The following was published in the February 2010 issue of Game Developer magazine…

Who decides what a game is about?

At first glance, the popular board game Ticket to Ride seems to be another link in the great chain of rail baron games, such as Age of Steam, Eurorails and the 1830 series. During the game, the player draws unique route challenges, to connect certain pairs of cities – New York to San Francisco, Miami to Chicago, and so on.

To complete them, she must claim a series of tracks that connect adjacent cities while also trying to block her opponents from finishing their own challenges. There are sub goals too, such as having the longest contiguous rail line and completing one’s network first, which ends the game for everyone.

Thus, most players would describe Ticket to Ride as a game about building the best rail service, by grabbing choice routes and cutting off the competition. However, the introduction in the rules tells a different story:

On a blustery autumn evening five old friends met in the backroom of one of the city’s oldest and most private clubs. Each had traveled a long distance – from all corners of the world – to meet on this very specific day… October 2, 1900 – 28 years to the day that the London eccentric, Phileas Fogg, accepted and then won a £20,000 bet that he could travel Around the World in 80 Days.

Each succeeding year, they met to celebrate the anniversary and pay tribute to Fogg. And each year a new expedition (always more difficult) was proposed. Now at the dawn of the century it was time for a new impossible journey. The stakes: $1 Million in a winner-takes-all competition. The objective: to see which of them could travel by rail to the most cities in North America – in just 7 days.

The official story comes as a surprise to many players, even veterans of the game, because the theme simply does not match the gameplay. For example, how can a player “claim” a route just by riding on it? Do the trains shut down, preventing anyone else from using that line? On the other hand, claiming routes matches perfectly the fiction of ruthless rail barons trying to control the best connections.

Furthermore, routes can be claimed in any order – there is no sense that the player actually exists in the world as a traveler with real, physical limitation. Instead, claiming routes feels a lot more like buying them rather than traveling on them.

Mechanics Give Meaning

This disconnect leads to some interesting questions. Does a game’s designer have the right to say what a game is about if it doesn’t match what’s going on inside the players’ heads? And if the designer doesn’t have this right, then does a game’s official “story” ever matter at all because it can be invalidated so easily? Isn’t a game about what one actually does during play and how that feels to the player?

Ultimately, designers need to recognize that a game’s theme does not determine its meaning. Instead, meaning emerges from a game’s mechanics – the set of decisions and consequences unique to each one. What does a game ask of the player? What does it punish, and what does it reward? What strategies and styles does the game encourage? Answering these questions reveals what a game is actually about.

Furthermore, while people buy games for the promise of the theme (“I want to be a space marine!”), the fun comes from the mechanics themselves (actually shooting the aliens). When there is a severe dissonance between the two, players can feel cheated, as if the designers executed a bait-and-switch.

The reception of Spore, a game sold with an evolutionary theme, provides a recent example. In the October 2008 issue of Science magazine, John Bohannon wrote the following about how the game delivered on the theme’s promise:

I’ve been playing Spore with a team of scientists, grading the game on each of its scientific themes. When it comes to biology, and particularly evolution, Spore failed miserably. According to the scientists, the problem isn’t just that Spore dumbs down the science or gets a few things wrong–it’s meant to be a game, after all–but rather, it gets most of biology badly, needlessly, and often bizarrely wrong.

The source of this dissonance is that, even though it was sold as such, Spore is not really a game about evolution. Spore is actually a game about creativity – the reason to play the game was to behold the wonder of other players’ imaginations as they used (and misused) the editors to create objects not imagined by the game’s designers – from musical instruments to fantastical creatures to dramatic scenes.

However, even though Spore is not about evolution, the scientists should keep looking because one of the most popular games actually is about evolution – World of Warcraft. The game may have a swords-and-sorcery theme, but the mechanics encourage the players to conduct their own form of natural selection when deciding how to develop their characters.

Over years of experience, veterans of WoW have established a number of upgrade paths (or “builds”) for each class, depending on what role the player wants the character to fill. For example, the Paladin class has three main builds: Holy (for healing), Protection (for tanking), and Retribution (for damage-per-second). Further, underneath these main categories, sub-builds exist for player-vs-player, player-vs-environment, and mob grinding. These paths have evolved organically over the years as players tried out different combinations, depending on what the game rewarded or punished.

Seeing Past the Theme

One can look at any number of games through the lens of how the mechanics affect the user experience to find out what the game actually means. Super Mario Bros., for example, is a game about timing, certainly not about plumbing. Battlefield games are about teamwork, not World War II or modern combat. Peggle is a game about chaos theory, not unicorns or rainbows.

