I thought I'd open this article with a quote from Chris Hecker, creator of Spy Party.
At IndieCade 2011 this year, I led a discussion on the idea of depth in games with my friend Paul Sottosanti... We decided we don't really know what depth in games actually is, so instead of trying to give a lecture about it and flail around, we simply asked the audience what they thought. ~ Chris Hecker
Polling the masses is not a bad idea. Gamers have good instincts, a statement I've made before. Surprisingly (and not surpringly if you're a fan and follower of radiolab) taking the average of a group response is a great way to zero in on a subject. Starting with boardgamegeek.com and ending on gamasutra.com comments, the following are quotes followed by my comments.
What's the difference between complexity and depth? I would use them interchangeably when describing a board game! ~Richard Morgan
Depth and complexity are related in an asymmetrical way. While greater depth requires more complexity, more complexity doesn't require greater depth. So I can see why many would confuse and conflate the two terms. However, using them interchangeably is not a good idea.
Many of Reiner Knizia's games are not complex (easy to teach), but they have a lot of depth to them (many important choices with lasting effects)...Go isn't complex (easy to teach), but has a lot of depth (many interesting choices with long term weight). ~Jorune
Thinking of non-complex games in terms of games that are easy to teach is pretty accurate. After all, with fewer complexities to a game, there are less rules to consider and therefore it should be easier to teach. Keep in mind that games are very complex yet the rules are very simple and easy to teach. Take a Spelling Bee for example. The rules are, they say a word and you spell it correctly. Do this every time and you win. Yet there are thousands of words to learn and tricks to learning them well. So complexity of games isn't about learning how to play. It's more about considering all the play elements in the system. This is not to mention that gameplay dynamics are complexities that fuel emergent possibilities. So while a game can feature few rules (complexities), if there are enough gameplay dynamics the game can still be hard to teach.
Jorune goes on to describe depth as having "many important choices with lasting effects." If by "important choices" he means interesting choices, then he's on the right track. But "important choices" can be interpreted as choices necessary to win. If this is the case, important choices are present in linear games, straight forward games, and unbalanced games with a dominant strategy. If by "lasting effects" Jorune means consequences that ripple forward in time or actions that have dynamic effects, he's right again. Both of these are helpful in creating systems of interesting choices.
As to depth vs. complexity, it seems to me that they're closely linked to the "easy to learn, hard to master" distinction. Something complex is hard to learn, something deep is hard to master. Go, as someone said, is deep but not complex; I imagine certain bad games are complex but not deep. I'm guessing that complexity and depth correlate positively, especially when it comes to hobby games that try to present a limited number of meaningful options, and that try to be noob friendly by making basic strategy and resource management easy to figure out. ~ Jacob Nushmut
Jacob hits the nail on the head. As I've explained, depth and complexity are closely linked. Games are hard to master probably because of a balance of interesting choices, where there are enough dynamics, variables, mechanics, and interplay in the system so that there are many strategies and counters to anticipate, execute, and choose from. With so many emergent possibilities, the skill ceiling becomes high thus making the game difficult to master.
Jacob associates bad games as being very complex and not deep. I think many of us share the same view. Like I explained in my series Design Space: Infinite Undiscovery, putting in distracting, underutilized complexities into a system can have a negative effect on the player experience because learning these complexities takes a lot of time and energy of the player.
LOW DEPTH: Moves are always painfully obvious, not much decision making, game plays itself. ~Richard Ham
The above description of a gameplay system with low depth also describes linear and straightforward games. The idea is, if there is only one move to reasonably make, if the optimal or dominant strategy is not only known but obvious, if there's no real way to interfere with the actions of other players (interplay) then the game cannot be deep. With such games there is less of a dynamic system for players to engage with to overcome challenges in different ways. Rather linear, straightforward levels challenge players to execute on a series correct steps.
