Diablo 3 - item sets

Modern item games like Diablo 3 (D3) use a mechanic called sets: when used together, certain items unlock particular bonuses. For example in D3, Litany of the Undaunted increases attack speed, The Wailing Host increases crit chance, and used together they give 15% extra gold from monsters. Item sets is an old mechanic - the Diablo 2 expansion already had some in 2001.

Sets in D3 are a great mechanic for at least two reasons. First, sets let developers encourage the use of certain skills. Since the bonuses from set items nearly always provide more damage than regular non-set items, players use them. For example, the Marauder set for Demon Hunters requires the use of sentries, a skill that would not be used otherwise because its AI for picking a target is unpredictable. Second, set items are a great mechanic also because they give players a goal. When I dropped my first set item and saw the set bonuses, I immediately wanted other items in the set.

Sudden increase in power

End-game starts after reaching level 70. Reaching level 70 by yourself takes roughly 15 hours. Difficulty from then on can be measured by the Greater Rift (GR) level your character can reach. Set bonuses are so powerful that they make your character jump multiple GR levels at once. For example, going from 5 set items to 6 can double your character's effective damage or toughness, and make you reach 5 or 6 GR levels higher. This explains why the Ring of Royal Grandeur, which reduces the number of items needed for set bonuses by 1, pretty much a wild-card for all your sets, is such a game-changer. These sudden increases in power sometimes surprise players, but I think each bump makes them suddenly feel very powerful. Interestingly, back in 2013, sets used to be as good as non-set legendary items.

Vague descriptions or hidden mechanics?

The descriptions of D3 set bonuses are often vague, and require the player to check the forums and Youtube videos for details. Here are two examples.

Marauder set

This is a Demon Hunter set. The 2-piece bonus is straightforward: it gives 500 dexterity (on top of the approximately 500 dexterity already contributed by each set piece).

The 4-piece bonus makes the Companion skill call all possible companions (instead of only one). Do passive effects from the Companion skill (e.g. the boar increases life regeneration) apply as well? And do all active effects trigger when I use the skill? The answers are not written in the description, but people figure it out quickly by trying.

The 6-piece bonus reads: Sentries cast your equipped Hatred spenders. After trying it out, I realized that sentries have a different rate of fire for each spender: Cluster Arrow (massive area damage) seems to happen only every 5 shots, whereas Elemental Arrow (small multi-target damage) the rest of the time. Looking at high-level Demon Hunters, most wear Tasker and Theo, which increases the attack speed of your pets by 40-50%. Are sentries pets? (Yes!) And how can I make my sentries use Cluster Arrow more often? (You can't!) Theorycrafters figured it all out by analyzing game frames one by one and sharing their findings. But is the average player supposed to read the forum to improve their character?

Zunimassa set

This is a Witch Doctor set. The 2-piece bonus gives 250 intelligence and grants 30 Mana per Kill. Is it only when my character performs the killing blow on a monster? Does it also work when it's one of my pets? Does it also work when it's another player?

The 4-piece bonus reads: Your Fetish Army (FA) lasts until they die. This is straightforward, and it made me think about the passive skill Fetish Sycophants (FS). FS seems to combo well with FA: When you hit enemies with your spells, you have up to a 10% chance to summon a dagger-wielding Fetish to fight by your side for 60 seconds. There are several problems with this apparent FA-FS synergy.

First, why the up to? What makes the rate be less than 10%? That is where theorycraft comes to the rescue. The community found out that one can have at most 15 active FS at the same time. So the rate of FS trigger is 10% until 15, at which point it becomes 0%. The description of FS should also mention this cap of 15.

A second problem is the easy confusion between the two types of fetishes. 1) Witch Doctors can have many pets: a Gargantuan, zombie dogs, FA fetishes, FS fetishes, and mimics. FA and FS are both fetishes, so intuitively, they must benefit from the same bonuses. 2) Why excluding FS from the 4-piece bonus when the effect from the Carnevil helm applies to both FA and FS? 3) The distinction between FA and FS is not for game balance: in practice, it's very easy to maintain 15 FS active all the time by speeding through monsters.