Indeed, games with the same theme can actually be about different things. For example, human conflict with aliens has certainly been a popular theme across video game history. Nonetheless, each alien-themed game can mean something very different depending on the rule set. Galaga is actually about pattern matching. X-Com is about decision-making with limited information. Gears of War is about using cover as a defensive weapon. StarCraft is about the challenges of asymmetrical combat.

Conversely, games with different themes but the same mechanics are actually about the same thing. Civilization and Alpha Centauri are set on completely different planets, but the mechanics are largely the same. Alpha Centauri’s mind worms, probe teams, and Secret Projects are essentially identical to Civilization’s barbarians, spies, and World Wonders. Players can easily see past the game’s chrome to see that they are still making the same decisions with the same tradeoffs.

Genre choice can also affect the meaning of a game. Players expect a theme to deliver on certain nouns and verbs. (“I am a Mage – I can cast powerful Magic!”) Unfortunately, genre conventions often put a barrier between a player and the game he imagined while holding a copy in the store. Once again, players buy games for the theme – if the mechanics and traditions of the genre are wildly unfamiliar to the player, at odds with the game in his head, he may feel cheated.

For example, two recent console games – Halo Wars and Brutal Legend – surprised players by being strategy games. With the former, many players expected a Halo game to be about reflex-based combat; with the latter, heavy-metal music is not inherently strategic. Because strategy games are often played at a considered distance, players expecting the visceral thrill promised by the games’ themes were disappointed. The designers may have built fun and interesting rule sets, but the themes sold the games to the wrong fans.

Uniting Theme and Mechanics

One interesting comparison is the board games Risk and Diplomacy, which have identical themes of world conquest. Indeed, at first glance, the two games also seem quite similar mechanically. The game board is split up into territories, which the players control with generic army or (in the case of Diplomacy) navy tokens. These territories switch hands as battles are fought, and – in turn – the victors are able to field larger militaries from their new lands.

However, a small difference in the rules makes the two games about something very different. In Risk, turns occur sequentially while, in Diplomacy, they execute simultaneously. This difference makes Risk a game about risk while Diplomacy becomes a game about diplomacy. In the former, players must decide how much they can achieve during their own turn and then hope the dice are not unkind. With Diplomacy, however, there are no dice; players can only succeed with the help of others, which can only be promised but not actually delivered during the negotiation round. Only when the secretly-written orders are revealed between turns is it clear who is a true friend and who is a backstabbing traitor.

Diplomacy, in particular, is a perfect marriage between theme and mechanics. Indeed, President John F. Kennedy considered it his favorite game. The game is about exactly what it claims to be about – the twists and turns of diplomatic negotiations. On the other hand, when a game’s theme and mechanics are sharply divorced, players can react negatively to the dissonance. Part II shall discuss examples of games which made a successful union of the two and ones which did not – and the rewards and costs of doing so.

The following was published in the December 2009 issue of Game Developer magazine…

The surgery game Trauma Center was one of the earliest examples of how the Nintendo DS could change our industry. By turning the stylus into a scalpel, the designers let players immerse themselves into the role of a doctor as never before. Unfortunately, the game simulated the pressures of actual surgery as well by presenting staggeringly difficult, time-pressured levels.

Failure blocked the player’s progress, which proved to be a fatal flaw for the game because there were no difficulty levels at all – no way for the player to decide what level of challenge was appropriate. Considering the wide demographic of gamers today, from young children to seniors, this decision doomed the game to a tiny slice of the DS’s audience.

Challenge has always been a core component of game design. However, after video games left the arcades – in which quick difficulty ramps were a necessity of doing business – most designers realized that their games could appeal to more people if they tailored the challenge to meet the needs of the individual user.

Dynamic Difficulty

Call of Duty 4, for example, measures the player’s performance during the training level to suggest an appropriate difficulty level. Other games – such as Left 4 Dead – have developed dynamic difficulty algorithms which adjust enemy spawns and health drops to the player’s current situation and demonstrated skill.

However, dynamic difficulty can be a tricky proposition as – similarly to AI cheating – if the player can see the invisible hand controlling the challenge, the spell is broken. Players need to perceive that they are improving against a fixed measuring stick. The RPG Oblivion turned off many people by scaling the weapons and skills of enemies directly in relation to the player character’s level.

Once this mechanic became obvious, many absurd strategies emerged, such as never leveling up to ensure that enemies always stayed weak. More significantly, this dynamic ruined one of the core features of an RPG – power progression. After developing advanced characters, players enjoy easily brushing aside monsters which earlier in the game could have destroyed them.