Depth – the Knowledge of How: Good fighting games have little depth to their combat system. (Say what?) This sounds like crazy talk, but listen: you must divorce yourself from the misconstrued and often synonymous meanings of depth like lots of moves, tactical , execution heavy, or even skill. Depth is none of these things. Depth is the measure of the number of times your player must learn How to do something; this includes every new system, but not, as I will show you, every new attack. This is an important distinction, as multiple moves can be mapped to the same “how” ~ Mike Birkhead
Mike is right when he explains that depth is not the same as having lots of moves (complexity), what is tactical (general plans of action), execution heavy gameplay (mechanics, controls, action frequency), and skill (DKART). Of course depth isn't any of these things. This is as far as Mike's insight goes. When Mike defines depth he conflates depth with skill floors ("number of times [a] player must learn") and mechanics input types. All of these considerations fall under a game's design space and mechanics design which are ways of dividing, organizing, and understanding the range of a game's complexity. In other words, Mike suggests that depth is actually a type of complexity, which is wrong.
Testing the Depth of Experience: Games are about more than playing. Games offer players the potential to engage in meaningful experiences that tap into the full spectrum of human emotions. While the potential may be limitless, games to date have struggled to provide experiences that deliver the emotional impact found in traditional media. ~Gaming Analytics Brochure
Like many, the researchers or writers of this brochure use depth in a way that describes a range of emotional experiences. While I won't get into it here, I think the statements that most make when comparing games to "traditional media" are skewed at best. As I'v explained, works can create depth of emotions, experiences, or ideas through the building up of their complexities. To convey more complex emotions, experiences, ideas works have to present more complexities in a clear way. When I talk of depth of gameplay, I specifically refer to a kind of experiential depth, which is the meaning the comes from the gameplay interactivity. While video game can convey a range of different kinds of depth, only looking for emotional depth will cause you to miss the depth of gameplay.
The great number of choices is one of the reasons why these games can have a lot of depth (“strategic depth” is the phrase sometimes used). There can be a lot of strategy in the game because there are a lot of plausible choices. ~Lewis Pulsipher
Strategy is simply a specific plan of action (most likely to gain an advantage); the more specific the better. You can form a strategy for linear games and open games alike. A great number of choices not does equate to gameplay depth or strategic depth. This is not to mention that if a game is not balanced well, lots of choices can be rendered unviable because of stronger possibly dominant strategies. Poor balance hurts gameplay depth.
Depth, in gameplay, means that the gameplay elements *combine* in a way that there are many layers of elements that you could consider when you play... Giving a lot of choice doesnt increase depth by itself, it just increase variety. Deep games typically allows the player to plan their actions several steps ahead. Poor players will only form short, obvious plans while good players will form long plans that combines the gameplay elements in unexpected manners to achieve a surprising result. ~Mathieu MarquisBolduc
When Mathieu says elements need to "combine" to create many layers to consider, he's on the right track. As we learned with interesting choices, the emergent combination of mechanics, dynamics, variables, and interplay is what really allows for a gameplay system to explode with viable possibilities. He's right again about choice. As I clarified above, more choices in and of itself does not increase gameplay depth.
Planing "several moves ahead" is a handy way of thinking about deep gameplay systems (see my videos on beating Mega Man 10 bosses). But players can think moves ahead in linear or solvable gameplay challenges too. If a gameplay challenge is solvable that means there's a dominant strategy; dominant strategies can't exist in systems of interesting choices. So, I wouldn't trust being able to think moves ahead as a good test for whether or not a gameplay system is deep.
Don't miss the last line of the above quote. Do you see how Mathieu adds in the part about "unexpected" and "surprising" results. While emergent possibilities are often surprising, and emergent possibilities are needed for gameplay of interesting choices (deep gameplay), You can have deep gameplay where nothing "unexpected" happens. The fact of the matter is, with more emergent systems you're more likely to eventually see novel gameplay scenarios that only skilled players can reach after battling back and forth through the deep gameplay system. But even if you don't, even if you play by the book, the gameplay is still deep.
Chess and go are deep games because of how the simple gameplay elements combine to form interesting patterns, and force players to form increasingly complex and lengthy plans. Tic-Tac-Toe isnt so deep because the short number of steps in the game limits the length of the plan the players can have, which means its very easy to select the ideal move at any time. If you want an example of an insanely deep game, play Knights in the Nightmare on the DS. All of the gameplay elements link to others in some interesting way.
Of course you have to add some uncertainty so that players dont always repeat the same plan with success. ~Mathieu MarquisBolduc
First, Knights in the Nightmare is not a deep game; it is a very cluttered and complex game. Though it has many wrinkles and other gameplay dynamics, the gameplay doesn't feature enough interplay or clarity to be deep. Without clarity, making "informed choices" (which is required to make interesting choices) is too difficult.
