Tuesday, May 28, 2013

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Advancement, Progression and Pacing (Part V)

In Part I of this article, game designer and educator Ian Schreiber explains the reasoning behind using advancement, progression and pacing in games. In Part II, he discusses challenge levels in PvE.  In Part III, he explains how to handle the reward schedule in PvE.  In Part IV, he tackles challenge levels in PvP. In the final segment, he discusses the relationship between difficulty levels and pacing.

Flow Theory, Revisited 

With all that said, let’s come back to flow. There were two problems here that needed to be solved. One is that the player skill is increasing throughout the game, which tends to shift them from being in the flow to being bored. This is mostly a problem for longer PvE games, where the player has enough time and experience in the game to genuinely get better.

The solution, as we’ve seen when we talked about PvE games, is to have the game compensate by increasing its difficulty through play in order to make the game seem more challenging – this is the essence of what designers mean when they talk about a game’s “pacing.” For PvP games, in most cases we want the better player to win, so this isn’t seen as much of a problem; however, for games where we want the less-skilled player to have a chance and the highly-skilled player to still be challenged, we can implement negative feedback loops and randomness to give an extra edge to the player who is behind.

There was another problem with flow in that you can design your game at one level of difficulty, but players come to your game with a range of initial difficulty levels, and what’s easy for one player is hard for another.

With PvE games, as you might guess, the de facto standard is to implement a series of difficulty levels, with higher levels granting the AI power-based bonuses or giving the player fewer power-based bonuses, because that is relatively cheap and easy to design and implement. However, I have two cautions here:
  1. If you keep using the same playtesters, they will become experts at the game, and thus unable to accurately judge the true difficulty of “easy mode”; easy should mean easy and it’s better to err on the side of making it too easy, than making it challenging enough that some players will feel like they just can’t play at all. 
  2. Take care to set player expectations up front about higher difficulties, especially if the AI actually cheats. If the game pretends on the surface to be a fair opponent that just gets harder because it is more skilled, and then players find out that it’s actually peeking at information that’s supposed to be hidden, it can be frustrating. If you’re clear that the AI is cheating and the player chooses that difficulty level anyway, there are less hurt feelings: the player is expecting an unfair challenge and the whole point is to beat that challenge anyway. Sometimes this is as simple as choosing a creative name for your highest difficulty level, like “Insane.”
There are, of course, other ways to deal with differing player skill levels. Higher difficulty levels can actually increase the skill challenge of the game instead of the power challenge. Giving enemies a higher degree of AI, as I said before, is expensive but can be really impressive if pulled off correctly. A cheaper way to do this in some games is simply to modify the design of your levels by blocking off easier alternate paths, forcing the player to go through a harder path to get to the same end location when they’re playing at higher difficulty.

Then there’s Dynamic Difficulty Adjustment (DDA), which is a specialized type of negative feedback loop where the game tries to figure out how the player is doing and then adjusts the difficulty on the fly. You have to be very careful with this, as with all negative feedback loops, because it does punish the player for doing well and some players will not appreciate that if it isn’t set up as an expectation ahead of time.

Another way to do this is to split the difference, by offering dynamic difficulty changes under player control. Like DDA, try to figure out how the player is doing… but then, give the player the option of changing the difficulty level manually. One example of this is the game flOw, where the player can go to the next more challenging level or the previous easier level at just about any time, based on how confident they are in their skills. Another example, God of War did this and probably some other games as well, is if you die enough times on a level it’ll offer you the chance to drop the difficulty on the reload screen (which some players might find patronizing, but on the other hand it also gives the player no excuse if they die again anyway). Sid Meier’s Pirates actually gives the player the chance to increase the difficulty when they come into port after a successful mission, and actually gives the player an incentive: a higher percentage of the booty on future missions if they succeed.

The equivalent in PvP games is a handicapping system, where one player can start with more power or earn more power over the course of the game, to compensate for their lower level of skill. In most cases this should be voluntary, though; players entering a PvP contest typically expect the game to be fair by default.

[This article was adapted from Ian Schreiber's course, Game Balance Concepts.]

Ian Schreiber has been in the game industry since the year 2000, first as a programmer and then as a game designer. Also an educator since 2006, Ian has taught game design and development courses at a variety of schools, and on his own without a school. He has co-authored two books, Challenges for Game Designers and Breaking Into the Game Industry.  