Elective Difficulty

Indeed, the core mechanic of RPG’s – that the player character grows slowly in power after each successful battle – can be seen as a way to give players the ability to adjust the game’s difficulty themselves. Gamers who feel comfortable with the combat system can push ahead through levels at the edge of their abilities while players who prefer a more comfortable experience can grind their way to overpowered characters before proceeding. Most importantly, this system puts the player in control, not the designer.

Although selecting a difficulty level at start was a simple, early innovation, only recently have games allowed players to switch between them during normal play. On every third death in Ninja Gaiden Black, players could elect to drop to “Ninja Dog” mode, which weakened enemies but also forced Ryu to wear pink ribbons as punishment. This mechanic – minus the mockery – was quickly adopted by other games, such as God of War.

Indeed, elective difficulty itself can be a core gameplay mechanic. The browser-based Desktop Tower Defense has no difficulty levels at all but does allow the player to speed up the game (and thereby increase the challenge) by triggering attack waves prematurely. Then, the final score is calculated from not just how many enemies were destroyed but also from how quickly the game finished. Therefore, beating DTD on the default speed is just the beginning as players must learn how to master the speed-up mechanic to start improving their scores.

Orthogonal Challenges

While the difficulty levels of Thief do not determine the number of guards nor their awareness on a given level, they do specify the challenges the player sets for herself during the level. For instance, the requirements of Easy may only be stealing a certain number of jewels and artifacts while Hard also necessitates finishing the level without killing a single guard.

These different modes suggest orthogonal challenges within the same game, a smart way to extend a game’s life for the hard-core. Other official examples include the One City Challenge and Always War options in Civilization 4 and the Hardcore mode (with permanent death) in Diablo 2. Indeed, Xbox Live Achievements provide a fantastic infrastructure for adding new challenges via unorthodox goals to games that might otherwise no longer interest core gamers.

Furthermore, other settings can adjust the challenge of a game without changing the difficulty, per se. For example, a real-time strategy game could have both a difficulty setting and a speed setting, so a player could try a more difficult AI but at a slower speed if he did not enjoy time pressure. One sadly forgotten setting is the complexity option that appeared in earlier games, such as M.U.L.E. and Lords of Conquest. This option provided a simpler version of the game – with less types of resources, for example – but still with a fully-capable AI that could provide a challenge for new players.

Challenge and Punishment

However, some games choose to punish players on top of giving them a fair challenge. Games without generous save systems, for instance, are vulnerable to being ruined by challenging sub-sections, which might require multiple attempts to pass. If a player needs to repeat a lengthy but easy section (or, more shamefully, a non-skippable cut-scene) before getting to the difficult bit, the game is punishing the player instead of challenging him.

One of the most elegant solutions to this problem was the time control mechanic in Prince of Persia: Sand of Time, in which the player is able to rewind past mistakes a limited number of times to try again. This system reduced the overhead of repeating a difficult jump to a relative minimum while still retaining tension because of the finite number of rewinds.

Another example of reducing punishment can be seen in the history of MMO’s. World of Warcraft famously reduced the penalty for death found in its predecessors, such as Everquest and Ultima Online. By removing corpse runs and experience loss, WoW enabled people to play the game they way they wanted to play it. Instead of only attacking easy monsters which would never cause the loss of experience or loot, players could attempt a difficult battle knowing that, in the worst case, they would be warped back to a safe location.

Thus, games with severe penalties for failure can actually warp the core gameplay by strongly encouraging players to always choose the safe route. Defense of the Ancient, the popular mod for Warcraft 3, rewards the opposite team with gold every time a player is killed, which makes bumbling new players extremely unpopular with their teammates. This simple dynamic makes the DotA community notoriously nasty and unpleasant, even by the meager standards of the Internet.

After Punishment

The strategy/puzzle hybrid Puzzle Quest took WoW‘s forgiving nature to the logical extreme by removing all forms of punishment from the game entirely. Players are even rewarded for losing battles, albeit much less than they would be for winning them. In fact, this mechanic has an interesting side benefit; Puzzle Quest has no need for a visible save system. Because players are never penalized in any way, the game can comfortably auto-save after every battle or action, knowing that a player will never feel the need to revert to an earlier save.

Such a forgiving system is not for every game. Bioshock used a similar mechanic by respawning dead players for free in Vita-Chambers placed throughout the game. Furthermore, enemies health rates were not reset on a player respawn, which meant that the player could chip away at any enemy with any weapon, including the wrench, if she was willing to die and be reborn enough times. This feature felt like an exploit to enough players that Irrational eventually patched in an option to disable Vita-Chambers.