Why so vague?

I can see several reasons:

• Practicality: the developers want to be able to modify the bonus (through hotfix or patch) without modifying the description.
• Brevity: a precise description may require too much space in the item tooltip.
• Practice: figuring it out by trial is more visceral than by just reading the description.
• Theorycraft: explaining everything spoils the fun of theorycrafters.

Uselessness, sub-optimality, and combinatorics

Some sets are clearly underpowered compared to others. The Witch Doctor Invoker set and the Demon Hunter Shadow set are only useful when your character gets hit. Sadly, in D3, the best defense is offense: the goal is to kill monsters quickly enough that they don't kill you. Therefore these sets end up never being used (except the 2-piece Shadow set in hardcore mode, maybe?).

The Natalya set is not useless, but rather suboptimal. Both the 2-piece and 3-piece bonuses increase damage slightly and enhance mobility (more discipline means more Vaulting). The 4-piece bonus reduces the cooldown of Rain of Vengeance by 2 seconds for each enemy you kill. RoV has a base cooldown of 30 seconds, and does 1000% area damage for 5 seconds, so the set seems very interesting. In practice however, it is difficult to keep monsters grouped in an area for 5 seconds. So while some players use the 2- and 3-piece bonus, nobody cares about the 4-piece bonus. I wonder if the set would be more used if the cooldown was reduced by 2 seconds for every enemy hit (instead of killed).

ArcheAge boasts 120 classes, but it's only because players can pick 3 skill trees among 10, ie C(10,3) = 120 different combinations of skill trees. I don't think that all combinations are efficient, but ArcheAge achieves such diversity simply by leveraging combinatorics on 10 coherent sets of skills. In D3, a player using a Demon Hunter can pick 6 active skills among 24, so that's a total of C(24,6) = 134k different builds. Add to this that each active skill has 4-5 runes, and that there are also another 4 passive skills (5 if we count the Hellfire Amulet) to pick among 18. That's billions of combinations! Yet the only sustainable Demon Hunter builds actually played are minor variations around the same 6 skills. That is because the Marauder set forces players to pick these skills. Moreover, I really liked combining multiple 3- and 4-piece sets together, but the 6-piece Marauder took all the spots. I wish D3 had 1) more 4-piece sets and fewer 6-piece sets, and 2) combinations between sets, not just between sets and legendary items (e.g. Marauder and Tasker and Theo)

Diablo 3 - the item game

In item games, the main goal of players is to continuously upgrade their gear. Diablo 3 (D3) is the perfect example: kill monsters in order to drop better gear in order to kill monsters faster. Bungie just released Destiny, an item-game FPS budgeted with half a billion dollars. Yet Destiny could learn from Diablo 3. So here are some thoughts about the item game in D3.

Prevent farming ...

In D3, like in D2, the drops are completely random: with a few exceptions, nearly any item can drop from any monster or wreckable object (e.g. jars). The odds are just higher for harder monsters, and way lower for wreckable objects. The exact drop rates are secret (except the 10% legendary drop rate from Kadala). This secrecy has led to various rumors and tinfoil hat theories about how loot can be influenced.

D3 has, or used to have, farming spots such as the Decaying Crypt, but they were mostly for XP, not for drops. In D3, farming boss monsters actually brings fewer drops than farming normal or elite monsters. This contrasts with Diablo 2, where players were grinding bosses like Baal or Diablo for XP and loot. So in a way, the grind in D3 is less boring than in D2.

... Yet allow farming

As of October 2014, there are 2 exceptions to what I just wrote: 1) bounty rewards like RoRG or Helltrapper, and 2) Hellfire Amulet.

The RoRG was introduced in February 2014. It is a mandatory item to reach the game's highest difficulty levels. Players have to camp Act-1 bounties to get one with good rolls. To farm as quickly as possible, players join co-op games to split farm: instead of spending 15-20 minutes completing the 5 bounties together, they each complete a bounty in 5 minutes. I am surprised that the developers did not see it coming: split farming is very clearly not how we want players to play the game. Yet nearly a year later, they still have not changed the bounty system.