Wednesday, May 15, 2013

Advancement, Progression and Pacing (Part IV)

In Part I of this article, game designer and educator Ian Schreiber explains the reasoning behind using advancement, progression and pacing in games. In Part II, he discusses challenge levels in PvE.  In Part III, he explains how to handle the reward schedule in PvE.  Next, he tackles challenge levels in PvP.

Challenge Levels in PvP 

 If PvE games are all about progression and rewards, PvP games are about gains and losses relative to your opponents. Either directly or indirectly, the goal is to gain enough power to win the game, and there is some kind of tug-of-war between the players as each is trying to get there first. I’ll remind you that when I’m saying “power” in the context of progression, I’m talking about the sum of all aspects of the player’s position in the game, so this includes having more pieces and cards put into play, more resources, better board position, taking more turns or actions, or really anything that affects the player’s standing (other than the player’s skill level at playing the game). The victory condition for the game is sometimes to reach a certain level of power directly; sometimes it is indirect, where the actual condition is something abstract like Victory Points, and it is the player’s power in the game that merely enables them to score those Victory Points. And in some cases the players don’t gain power, they lose power, and the object of the game is to get the opponent(s) to run out first. In any case, gaining power relative to your opponents is usually an important player goal.

Tracking player power as the game progresses (that is, seeing how power changes over time in a real-time game, or how it changes each turn in a turn-based game) can follow a lot of different patterns in PvP games. In PvE you almost always see an increase in absolute player power level over time (even if their power level relative to the challenges around them may increase or decrease, depending on the game). In PvP, there are more options to play with, since everything is relative to the opponents and not compared with some absolute “You must be THIS GOOD to win the game” yardstick.

Positive-sum, negative-sum, and zero-sum games

Here is an important distinction in power-based progression that we borrow from the field of Game Theory: whether the game is zero-sum, positive-sum, or negative-sum. If you haven’t heard these terms before:
  • Positive-sum means that the overall power in the game increases over time. Settlers of Catan is an example of a positive-sum game: With each roll of the dice, resources are generated for the players, and all players can gain power simultaneously without any of their opponents losing power. Monopoly is another example of a positive-sum game, because on average every trip around the board will give the player $200 (and that money comes from the bank, not from other players). While there are a few spaces that remove wealth from the game and are therefore negative-sum (Income Tax, Luxury Tax, a few of the Chance and Community Chest cards, unmortgaging properties, and sometimes Jail), on average these losses add up to less than $200, so on average more wealth is created than removed over time. Some players use house rules that give jackpots on Free Parking or landing exactly on Go, which make the game even more positive-sum. While you can lose lots of money to other players by landing on their properties, that activity itself is zero-sum (one player is losing money, another player is gaining the exact same amount). This helps explain why Monopoly feels to most people like it takes forever: it’s a positive-sum game so the average wealth of players is increasing over time, but the object of the game is to bankrupt your opponents which can only be done through zero-sum methods. And the house rules most people play with just increase the positive-sum nature of the game, making the problem worse!
  • Zero-sum means that the sum of all power in the game is a constant, and can neither be created nor destroyed by players. In other words, the only way for me to gain power is to take it from another player, and I gain exactly as much as they lose. Poker is an example of a zero-sum game, because the only way to win money is to take it from other players, and you win exactly as much as the total that everyone else loses. (If you play in a casino or online where the House takes a percentage of each pot, it actually becomes a negative-sum game for the players.)
  • Negative-sum means that over time, players actually lose more power than they gain; player actions remove power from the game without replacing it. Chess is a good example of a negative-sum game; generally over time, your force is getting smaller. Capturing your opponent’s pieces does not give those pieces to you, it removes them from the board. Chess has no zero-sum elements, where capturing an enemy piece gives that piece to you (although the related game Shogi does work this way, and has extremely different play dynamics as a result). Chess does have one positive-sum element, pawn promotion, but that generally happens rarely and only in the end game, and serves the important purpose of adding a positive feedback loop to bring the game to a close.
An interesting property here is that changes in player power, whether zero-sum, positive-sum, or negative-sum, are the primary rewards in a PvP game. The player feels rewarded because they have gained power relative to their opponents, so they feel like they have a better chance of winning after making a particularly good move.

Positive and negative feedback loops

Another thing I should mention here is how positive and negative feedback loops fit in with this, because you can have either kind of feedback loop with a zero-sum, positive-sum or negative-sum game, but they work differently. In case you’re not familiar with these terms, “positive feedback loop” means that receiving a power reward makes it more likely that you’ll receive more, in other words it rewards you for doing well and punishes you for doing poorly; “negative feedback loop” is the opposite, where receiving a power reward makes it less likely you’ll receive more, so it punishes you for doing well and rewards you for doing poorly.