However, the problem may have been with the expectations of Bioshock‘s intended audience instead of any fundamental flaw with the respawn mechanic. Lego Star Wars uses an identical mechanic, which is perfect for the target audience of a dad and a son playing together in a forgiving environment. For Bioshock, core gamers expected the game to force them to use advanced strategies to progress instead of an easy out.

Perhaps the best solution is to always allow players to progress but to rate their performance against some constant metric. Elite Beat Agents hands out letter grades of S, A, B, C, and D for each song performance based on the player’s timing. The game continues as long as the player finishes the song, but few will not want to go back to try and improve. If Trauma Center had only adopted such a simple system, the game may have become more than just an interesting footnote. Designers should take care not to head down the same dead-end.

The following was published in the October 2009 issue of Game Developer magazine…

One of the most powerful tools a designer can use when developing games is probability, using random chance to determine the outcome of player actions or to build the environment in which play occurs. The use of luck, however, is not without its pitfalls, and designers should be aware of the trade-offs involved – what chance can add to the experience and when it can be counterproductive.

Failing at Probability

One challenge with using randomness is that humans are notoriously poor at accurately evaluating probability. A common example is the Gambler’s Fallacy, which is the belief that odds will even out over time. If the Roulette wheel comes up black five times in a row, players often believe that the odds of coming up black again are quite small, even though clearly the streak makes no difference whatsoever. Conversely, people also see streaks where none actually exist – the shooter with a ‘hot hand’ in basketball, for example, is a myth. Studies show that, if anything, a successful shot actually predicts a subsequent miss.

Also, as designers of slot machines and MMO’s are quite aware, setting odds unevenly between each progressive reward level makes players think that the game is more generous than it really is. One commercial slot machine had its payout odds published by wizardofodds.com in 2008:

• 1:1 per 8 plays
• 2:1 per 600 plays
• 5:1 per 33 plays
• 20:1 per 2,320 plays
• 80:1 per 219 plays
• 150:1 per 6,241 plays

The 80:1 payoff is common enough to give players the thrill of beating the odds for a a big win but still rare enough that the casino is in no risk of losing money. Furthermore, humans have a hard time estimating extreme odds – a 1% chance is anticipated too often and 99% odds are considered to be as safe as 100%.

Leveling the Field

These difficulties in accurately estimating odds actually work in the favor of the game designer. Simple game design systems, such as the dice-based resource generation system in Settlers of Catan, can be tantalizingly difficult to master with a dash of probability.

In fact, luck makes a game more accessible because it shrinks the gap – whether in perception or in reality – between experts and novices. In a game with a strong luck element, beginners believe that, no matter what, they have a chance to win. Few people would be willing to play a chess Grandmaster, but playing a backgammon expert is much more appealing – a few lucky throws can give anyone a chance.

In the words of designer Dani Bunten, “Although most players hate the idea of random events that will destroy their nice safe predictable strategies, nothing keeps a game alive like a wrench in the works. Do not allow players to decide this issue. They don’t know it but we’re offering them an excuse for when they lose (‘It was that damn random event that did me in!’) and an opportunity to ‘beat the odds’ when they win.”

Thus, luck serves as a social lubricant – the alcohol of gaming, so to speak – that increases the appeal of multiplayer gaming to audiences which would not normally be suited for cutthroat head-to-head competition.

Where Luck Fails

Nonetheless, randomness is not appropriate for all situations or even all games. The ‘nasty surprise’ mechanic is never a good idea. If a crate provides ammo and other bonuses when opened but explodes 1% of the time, the player has no chance to learn the probabilities in a safe manner. If the explosion occurs early enough, the player will immediately stop opening crates. If it happens much later, the player will feel unprepared and cheated.

Also, when randomness becomes just noise, the luck simply detracts from the player’s understanding of the game. If a die roll is made every time a StarCraft Marine shoots at a target, the rate of fire will simply appear uneven. Over time, the effect of luck on the game’s outcome will be negligible, but the player will have a harder time grasping how strong a Marine’s attack actually is with all the extra random noise.

Further, luck can slow down a game unnecessarily. The board games History of the World and Small World have a very similar conquest mechanic, except that the former uses dice and the latter does not (until the final attack). Making a die roll with each attack causes a History of the World turn to last at least three or four times as long as a turn in Small World. The reason is not just the logistical issues of rolling so many dice – knowing that the results of one’s decisions are completely predictable allows one to plan out all the steps at once without worrying about contingencies. Often, handling contingencies are a core part of the game design, but game speed is an important factor too, so designers should be sure that the trade-off is worthwhile.