The Hellfire Amulet is not as mandatory compared to the RoRG. But its bonus is so useful that all of the top players have it. Farming it is somewhat more fun than farming for RoRG, since it is a quest in itself: a) hunt for the 4 Keywardens on the game's largest maps to obtain 4 keys, b) combine the 4 different keys into a portal, c) kill 2 super bosses at once, a somewhat more difficult task than the Keywarden hunt, and d) combine 4 super bosses' loots to obtain a Hellfire Amulet.

The Reaper of Souls expansion

From launch in May 2012 until the retirement of the Auction House (AH) in February 2014, players were mostly buying their gear from the AH, and sometimes grind-crafting it. They nearly never dropped it themselves. Legendary weapons had 7-8 affixes. After the AH retired, Loot 2.0 arrived, and the expansion Reaper of Souls (RoS) shortly after that. Legendary weapons now have 4 primary and 2 secondary affixes. Secondary affixes do not matter much (e.g. more XP when killing a monster), so RoS drastically reduced the item entropy.

The expansion also reminded me of Blizzard's somewhat elegant solution to a common MMO problem. Most MMOs in the early 2000s had the same problem: players who have been playing for a year have too much of a head start compared to players who have been playing for 3 months. New players are hopeless, especially in PvP situations. World of Warcraft solved this problem with what I call expansion gating: WoW vanilla capped the character level at 60 and item level at 92. Until the first expansion came out to increase these two caps, players were gated there. The advantage of expansion gating is that it gives the same chance to old and new players. The main drawback (if any) is mudflation. Diablo 3 is no different: level-70 items have twice more DPS than level-60 items. Thus when the expansion launched, players threw away all the gear they had acquired before.

Few links to other end-game activities

Item games have a great loop, but it is not enough in itself. D3 launched in May 2012. The Auction House (AH) launched in May 2012 too, so players could play two games in one: the action RPG and the auction game. Note that you did not need to play the aRPG to play the auction game, but you did need to buy gear off the AH to play the aRPG well. Had it been the opposite, I think the game would have been much better.

In July 2012, the developers realized that the item hunt is just not enough for a long-term sustainable end-game. Since launch, the game also allowed players to hunt for achievements and start new characters (in softcore or hardcore). In August 2012, the developers added the leveling up grind through 100 Paragon levels. Every Paragon level increased the chance to drop an item and the amount of gold dropped by 3%. In February 2014, Paragon levels became infinite, and the 3% bonus was removed. Clans and communities were also added in February 2014. Since August 2014, players can compete on the greater rift leaderboards, and start new seasonal characters (in softcore or hardcore). Interestingly, the item game is completely independent of all other end-game activities (except the AH and the original 100 Paragon levels increasing magic find and gold find). In other words, the item game of Reaper of Souls could be directly copied into another game without having to also copy the other activities.

Assist bundles in Forza 4 and 5

Forza Motorsport 4 is a realistic simulation racing game. If they want to, players can handle the clutch, tire-wear, and other minute racing details. For beginners, the game provides assists that take care of these details automatically. For example, the Braking and Steering assists make turning easier, the Line assist shows the optimal path to follow, and the Transmission assist takes care of switching the gears. For a description of the assists, check these websites.

While I was at Microsoft Research during the Summer of 2013, my mentors and I looked at patterns of progression in FM4. Among the things we published, we found that players rarely used the assist bundles shipped in FM4. FM5 came out in November 2013. This post describes how the FM5 designers used our findings on FM4 to improve the assist bundles.

Assists in FM4 and FM5

Here are the assist bundles shipped in FM4.

	Easy	Medium	Hard	Advanced	Expert
Steering	Assisted	Normal		Simulation
Stability	ON		OFF
Traction	ON			OFF
Brakes	Assisted + ABS		ABS only	OFF
Transmission	Automatic			Manual	Manual + clutch
Trajectory Line	Full		Braking only		OFF
Damage	Cosmetic	Limited		Simulation

Below are the FM4 bundles we suggested, based on player data in Career mode.

