[In this in-depth design analysis, first published in the August 2009 issue of Game Developer magazine, Electronic Arts designer Soren Johnson (Spore, Civilization IV) looks at the myriad factors in the decision to make a game turn-based versus real-time.] 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 supplanted 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 Bejeweled, 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 multiplayer 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.