Finally, luck is very inappropriate for calculations to determine victory. Unlucky rolls feel the fairest the longer players are given to react to them before the game’s end. Thus, the earlier luck plays a role, the better for the perception of game balance. Many classic card games – pinochle, bridge, hearts – follow a standard model of an initial random distribution of cards that establishes the game’s ‘terrain’ followed by a luck-free series of tricks which determines the winners and losers.

Probability is Content

Indeed, the idea that randomness can provide an initial challenge to be overcome plays an important role in many classic games, from simple games like Minesweeper to deeper ones like NetHack and Age of Empires. At their core, solitaire and Diablo are not so different – both present a randomly-generated environment that the player needs to navigate intelligently for success.

An interesting recent use of randomness was Spelunky, which is indie developer Derek Yu’s combination of the random level generation of NetHack with the game mechanics of 2D platformers like Lode Runner. The addictiveness of the game comes from the unlimited number of new caverns to explore, but frustration can emerge from the wild difficulty of certain, unplanned combinations of monsters and tunnels.

In fact, pure randomness can be an untamed beast, creating game dynamics that throw an otherwise solid design out of balance. For example, Civilization 3 introduced the concept of strategic resources which were required to construct certain units – Chariots need Horses, Tanks need Oil, and so on. These resources were sprinkled randomly across the world, which inevitably led to large continents with only one cluster of Iron controlled by a single AI opponent. Complaints of being unable to field armies for lack of resources were common among the community.

For Civilization 4, the problem was solved by adding a minimum amount of space between certain important resources, so that two sources of Iron could never be within seven tiles of each other. The result was a still unpredictable arrangement of resources around the globe but without the clustering that could doom an unfortunate player. On the other hand, the game actively encouraged clustering for less important luxury resources – Incense, Gems, Spices – to promote interesting trade dynamics.

Showing the Odds

Ultimately, when considering the role of probability, designers need to ask themselves ‘how is luck helping or hurting the game?’ Is randomness keeping the players pleasantly off-balance so that they can’t solve the game trivially? Or is it making the experience frustratingly unpredictable so that players are not invested in their decisions?

One factor which helps ensure the former is making the probability as explicit as possible. The strategy game Armageddon Empires based combat on a few simple die rolls and then showed the dice directly on-screen. Allowing the players to peer into the game’s calculations increases their comfort level with the mechanics, which makes chance a tool for the player instead of a mystery.

Similarly, with Civilization 4, we introduced a help mode which showed the exact probability of success in combat, which drastically increased player satisfaction with the underlying mechanics. Because humans have such a hard time estimating probability accurately, helping them make a smart decision can improve the experience immensely.

Some deck-building card games, such as Magic: The Gathering or Dominion, put probability in the foreground by centering the game experience on the likelihood of drawing cards in the player’s carefully constructed deck. These games are won by players who understand the proper ratio of rares to commons, knowing that each card will be drawn exactly once each time through the deck. This concept can be extended to other games of chance by providing, for example, a virtual “deck of dice” that ensures the distribution of die rolls is exactly even.

Another interesting – and perhaps underused – idea from the distant past of gaming history is the “Element of Chance” game option from the turn-based strategy game Lords of Conquest. The three options available – Low, Medium, and High – determined whether luck was only used to break ties or to play a larger role in resolving combat. The appropriate role of chance in a game is ultimately a subjective question, and giving players the ability to adjust the knobs themselves can open up the game to a larger audience with a greater variety of tastes.

The following was published in the August 2009 issue of Game Developer magazine…

One of the most important choices a designer makes at the start of a project is deciding whether to make a turn-based game or a real-time one. Each type of base game mechanic provides potential benefits and drawbacks. While turn-based games favor more strategic and transparent play, they can feel a little stodgy to players used to action-oriented titles. Real-time games, on the other hand, are more immersive and multiplayer-friendly but can also easily overwhelm new players if they are not well-paced.

Turn-based games, of course, descend directly from the board game tradition which predates video games. Indeed, the fanbase for turn-based games still overlaps significantly with the fanbase for board and card games. Real-time games (excluding sports) were only truly possible with the advent of computers. Indeed, quite a few games – Super Mario Bros., Team Fortress, FIFA, Pac-Man – could only ever conceivably be developed as real-time games.