I think that Mathieu express some real insight when he says that a game needs some "uncertainty" to be deep. As I concluded in my series Interesting Choices: Interesting Gameplay, it is very difficult to create gameplay of interesting choices without including enough variables, mechanics, dynamics, and interplay. My experiment with Fictive RPG showed that a purely turned-based back and forth battle struggles to create gameplay of interesting choices. The complexities and the dynamics of the system had to be significantly increased to produce the results we were looking for. So, dynamics like 2D or 3D space, real-time elements, and even random elements are powerful tools to help interesting choices emerge. Tick-Tac-Toe doesn't use enough space to be very dynamic in its 3x3 grid. The space gets used up too quickly. It is too easy to figure out the ideal move thus turning all games played by moderately skilled players into a draw. (For a fantastic podcast program on Tic-Tac-Toe click here) Go features plenty of space and more rule complexity to allow for deep gameplay. And chess uses less space than go but more mechanics variety in its pieces.
If I had to give my own answer it would be, "The depth of a game is the number of distinctly different game states that can be reached without a/the player(s) making a mistake" ~Johnathan Walsh
Johnathan certainly presents an interesting way of thinking about depth. Without a clear language of terms to define a concept like gameplay depth, it's easy to slip into definitions that are difficult to express explicitly in words or to measure (probably due to their subjectivity). Knowing what we know about skill, the game-mental state, metagames, and mixups, what exactly would constitute making a mistake? Players of many different types of games commonly take hits to gain other kinds of advantages. After all, advanced Chess and Advance Wars strategies involve sacrificing and trading pieces. Also, most games aren't won or lost with just one mistake or move. Therefore the interplay and depth continues in the resulting gamestates thus making it hard to pinpoint where a mistake happened if at all.
The spirit of Johnathan's definition is pointed in the right direction, though. Imagine two players competing and trying to win at every opportunity. If they can explore many different game states that are distinct from each other without making a mistake, this may be possible because both players are countering each other's counters back and forth. That's as much credit as I can give Johnathan's definition.
A deep game creates meaningful mechanics-driven play at high skill levels. The game generates decisions with enough nuance that even a master-level player won't always get them right. More choices aren't necessary. Poker is deep, but often there are only two possible moves. Yet the decision between those moves is a mind-twister. What matters is the quality of the thought process behind the play decision. Don't demand a formal definition. Depth is a property of decisions, and decisions are in the mind. And the mind isn't a good subject for formal logical definitions. ~ Tynan Sylvester
We have to be careful about statements like this. If we assume that "meaningful" play is gameplay of interesting choices then of course it's mechanics-driven. What else would gameplay be driven by? And if we assume that these generated "decisions" are gamestates, I'm not sure why the mistakes of master-level players is important to the concept of depth. Players of all levels make mistakes due to mixups, lacking skills, or unforced execution errors. Looking at how some players make mistakes is a very unfruitful, roundabout way of analyzing game design.
I don't think Poker is a very deep game. It's built out of a simple double blind system that allows players to bluff their way in and out of tricky situations. Like Rock Paper Scissors, Poker is a fairly simple game where players try to manipulate and read their opponents. The probabilities of the hands players may have are complexities that increase the learning curve but not necessarily the depth of the interplay. Making a guess is always a "mind twister." It's just that those who come out on top find ways to make the most educated guesses while playing within their limits.
Depth is not a property of decisions. And shying away from trying to devise a formal definition avoids dealing with what the word "depth" actually describes. Depth is not an emotion or a feeling. It's a quality of complex systems.
Tynan is on the money. The depth of a game equals how wide a skill gap it allows players to establish to other players. This definition corresponds to what is normally meant when we say a game is "deep". ~Bisse Mayrakoira
The skill gap, or the distance between the skill floor and the skill ceiling of a game, is not depth. The skill gap deals with a game's difficulty design and skill ceiling. Defining depth by skill doesn't accurately capture the meaning of the term. For rhythm-action games if hitting every note perfectly defines the skill ceiling, then barely getting by with the lowest score defines the skill floor. Regardless of the skill gap rhythm-action games are not deep. They're typically very linear games. Just because games of deep gameplay are more difficult to master (because no one simple strategy can win, i.e. you have to learn the whole system to be successful) it's common to conflate depth with skill-based play. Pros being able to crush new players is not exclusive to deep games.