	Easy	Medium	Hard	Advanced	Expert	Comments
Steering	Assisted	Normal		Simulation		Unchanged
Stability	ON		OFF			Unchanged
Traction	ON			OFF		Unchanged
Brakes	Assisted + ABS	ABS only		OFF		ABS-only from Medium onwards
Transmission	Automatic		Manual		Manual + clutch	Manual from Hard onwards
Trajectory Line	Full	Braking only		OFF		Bumped down: shifted all cells to the left.
Damage	Cosmetic	Limited	Simulation			Simulation from Hard onwards

And below are the bundles shipped in FM5.

	Easy	Medium	Hard	Pro	Veteran	Comments
Steering	Assisted	Normal				Simpler: now binary. In Custom bundle, Assisted steering forces Assisted brakes.
Stability	ON			OFF		Bumped up
Traction	ON				OFF	Bumped up
Brakes	Assisted + ABS		ABS only			OFF available in Custom bundle.
Transmission	Automatic				Manual	Bumped up. Clutch available in Custom bundle.
Trajectory Line	Full		Braking only			OFF available in Custom bundle.
Damage	Cosmetic			Simulation		Simpler: now binary.

In short, the bundles in FM5 are easier than their FM4 equivalent because the Stability, Traction, and Transmission assists have been bumped up. Clutch transmission, ABS-OFF, and no trajectory line are only available in a Custom bundle. The FM5 designers did not exactly follow the bundles we suggested. Why is that? See below.

Assist progression

For each race number, we look at how much of the player base still has an assist enabled. The goal is to see how fast players disable an assist. The graph below shows exactly this.

Let's take the Transmission assist as an example. In the first race, the Transmission is automatic for 80% of players (the orange line starts at 0.8), manual without clutch for 15% (the space between the orange and brown lines), and manual with clutch for 5% (the brown line starts at 0.95). Even among the players who reach 100 races (17% of the total player base, cf gray line), only 15% use a manual transmission with clutch. That's why in FM5, manual transmission with clutch is only available in a Custom bundle: very few players use it. Same story for the Trajectory Line-OFF and ABS-OFF assists. In the end, the FM5 designers actually used our findings in their product!

Of course, we need another study to assess whether FM5 players are actually using the default FM5 bundles or not.

A note on Rewind

When you miss a turn, you can press Y to rewind the game and try the turn again. In FM4, the ability to rewind is an assist. Turning the assist OFF grants a 20% credit bonus at the end of a race. In FM5, each rewind costs 1% of the race's credit. I like this change for several reasons:

• In FM4, I enabled rewind in case I needed it during a race. But I only rewinded every 3-4 races. 20% was a lot of credits missed, though, so it felt a bit frustrating.
• A fixed price encourages players to rewind as much as they want. So, to get more bang for the buck, they increase the difficulty of the AI opponents, and rewind every time they don't make a perfect turn. This is the same lame trick as saving-and-rerolling in RPGs. Racing this way is excruciating. It also takes longer to complete a race, so the amount of credits gained per hour may actually be lower with more difficult AI.
• FM5's rewind cost is proportional. This is advantageous for players who rewind rarely, and disadvantageous for those who rewind dozens of times per race.
• I prefer paying the cost automatically, in the stats screen at the end of a race, rather than manually, through an assist menu before the race.

Using achievements for analytics, retention, or skill

Achievements can have many purposes in a game.

For analytics

At GDC 2010, Bruce Philips from Microsoft showed how he used Xbox Live achievements to evaluate progression and campaign completion in a dozen FPS. These achievements already existed, and were determined by the game designers, yet provided very useful for analytics.

Traditionally, achievements are binary: you have unlocked it, or you haven't. You can treat achievements as milestones that the player reached. Milestone achievements include: FPS campaign milestones or Forza 4's "import data from Forza 3".