However, quite a few games could go either way, with an understanding that each path comes with its own set of trade-offs. Roguelike dungeon-crawlers, for example, have been made as both turn-based and real-time games. Early versions, such as NetHack, were purely turn-based; the game’s clock only moves forward each time the player takes an action. However, Blizzard’s Diablo put the same explore-and-loot formula into a real-time environment and created an experience that was less strategic but more visceral and potentially addictive. Furthermore, without the waiting inherent in a turn-based system, the designers could develop a viable multiplayer mode.

Nonetheless, Diablo has not surplanted the continuing popularity of turn-based roguelikes, such as Pokemon Mystery Dungeon or Shiren the Wanderer, which maintain their own tactical charm. Thus, deciding between turn-based and real-time is not a question of which system is “better” or “worse” but rather a question of which set of trade-offs best fits the game the designer wants to make.

How Much Stuff?

One simple way to look at a game is by asking how many game systems and elements the player needs to master to feel competent. For example, a typical shooter might have ten weapons; a real-time strategy game might have fifteen units per side; a role-playing game might have twenty spells available. New players can often be intimidated by the sheer quantity of new concepts and options a game presents to them, and the time pressure of a real-time game only makes this learning experience an even greater challenge.

When first prototyping the original Civilization, Sid Meier originally built the game as a real-time simulation. Inspired by Will Wright’s SimCity, he tried to extend the concept to a global scale. He quickly found, however, that players were overwhelmed by the high number of new game systems they needed to juggle at once. After all, SimCity had no diplomacy, no trade, no combat, no research, and definitely no marauding barbarians. Thus, he changed course and rebuilt his prototype as a turn-based game, and the phrase “just one more turn” entered the gaming lexicon.

Designers always should be aware that each game can only contain so much “stuff” before the center cannot hold, and the experience overpowers the senses. By removing time pressure, turn-based games allow players to adjust the learning curve to their own needs. Veterans can still play quickly, but new players can take their time poking around the interface and thinking through their moves.

Thus, turn-based games are generally more accessible than real-time ones. It is no surprise that many of the most popular casual games are turn-based, from staples like Solitaire and Minesweeper to PopCap’s stable of Bejewelled, Bookworm, and Peggle.

Deterministic or Chaotic Play?

At their core, turn-based and real-time games play to different strengths. One example is the question of whether an experience should be deterministic or chaotic. With the former, success often depends on knowing exactly what the results of one’s actions will be; in Puzzle Quest, for example, the player needs to know that when a row of four skulls disappears, the other pieces will fall in a specific way so that a new column of consecutive red gems might form. Just because some luck elements are involved – such as the unknown new pieces which fall from the top – doesn’t mean that the player isn’t mapping out an exact series of events in her head. This sequential gameplay is one of the core strengths of turn-based games.

On the other hand, chaotic, unpredictable gameplay is a strength of real-time games. When players first spot a heavy-medic combo in Team Fortress 2, they know that they are probably in trouble, but the sequence of events to follow is so varied that players know it’s impossible to overanalyze the situation. A sniper could kill the medic. An explosion might knock the heavy off a platform. A spy might sneak up behind them. An event on the other side of the map might encourage one side to simply abandon the area. Real-time games support chaotic gameplay best because, with the added pressure of a shared clock, players are not able to reduce each situation down to a repeatable series of moves and counter-moves.

Multiplayer or Single-Player?

Another divide which defines the different strengths of turn-based and real-time games is whether the focus of the experience is multiplayer or single-player. Generally speaking, multiplayer games work best in real-time wheras turn-based games usually focus on single-player sessions. Turn-based games, like Advance Wars and Civilization, have only a tiny, hard-core multiplayer audience. On the other hand, real-time games with similar themes, such as Command & Conquer and Age of Empires, respectively, gained much of their popularity from their multi-player modes.

The reason for this divide is clear – waiting for another player to finish his turn is anathema to fun – so designers looking for a synchronous, multiplayer experience almost always prefer real-time games. However, because no one else is waiting, designers of purely single-player games give themselves the option of using turn-based elements whenever convenient, to either add some spice or allow more strategic play. For example, the single-player game Fallout 3 allows players to pause real-time combat and enter V.A.T.S. mode to strategize which enemy body parts to target, even displaying the exact probability of success for each possible choice. Similarly, the Baldur’s Gate series is a hybrid model, with real-time combat that pauses depending on certain player-selected events, such as when a character receives damage or a new enemy becomes visible.