One interesting property of feedback loops is how they affect the player’s power curve. With negative feedback, the power curve of one player usually depends on their opponent’s power: they will increase more when behind, and decrease more when ahead, so a single player’s power curve can look very different depending on how they’re doing relative to their opponents, and this will look different from game to game.

With positive feedback, you tend to have a curve that gets more sharply increasing or decreasing over time, with larger swings in the endgame; unlike negative feedback, a positive feedback curve doesn’t always take the opponent’s standings into account… it can just reward a player’s absolute power.
Now, these aren’t hard-and-fast rules… a negative feedback loop can be absolute, which basically forces everyone to slow down around the time they reach the end game; and a positive feedback loop can be relative, where you gain power when you’re in the lead. However, if we understand the game design purpose that is served by feedback loops, we’ll see why positive feedback is usually independent of the opponents, while negative feedback is usually dependent.

The purpose of feedback loops in game design

The primary purpose of positive feedback is to get the game to end quickly. Once a winner has been decided and a player is too far ahead, you don’t want to drag it out because that wastes everyone’s time. Because of this, you want all players on an accelerating curve in the end game. It doesn’t really matter who is ahead; the purpose is to get the game to end, and as long as everyone gets more power, it will end faster.

By contrast, the primary purpose of negative feedback is to let players who are behind catch up, so that no one ever feels like they are in a position where they can’t possibly win. If everyone is slowed down in exactly the same fashion in the endgame, that doesn’t fulfill this purpose; someone who was behind at the beginning can still be behind at the end, and even though the gap appears to close, they are slowed down as much as anyone else. In order to truly allow those who are behind to catch up, the game has to be able to tell the difference between someone who is behind and someone who is ahead.

[This article was adapted from Ian Schreiber's course, Game Balance Concepts.]

Ian Schreiber has been in the game industry since the year 2000, first as a programmer and then as a game designer. Also an educator since 2006, Ian has taught game design and development courses at a variety of schools, and on his own without a school. He has co-authored two books, Challenges for Game Designers and Breaking Into the Game Industry.  

Thursday, May 9, 2013

May 2013: Branching Narrative

I recently spoke at the Writers Guild of America, East on a panel about Writing for Videogames.  And there it was, again:  the topic of branching narrative.  It struck me that this is what people think game writers do, once you make it clear that you don't actually program the game.  A PBS exec once said to me, "How in the earth do you do it?  I can't even imagine how that would be like."

Personally, I feel Branching Narrative can be a nightmare.  I was working on an ambitious game with branching narrative.  In the process of development, the game got whittled down and key portions were cut.  I remember re-writing the entire game 3 times.  If anything, I want to avoid branching narrative or at least limit it so that it doesn't become unwieldy.

Moreover, some games are actually linear stories, with the interactivity solely in the gameplay.  And some branching narrative aren't even what I would call games but interactive fiction.  Browsing through a couple Twine stories, I noticed the interactivity amounted to a Click to Proceed button since there was only one choice given to the reader (other than to quit reading the story).  Even when the interactivity is confined to small mini games interspersed in the story, I still feel unfulfilled when the gameplay is limited and doesn't advance the story.  It's like reading a chapter of the book, then playing a game of Peggle, then reading the book again.

What are your thoughts on branching narrative and meaningful game choices?  There are certainly games that focus directly on this.  How do you do this well?

I invite readers to submit an article on this topic.  Please read the submission guidelines first.  Thanks!

Wednesday, May 1, 2013

Advancement, Progression and Pacing (Part III)

In Part I of this article, game designer and educator Ian Schreiber explains the reasoning behind using advancement, progression and pacing in games. In Part II, he discusses challenge levels in PvE.  In Part III, he explains how to handle the reward schedule in PvE.

Rewards in PvE 

In PvE games especially, progression is strongly related to what is sometimes called the “reward schedule” or “risk/reward cycle.” The idea is that you don’t just want the player to progress, you want them to feel like they are being rewarded for playing well. In a sense, you can think of progression as a reward itself: as the player continues in the game and demonstrates mastery, the ability to progress through the game shows the player they are doing well and reinforces that they’re a good player.