Achievements can also take several levels. For example, Clash of Clans' Release the Beasts achievement takes 4 values: 0 when you start, 1 when you unlock Archer, 2 when you unlock Wall breaker, and 3 when you unlock Dragon. This achievement, by itself, suffices to segment the player base into new, intermediate, advanced, and expert players. It's a double-win: players have more achievements to go for, and you get a better picture than with a binary achievement.

An achievement can keep counting even after it's been unlocked; for example, Clash of Clans' Gold Grab has 3 steps (4 values) but keeps track of the gold you looted. That way, achievements can also be numerical, not just binary or Likert-like.

Achievements can be even more complex and hold metadata such as when you unlocked it, how many days it took you to unlock it, after how many tries, in how much time, and so on. With this metadata, you can label player behavior more precisely. For example, a Clash of Clans player may unlock Gold grab 3 after 3 months where another would only take one month. The later certainly plays much more (number of sessions, session length) than the former.

For retention

Achievements provide long-term goals to the player. Moreover, they can be made so the player always has a near-complete achievement in sight. For example, you reach 490/500 mortars destroyed in Clash of Clans' Mortar Mauler achievement. You play another hour to destroy 10 mortars and get the 10 gems, but by then, another achievement has reached near-completion too, and you could play another hour.

Retention achievements don't always involve grinding. They can encourage the player to explore the design space.

For skill (or luck)

For example, in FTL Repair back to full health with only 1 HP remaining. Skilled players can risk it, for the thrill. But other players can also wait for it to happen by itself.

Other FTL examples include completing a mission in less than X minutes, or not using any weapon until sector 5. Or even taking 5 turns in a row in the card game Ascension.

Player Experience Panel, Phillips 2010

Player Experience Panel, Phillips at GDC 2010.

(slides, mostly about FPS games)

Each dot represents the average number of days taken to complete a particular achievement. DLC achievements are farther because DLC were released later (not because they are harder or take more time to complete).

Box gameplay peaks when new DLC is released: new content does increase the number of people playing. However, later DLC packs do not peak as much as the first DLC pack.

Influence of gameplay on skill in Halo: Reach

Huang et al. Influence of Gameplay on Skill in Halo Reach, 2013

Data: 3m player data (entire population) for the first 7 months of Halo Reach, and 70 players in a survey. Mixed methods: use survey data to help explain the big dataset.

Most played mode is Team Slayer: from 3v3 to 5v5, one point per kill, first team to reach 50 kills. Match ends after 15 min.

Player skill metric: TrueSkill's mean μ. More frequent players have bigger μ drop at week 1, but their μ increases faster over the weeks.
The longer the break between two games, the bigger drop in skill. It takes 10 games (3h of gameplay) to regain the skill lost after a break of 1 month.
Most of the top 100 players use the DMR (same range as sniper rifle) and sniper rifle.

Stress: appraisal, coping, and physiology

Notes from the first few weeks of a class on stress by Sally Dickerson taught throughout Spring 2012.

Basics

Eustress = positive/healthy stress. Example: wedding, vacation. As opposed to distress. Three phases of stress: stressor, appraisal, and response.

The stressor is the eliciting event; examples are being stuck in traffic, having an exam, or arguing with your partner. Stressors break homeostasis, our stability with the environment. A stressor can be acute or chronic. Durations of exposure to stressor vs duration of perceived threat vs duration of stress response.

The response happens at all levels: emotional (e.g. fear), physiological (e.g. BP increases), and behavioral (e.g. running away). The response aims at bringing back homeostasis. If it lasts for too long, sickness appears because of the general adaptation syndrome.

Appraisal

Evaluation/interpretation of the harm, threat, and overwhelmingness of the stressor to determine the response. Individual- and context-specific. Individuals who are told beforehand that "pain is going to happen" have stronger physiological response to a stressor than individuals told "it's just a formality, nothing too big". Appraisal consists of the primary appraisal and coping.