Breaking the Rules

Indeed, these games are but a few of the many games that blur the line between “pure” turn-based and real-time systems. For example, what about turn-based decisions with a time limit, such as Madden‘s play-calling clock? What about X-Com, with its crunchy real-time strategic shell surrounding a gooey turn-based tactical core? Or the Total War series, which does the exact opposite? What about Europa Universalis, which is technically real-time but plays out so slowly that it “feels” like a classic, sprawling turn-based strategy game. How about asynchronous Web-based games like Travian, which play out over months instead of minutes, eliminating the time pressure but keeping the multi-player benefits of real-time play? What about Bang! Howdy, which plays as a typical tile-based tactical wargame, except that each unit’s turns regenerate in real-time? In reality, a vast continuum stretches from one extreme to the other, and most games find a space somewhere in the middle.

Therefore, the most important thing to focus on is not the labels themselves but what types of gameplay they represent. For example, the tower-defense game Plants vs. Zombies is ostensibly real-time, but its characteristics are more in line with traditional turn-based games. Besides being solely a single-player game, the gameplay itself is strictly deterministic, even moreso than many turn-based games. The map consists of five tracks along which the zombies progress, each with exactly nine slots on which to place defensive plants. Furthermore, the zombies’ behavior is entirely predictable – Pole Valuting Zombies will always jump over blocking Wall-nuts, even if that means falling right into the jaws of a Chomper plant. The game may look chaotic to an observer, but – like most tower-defense games – the strategic play is built upon predictable enemy behavior. The real-time mechanics simply provide time pressure, not the other qualities usually associated with the format, such as chaotic play or a multi-player mode.

Likewise, Boom Blox is a turn-based game which eskews the usual strengths of the format. In the game, players have a discrete number of throws during which to knock down various block-based structures. Unlike most turn-based games, however, Boom Blox is a very chaotic affair, with unpredictable physics-based game mechanics. Furthermore, unlike Plants vs. Zombies, in which players’ actions take place on a precise 5-by-9 grid, players of Boom Blox use strictly analog controls to point at the screen and then “throw” the ball with the WiiMote. Chaos theory dictates that an identical series of throws will almost never happen twice in a row. Furthermore, this unpredictable nature coupled with the very short turns (each only a single throw) makes Boom Blox an excellent multi-player game, a rare feat for turn-based video games.

Thus, in the end, deciding whether to make a game real-time or turn-based is less important than deciding which aspects of those formats are most relevant to the overall design. As they say, one needs to learn the rules to know how to break them.

The following was published in the May 2009 issue of Game Developer magazine…

The designers of Puzzle Quest have a frustrating burden to bear – everyone thinks they are a bunch of dirty cheaters. The game centers on a competitive version of Bejewelled, in which players duel with an AI to create the most “match-3” colored patterns.

The problem comes from how the pieces on the gameboard are created – when, for example, a column of three green orbs is lined up and removed from play, new pieces fall in to take their place. However, sometimes, these three new pieces happen to be of all the same type, which means that a new match is automatically made, and the player scores again. The odds of such a result are low (around 2% for getting three of the same colors in a row), but they are still high enough that a player will see it many times with enough games played.

Of course, the AI is playing the same game, so the player will see this lucky match fall into the enemy’s lap as well. At this point, human psychology takes over. Because the new pieces are hidden from view, how does the player know that the computer is not conducting some funny business and giving itself some free matches?

The human mind is notoriously bad at grasping probability, so many players are convinced that the AI is cheating. The developers have pledged over and over again that everything is fair and even, but whether they like it or not, the player experience has been affected by the simply possibility of cheating.

Trust Me

Games do not start with a player’s trust – this trust needs to be earned over time. Our audience is well aware that we can make a game do whatever we want under the hood, so the transparency and consistency of a game’s rules contribute significantly to player immersion. The worst feeling for a player is when they perceive – or just suspect – that a game is breaking its own rules and treating the human unfairly.

This situation is especially challenging for designers of symmetrical games, in which the AI is trying to solve the same problems as the human is. For asymmetrical games, cheating is simply bad game design – imagine the frustration which would result from enemies in Half-Life warping around the map to flank the player or guards in Thief instantly spotting a player hiding in the shadows.

However, under symmetrical conditions, artificial intelligence often needs to cheat just to be able to compete with the player. Accordingly, designers must learn what cheats feel fair to a player and what cheats do not. As the Puzzle Quest team knows, games need to avoid situations in which players even suspect that the game is cheating on them.

Cheating is not the same thing as difficulty levels – by which the players are asking the game to provide extra challenges for them. Cheating is whether a game is treating the player “fairly” – rewarding them for successful play and not arbitrarily punishing them just to maintain the challenge. Unfortunately, in practice, the distinction between difficulty levels and cheating is not so clear.