One corollary here is that you do need to make sure the player notices you’re rewarding them. Another corollary is that timing is important when handing out rewards:
  •  Giving too few rewards, or spacing them out for too long so that the player goes for long stretches without feeling any sense of progression, is usually a bad thing. The player is demoralized and may start to feel like if they aren’t making progress, they’re playing the game wrong (even if they’re really doing fine).
  • Ironically, giving too many rewards can also be hazardous. One of the things we’ve learned from psychology is that happiness comes from experiencing some kind of gain or improvement, so many little gains produce a lot more happiness than one big gain, even if they add up to the same thing. Giving too many big rewards in a small space of time diminishes their impact. 
  • Another thing we know from psychology is that a random reward schedule is more powerful than a fixed schedule. This does not mean that the rewards themselves should be arbitrary; they should be linked to the player’s progress through the game, and they should happen as a direct result of what the player did, so that the player feels a sense of accomplishment. It is far more powerful to reward the player because of their deliberate action in the game, than to reward them for something they didn’t know about and weren’t even trying for. 
There are three kinds of rewards that all relate to progression: increasing player power, level transitions, and story progression.  

Rewarding the player with increased power

Progression through getting a new toy/object/capability that actually increases player options is another special milestone. Like we said before, you want these spaced out, though a lot of times I see the player get all the cool toys in the first third or half of the game and then spend the rest of the game finding new and interesting ways to use them.

Still, if you give the player access to everything early on, you need to use other kinds of rewards to keep them engaged through the longer final parts of the game where they don’t find any new toys. How can you do this?

Here’s a few ways:
  • If your mechanics have a lot of depth, you can just present unique combinations of things to the player to keep them challenged and engaged. (This is really hard to do in practice.) 
  • Use other rewards more liberally after you shut off the new toys: more story, more stat increases, more frequent boss fights or level transitions. You can also offer upgrades to their toys, although it’s debatable whether you can think of an “upgrade” as just another way of saying “new toy.”
  •  Or you can, you know, make your game shorter. In this day and age, thankfully, there’s no shame in this. Portal and Braid are both well-known for two things: being really great games, and being short. 
Rewarding the player with level transitions

Progression through level transitions – that is, progression to a new area – is a special kind of reward, because it makes the player feel like they’re moving ahead (and they are!). You want these spaced out a bit so the player isn’t so overwhelmed by changes that they feel like the whole game is always moving ahead without them; a rule of thumb is to offer new levels or areas on a slightly increasing curve, where each level takes a little bit longer than the last. This makes the player feel like they are moving ahead more rapidly at the start of the game when they haven’t become as emotionally invested in the outcome.  A player can tolerate slightly longer stretches between transitions near the end of the game, especially if they are being led up to a huge plot point. 

Rewarding the player with story progression

Progression through plot advancement is interesting to analyze, because in so many ways the story is separate from the gameplay: in most games, knowing the characters’ motivations or their feelings towards each other has absolutely no meaning when you’re dealing with things like combat mechanics. And yet, in many games, story progression is one of the rewards built into the reward cycle.

Additionally, the story itself has a “difficulty” of sorts (we call it “dramatic tension”), so another thing to consider in story-based games is whether the dramatic tension of the story overlaps well with the overall difficulty of the game. Many games do not: the story climax is at the end, but the hardest part of the game is in the middle somewhere, before you find an uber-powerful weapon that makes the rest of the game easy. In general, you want rising tension in your story while the difficulty curve is increasing, dramatic climaxes at the hardest part, and so on; this makes the story feel more integrated with the mechanics, all thanks to game balance and math.

Combining the types of rewards into a single reward schedule

Note that a reward is a reward, so you don’t just want to space each category of rewards out individually, but also interweave them. In other words, you don’t need to have too many overlaps, where you have a level transition, plot advancement, and a power level increase all at once.

Level transitions are fixed, so you tend to see the power rewards sprinkled throughout the levels as rewards between transitions. Strangely, in practice, a lot of plot advancement tends to happen at the same time as level transitions, which might be a missed opportunity. Some games take the chance to add some back story in the middle of levels, in areas that are otherwise uninteresting… although then the danger is that the player is getting a reward arbitrarily when they feel like they weren’t doing anything except walking around and exploring. A common design pattern I see in this case is to split the difference by scripting the plot advancement so it immediately follows a fight of some kind. Even if it’s a relatively easy fight, if it’s one that’s scripted, the reward of revealing some additional story immediately after can make the player feel like they earned it.

[This article was adapted from Ian Schreiber's course, Game Balance Concepts.]

Ian Schreiber has been in the game industry since the year 2000, first as a programmer and then as a game designer. Also an educator since 2006, Ian has taught game design and development courses at a variety of schools, and on his own without a school. He has co-authored two books, Challenges for Game Designers and Breaking Into the Game Industry.