Primary appraisal

The individual estimates the importance/meaning of the stressor, and its implications on her well-being. "This is the most important day of my life" vs "No big deal". Three types of primary appraisals:

Type	Description	Emotions generated	Physiological response	Example with stressor = "just got fired"
Harm/loss	The damage has already been done	sadness, anger	damaging	"Everyone looked at me packing my stuff"
Threat	Possibility of future damage	anxiety, fear	damaging	"How am I going to pay the rent?"
Challenge	Potential to overcome and profit.	excitement	positive/healthy, smaller than harm or threat	"Let's find a better job"

Primary appraisal moderators:

• sense of control. If the individual feels (no need to actually be) in control = less stress. But inappropriate sense of control increases stress: individuals blame themselves for an event they actually could not influence, especially if the event is big: "it's my fault if my car's brakes broke and it caused an accident".
• predictability. Know when stressor happens (and/or does not happen) reduces stress. Unless stressor very frequent or very rare, or horrible outcome (e.g. earthquake).
• ambiguity. If information on the stressor is vague, stress increases.
• centrality. If the outcome is important to the individual, stress increases.

-	Optimists	Pessimists
Face problems	actively	passively
Receive positive events	wrt themselves, in general and absolute terms	wrt other people, in specific and relative terms
Receive negative events	wrt other people, in specific and relative terms	wrt themselves, in general and absolute terms
Example: just got fired	"my skills were not a good match for that company" (external)	"i am a failure" (internal), "I can't do anything" (global), "I'll never get another job" (absolute)

Coping

The individual estimates how well she can cope with the stressor. If she estimates she does not have enough resources to cope with the stressor, the stress response will be bigger. Coping can happen before, during, or after a stressor, and it varies in time. When it happens before, it is called proactive coping (e.g. keep water bottle packs and a torch light at hand in case of a disaster). Even when given information, if people feel like they can not change the outcome, or if they underestimate the problem, they may not pro-actively cope.

Avoidance or minimization are effective coping strategies for short-term stressors. Vigilance and confrontation consist of gathering information or take direct action, and are more effective in the long-run, but fail if the information is of poor quality (e.g. individual googles "soar throat" symptoms and finds herself on a page about a deadly disease). Social support from others is a form of coping; the individual reduces her stress response by receiving moral support, information about the stressor, or tangible resources (money, workforce, ...) to overcome the stressor.

Coping can be problem-focused, emotion-focused, or both. Problem-focused coping is constructive (e.g. studying for an exam), and effective when the individual can have an impact on the stressor. Emotion-focused coping does not address the problem, but rather regulates the individual's emotions cognitively (how people think about the stressor, e.g. "it could be worse"), or behaviorally (doing something, e.g. jogging or eating chocolate to feel better). Emotion-focused coping is effective when the individual does not have control on the stressor.

In general, optimists deny less and cope better than pessimists. For instance, Type A individuals are competitive, easily provoked, fast-paced, and impatient. They have more risky behaviors, are less likely to receive social support, and have bigger physiological responses. Hence, they are more sensitive to stress. Moreover, according to a 2006 study (see also the pdf), Big 5's Neuroticism is related to distress and emotion-focused coping, while Conscientiousness is related to task-focused coping.

Methods for assessing stress

• After an unpredictable/random trauma (e.g. a disaster): from groups or individuals. Problem: getting a baseline before the stressor happened. Solution: compare with similar groups or individuals who were not exposed to the trauma.
• Life events: go through individual's recent events to assess her current stress level. Depending on the category of the individual, each event has a standard weight (e.g. for undergrad students, "death of relative" = 100 points, "got a ticket" = 20 points).
• Daily stressors: going over recent events or maintaining daily diary (prompted by researchers every day at the same hour).
• Lab experiments: standardized stressor, influence on appraisal (but appraisal ultimately depends on the individual), can measure physiological response, but not generalizable.

Physiologically

Cortisol is a hormone released by the adrenal gland in response to stress. Its function is to have the body generate energy by breaking body fat into glucose. In the circadian rhythm, it naturally peaks at wake up, and falls at sleep time.