Show the Mechanics

Fans of racing games are quite familiar with this gray area. A common tactic employed by AI programmers to provide an appropriate level of challenge is to “rubberband” the cars together. In other words, the code ensures that if the AI cars fall too far behind the human, they will speed up. On the other hand, if the human falls behind, the AI slows down to allow the player to recover.

The problem is that this tactic is often obvious to the players, which either dulls their sense of accomplishment when they win or raises suspicions when they lose. Ironically, games which turn rubberbanding into an explicit game mechanic often becomes more palatable to their players.

For example, the Mario Kart series has long disproportionately divvied out rewards from the mystery item boxes sprinkled around the tracks relative to the riders’ current standings. While the first-place racer might receive a shell only useful for attacking other lead cars, players in the rear might get a speed bullet which automatically warps them to the middle of the pack.

These self-balancing mechanics are common to board games – think of the robber blocking the leader’s tiles in Settlers of Catan – and they don’t feel like cheating because the game is so explicit about how the system works. Thus, players understand that the bonuses available to the AI will also be available to themselves if they fall behind. With cheating, perception becomes reality, so transparency is the antidote to suspicion and distrust.

Cheating in Civilization

Sometime, however, hidden bonuses and cheats are still necessary to provide the right challenge for the player. The Civilization series provides plenty of examples of how this process can go awry and drive players crazy with poorly-handled cheating.

Being turn-based, the developers could not rely on a human’s natural limitations within a real-time environment. Instead, Civilization gives out a progressive series of unit, building, and technology discounts for the AI as the levels increase (as well as penalties at the lowest levels). Because of their incremental nature, these cheats have never earned much ire from the players. Their effect is too small to notice on a turn-by-turn basis, and players who pry into the details usually understand why these bonuses are necessary.

On the other hand, many other cheats have struck players as unfair. In the original version of the game, the AI could create units for free under the fog-of-war, a situation which clearly showed how the computer was playing by different rules from the human. Also, AI civilizations would occasionally receive free “instant” Wonders, often robbing a player of many turns of work. While an AI beating the human to a Wonder using the slow drip of steady bonuses was acceptable, granting it the Wonder instantly felt entirely different.

How a cheat will be perceived has much more to do with the inconsistencies and irrationality of human psychology than any attempt to measure up to some objective standard of fairness. Indeed, while subtle gameplay bonuses might not bother a player, other, legitimate strategies could drive players crazy, even if they know that a fellow human might pursue the exact same path as the AI has.

For example, in the original Civ, the AI was hard-wired to declare war on the human if the player was leading the game by 1900AD. This strategy felt unfair to players – who felt that the AI was ganging up on the human – even though most of them would have followed the same strategy without a second thought in a multi-player game.

In response, by the time of Civ3, we guaranteed that the AI did not consider whether an opponent was controlled by a human or a computer when conducting diplomacy. However, these changes still did not inoculate us against charges of unfairness. Civ3 allowed open trading – such as technology for maps or resources for gold. An enterprising human player would learn when to demand full price for their technologies and when to take whatever they could get – from a weak opponent with very little wealth, for example.

We adapted the AI to follow this same tactic, so that it would be able to take whatever gold it could from a backwards neighbor. To the players, however, the AI’s appeared to be once again ganging up against the human. Because the AI civs were fairly liberal with trading, they all tended to be around the same technology level, which led the player to believe that they were forming their own non-human trading cartel, spreading technologies around like candy (or, in the parlance of our forums, “tech-whoring”).

Perception is Reality

Once again, perception is reality. The question is not whether the AI is playing “fairly” but what is the game experience for the player? If questions of fairness keep creeping into the player’s mind, the game needs to be changed. Thus, for Civ4, we intentionally crippled the AI’s ability to trade with one another to ensure that a similar situation did not develop.

The computer is still a black box to players, so single events based on hidden mechanics need to be handled with great care. Sports game developers, for example, need to be very sensitive to how often a random event hurts the player, such as a fumble, steal, or ill-timed error. The dangers of perceived unfairness are simply too great.

Returning to our original example, the developers of Puzzle Quest actually should have considered cheating, but only in favor of the player. The game code could ensure that fortunate drops only happen for the human and never for the AI. The ultimate balance of the game could still be maintained by tweaking the power of the AI’s equipment and spells – changes which appear “fair” because they are explained explicitly to the player. The overall experience would thus be improved by the removal of these negative outliers that only serve to stir up suspicion. When the question is one of fairness, the player is always right.