You hit the nail on the head with "the designer must ensure that some of these choices are not obvious, and that no particular decision is always the better one." That's depth - but it's in the mind, not in the game. Which is why I don't think formal, objective definitions work well. ... Here's another definition of depth: The skill level after which a player's performance in the game stops improving. Once you reach the limit of the game's depth, you can learn more, but you won't do better. ~Tynan Sylvester
Tynan is correct in identifying that the conditions for interesting choices is what creates depth. He still thinks that depth is in the mind. This kind of approach is pushing on philosophical levels that we don't need to entertain to get to the bottom of what depth in game design is and how it works.
Still, it's worth pointing out that the way Tynan goes about devising definitions approaches the issue of what depth is from odd, yet inefficient angles. By focusing in on the point where increasing knowledge of a game doesn't improve performance (ability to win), Tynan in a backwards way highlights the asymmetrical relationship between depth and complexity. Because a work can easily have more complexity than depth, there can clearly be some complexities that are not important for winning. Complexities that don't affect gameplay and viable options are in some ways obsolete and have nothing to do with the depth.
"Depth is the opportunity for mastery. ~ Jesse Tucker"
You can master any kind of system, deep or not. People have mastered Guitar Hero by working for perfect high scores. People are making TAS videos of perfect completions and speed runs of games. The opportunity for mastery is always there with games, even very simple games like Tic-Tac-Toe. Mastery is simply getting close to or reaching the skill ceilling of a game or its metagame.
[Depth is] not about out-thinking the opponent or anticipate his moves or being smarter. It's about controlling your opponent. As we add depth to a game, it means the players have more tools to achieve such thing. The less depth there is, the more it is dumbed down to the simple execution. More dumbed down than that, it's all about the situation (like the basic rock-paper-scissors or Halo or battlefield 3 with character classes and handicaps). ~Christian Philippe Guay
Christian is right in his opening statement. Depth is not about out-thinking the opponent, anticipating moves (yomi/reading), or being smarter (more knowledge skills). Players can use these tactics in deep games and shallow games. When he says depth is about "controlling your opponent" I believe he's saying depth is about interplay and the mechanics that work to create functional counters. In other words, depth isn't in the mind; it's in the gameplay rules and interactions that are governed by these rules.
While I wouldn't use the phrase "dumbed down" Christian's next statements also have a lot of truth to them. If you don't have a game of interesting choices, then the gameplay probably has a dominant strategy. If there's a dominant strategy, then competition is essentially a race to see who can execute on the known strategy. Think competitive Guitar Hero. Christian then explains that without real-time execution skills in a system (timing, reflex, dexterity), then competition is simply about knowing the dominant strategy or the obvious match up strengths. Christian is right to focus on depth being a system feature rather than a mentality or strategy players apply, but he goes too far when he tries to explain non-deep gameplay experiences.
So I think depth is a combination of the tools players are presented with, the versatility of the tools, how the rules and dynamics effect the tools and how players interpret the intended use of the tools and the rules. ~David Serrano
David essentially explains that depth is a combination of player tools (mechanics, the versatility of these tools (variables/properties), and how the rules affect the tools (dynamics). These are 3/4 of the essential features needed to create gameplay of interesting choices. He's only missing interplay, which is the most important feature. Unfortunately David adds a statement about what players interpret as the "intended use" of the mechanics and rules. What players intend and what the developers intend are not important factors in any objective, effective analysis or term of game design.
The depth of a game is how far you have to get into it before you lose your sense of wonder of it. If you can read a dozen books, play a million games, play someone you've played a thousand times before, and still go "wow, that was new" at the end, that's a deep game. ~Eric R
Again, player expectations and "wonder" are non-factors here. Depth has nothing to do with how unique or novel an idea, experience, or concept is.
As you can see, many gamers get really close to understanding what depth is and what kinds of game design elements create it. There are a few more topics I want to discuss before closing out. Stay tuned for part 3.