Cognitive tasks such as mental arithmetic increase the concentration of cortisol in the blood. Public speaking increases it even more. The two combined generate more than the sum of each. Public speaking exposes our differences with other people, and invites criticism: it is a social evaluative threat. This threat is increased if we are captured on permanent record, in front of a critical audience, or compared to others negatively. On the other hand, emotion induction (such as watching a scary movie) or exposure to noise do not influence the cortisol level.

Uncontrollability increases the cortisol level. Hence, false feedback to a stressful task will increase the cortisol level. Changing the task difficulty on the fly, harassing the individual under stress, or adding noise and distractions increases stress. An uncontrollable social-evaluative threat generates the biggest cortisol response, and a slow stress recovery: the cortisol level remains high longer.

Novelty and diversity also seem to increase the cortisol response. Facing many stressors at a time seems to increase the cortisol level logarithmically with the number of stressors. On the other hand, facing a stressor as a group reduces the individuals' cortisol response. Similarly, in a 1991 study, women's stress response was found to be smaller if their pet rather than their friend was with them: as opposed to the friend, the pet provides support without judging.

Using Social Psychology to Motivate Contributions to Online Communities - Beenen 2004

Notes from Using Social Psychology to Motivate Contributions to Online Communities, by Beenen et al. 2004

• 830 respondents who rated rare movies on a movie recommendation website.
• Theoretical framing: social loafing/free riding
• Findings: the contribution of an individual may increase if:
  • his contribution seems unique to the group
  • specific benefits (ie individual-only or group-only) are not mentioned. The best is to not mention the benefits at all.
  • goals are specific
  • goals are framed for the group rather than for the individual
  • goals are challenging (but still within reach)

Connections:

• reasonable goals echoes intersubjective flow from Celia Pearce
• In MMOs, tank, DPS, and healer are unique roles. Does that make them play more/better towards the group?

The aesthetics of gameplay: a lexical approach

The aesthetics of gameplay: a lexical approach
Zagal and Tomuro
MindTrek'10

See the PDF or the ACM page.

Primary Elements of Gameplay Aesthetics

Aesthetics cluster	Words in cluster	Description
Pacing	fast, stressful, dull, tedious	The perception of how often game events occur.
Scope	endless, vast, immense, minimal	The size of the possibility space afforded by a game.
Complexity	simple, short, complex, uncomplicated	The measure, or sense, of the number of parts in a system and how they are interrelated.
Demands	hardcore, experienced, retro, demanding	The requirements imposed upon the player by the gameplay
Cognitive Accessibility	deep, unusual, twisted, intricate,	The measure, or sense, of the opacity of a system and the challenges it poses in understanding it.
Impact	addictive, boring, overwhelming, visceral	What we feel games “do to us” when we play them, and how they make us feel.

• Analyzed nearly 400k user reviews posted before April 2009 on gamespot.com. 8k games covered by reviews from 112k users.
• 40% of user reviews contain the word gameplay
• Method: Stanford Parser to perform part-of-speech tagging. Matrix of (723 adjectives total that precede and modify the word gameplay) x (5000 most frequent words that occur before or after the adjective, ie context words, ie words that give a context to the adjective). Cells of the matrix contain number of occurrence of an adjective with a context word. Run kmeans on the matrix to obtain k=30 adjective clusters. (Compared to k=10 or 20, k=30 generated better-looking clusters). Two adjectives are similar (and put in the same cluster) if their context word distributions are similar. Then, give a name to each cluster based on the adjectives it contains.
• Only 2 clusters about narrative elements. Therefore, players have no difficulties separating the formal or mechanical aspects (game mechanics) from their narrative interpretations (representation).
• AI does not emerge as a cluster. Possible reasons: no language to describe game AI, or games AI are not sophisticated enough, or a too recently marketed topic to feature in reviews.
• Genre does not emerge as a cluster.
• Limitations: Gamespot population = 95% males, lots of colloquial words disappeared in cleaning phases.

