The strategic field is a dynamic attracting field. It makes agents go towards the mineral patches to mine, and return to the base to drop off resources.

Own workers, bases, and sheep generate small repelling fields. The purpose of these fields is the same as for obstacle avoidance; we would like our agents to avoid colliding with each other and bases as well as avoiding the sheep. This task is managed by the tactical field.

4.3. Assigning Charges

Each worker, base, sheep, and cliffs has a set of charges which generates a potential field around the object. These fields are weighted and summed together to form a total potential field that is used by our agents for navigation.

Cliffs, for example, impassable terrain, generate a repelling field for obstacle avoidance. The field is constructed by copying pregenerated matrixes of potentials into the field of navigation when a new game is started. The potential all cliffs generate in a point is calculated as the lowest potential a cliff generates in that point. The potential in a point at distance from the closest impassable terrain tile is calculated as:

Own worker units generate repelling fields for obstacle avoidance. The potential at distance from the center of another worker is calculated as

Sheep. Sheep generate a small repelling field for obstacle avoidance. The potential at distance from the center of a sheep is calculated as

Own Bases. The own bases generate two different fields depending on the current state of a worker. The base generates an attractive field if the worker needs to move to the base and drop off its resources. Once it has arrived at the base, all the resources are dropped. The potential at distance from the center of the base is calculated as

In all other states of the worker, the own base generates a repelling field for obstacle avoidance. Below is the function for calculating the potential at distance from the center of the base. Note that this is, of course, the view of the worker. The base will effect some of the workers with the attracting field while at the same time effect the rest with a repelling field. If a point is inside the quadratic area the base occupies, the potential in those points is always 10000 (potential used for impassable points):

Minerals, similar to own bases, generate attractive fields for all workers that do not carry maximum loads and a repelling field for obstacle avoidance when they do. The potential of the attractive field is the same as the attractive field around the own base in (4).

In the case when minerals generate a repelling field, the potential at distance from the center of a mineral is calculated as

4.4. The Granularity of the System

Since the application is rather simple, we use full resolution of both the map and the time frames without any problems.

4.5. The Agents

The main units of our system are the workers. They use a simple finite state machine (FSM) illustrated in Figure 1 to decide what state they are in (and thus what fields to activate). No central control or explicit coordination is needed, since the coordination is emerging through the use of the charges.

4.6. The Multiagent System Architecture

In addition to the worker agents, we have one additional agent that is the interface between the workers and the game server. It receives server information about the positions of all objects and workers which it distributes to the worker agents. They then decide what to do, and submit their proposed actions to the interface agent which in turn sends them through to the ORTS server.

4.7. Experiments, Resource Gathering

Table 1 shows the result from the Collaborative Pathfinding game in 2008 years' ORTS tournament. It shows that an MAPF-based bot can compete with A*-based solutions in a resource gathering scenario. There are however some uncertainties in these results. Our bot has disconnected from the server (i.e., crashed) in 30 games. The reason for this is not yet clear and must be investigated in more detail. Another issue is that Uofa has used the same bot that they used in the 2007 years' tournament, and the bot had a lower score this year. The reason, according to the authors, was “probably caused by a pathfinding bug we introduced” [14]. Still we believe that with some more tuning and bug fixing our bot can probably match the best bots in this scenario.

TeamMatchesAvg. ResourcesDisconnected


5. MAPF in ORTS, Tankbattle

In the 2-player Tankbattle game, each player has a number of tanks and bases, and the goal is to destroy the opponent bases. In [11] we describe the implementation of an ORTS bot playing Tankbattle based on MAPF following the proposed methodology. This bot was further improved in [12] where a number of weaknesses of the original bot were addressed. We will now, just as in the case of the Collaborative pathfinding scenario, present the six steps of the used methodology. However, there are details in the implementation of several of these steps that we have improved and shown the effect of in experiments. We will therefore, to improve the flow of the presentation, not present all of them in chronologic order. Instead we start by presenting the ones that we have kept untouched through the series of experiments.

5.1. Identifying Objects

We identify the following objects in our application: Cliffs, Sheep, and own (and opponent) tanks and base stations.

5.2. Identifying Fields

We identified four tasks in ORTS: Avoid colliding with the terrain, Avoid getting stuck at other moving objects, Hunt down the enemy's forces, and Defend the bases. In the resource gathering scenario we used the two major types: field of navigation and strategic field. Here we add a new major type of potential field: the defensive field.

The field of navigation is, as in the previous example of Collaborative pathfinding, a field generated by repelling static terrain for obstacle avoidance.

The strategic field is an attracting field. It makes units go towards the opponents and place themselves on appropriate distances where they can fight the enemies.

The defensive field is a repelling field. The purpose is to make own agents retreat from enemy tanks when they are in cooldown phase. After an agent has attacked an enemy unit or base, it has a cooldown period when it cannot attack and it is therefore a good idea to stay outside enemy fire range while being in this phase. The defensive field is an improvement to deal with a weakness found in the original bot [11].

Own units, own bases, and sheep generate small repelling fields. The purpose is the same as for obstacle avoidance; we would like our agents to avoid colliding with each other or bases as well as avoiding the sheep. This is managed by the tactical field.

5.3. Assigning Charges

The upper picture in Figure 2 shows part of the map during a tankbattle game. The screenshots are from the 2D GUI available in the ORTS server. It shows our agents (light-grey circles) moving in to attack an opponent unit (white circle). The area also has some cliffs (black areas) and three sheep (small dark-grey circles). The lower picture shows the total potential field in the same area. Dark areas have low potential and light areas have high potential. The light ring around the opponent unit, located at maximum shooting distance of our tanks, is the distance from which our agents prefer to attack opponent units. The picture also shows the small repelling fields generated by our own agents and the sheep.



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