My remarks

• A group like "fast FPS gameplay" may have been considered as "fast gameplay" because FPS is not an English adjective, and the Stanford parser only looks at English adjectives. Since genre adjectives are not English but rather specific of gamer communities (e.g. "FPS", "RTS", "JRPG", etc.), genre did not appear in clusters.
• It'd be interesting to know which game names occurred most often next to gameplay. For instance, "gameplay like Civilization" may be quite rare, but very meaningful when talking about a niche genre.
• If genre is a label of the dataset, then it could be interesting to cluster a matrix like adjectives x genre. Goal = see which adjectives are explaining most a genre.

Fundamentals of Game Design, ch 14: Strategy Games

Strategy = planning series of actions against the opponent(s). There's usually a large variety of potential actions. Analysis paralysis happens when players have to wait for the other to be done thinking about his next move. In RTS, decisions have to be taken quickly. The basic mechanics of strategy games involve units and the factories that produce them. There can be diplomacy if the scenario is long enough. The attributes of units can be: (max) health, (max) armor, atk, ammo, aspd, area of effect, range, and others ...

Melee unit's value (eg footman) = max HP * shot power * aspd * accuracy * range * walk speed
Ranged static unit's value (eg tower) = max HP * shot power * aspd * accuracy * range^2/2. Squared because the area defended increases quadratically. Halved because units can generally only cover one side/half, the one side towards the enemy.

Most RTS make little use of line of sight and terrain realism; a unit on top of a hill could see further, a unit behind a hill could be hidden from those behind it, units have atk/def/... bonus when they are in their favorite terrain.

Gold is too important for war for mines to be spread out randomly. Spreading randomly means randomly-chosen players get a random advantage from the start, which is unfair. Mines randomly spread also means that players will hunt for mines instead of fighting strategically against each other. Large mines should be positioned symmetrically if they are decisive. Random mines should be smaller and not be decisive for winning.

Lanchester's laws: 1- In melee combat, army strength is proportional to number of units because each fighter can engage only one enemy at once. 2- In ranged combat, units can concentrate their power on a single enemy. When 1 unit is attacked by 3 archers, its life decreases 3 times faster, and it can only attack one of them, ie 1/3 of the enemies. Therefore, 3 ranged units are 3*3=9 times stronger than a single unit (whether ranged or not).

Imagine the tight and strong negative feedback loop: "wounded units attack weaker". Then players have to play sub-efficiently all the time, and they're going to wage attrition skirmishes, not big epic battles.

Do not block or forbid certain units or skills in a particular level. Instead, make the level so that this unit or skill is very inappropriate. Ex: to prevent the player to use air units, give the opponent lots of anti-air missiles. To prevent the use of iron, set the victory condition to "collect lots of iron".

Upgrades

Upgrades can apply to a single unit (veteran units have +1 dmg), all units of a particular kind (grunts get +2 atk), all units of all kinds (Iron Age = +2 def to everyone), or even the whole mechanics (production speed divided by 2). Upgrades can be unlocked by spending resources, time, achievement, ... The tech tree can be:

• totally open: player spends point in any tree she wants, like in WoW
• constrained: finish one branch to start another
• fixed: once player starts in a tree, only this tree is available for the rest of the game

Production and distribution

Production process should be concrete and visible, while the distribution process should be abstracted. Ex: plant farms for food = concrete food production. No supply lines as long as there are roads = abstract supply distribution. There are different shades and techniques for supply lines: troop caravans between cities in Heroes of Might and Magic IV, trade caravans between cities in Civilization series or Age of Empires, or Armored Personnel Carrier that transports troops and fuel in Advance Wars. Another approach is to have cities within a zone of influence to be supplied: cf the influence zone mechanics of Populous (you can only build in your area of influence), Civilization, and Black and White (you can only exert your god powers within your zone of influence).

AI techniques

• Game tree search, as used in games where there is a finite number of possible moves, such as Chess or Checkers. Problem: the search space increases exponentially, which is a problem for games like Go which have too many possible moves.
• Neural networks: patterns are identified after repeated exposure. Problem: training takes time, the system can hardly be tweaked, and adding new patterns means re-training the whole system.
• FSM: units transition from one state (walking) to another (shooting) because of events (enemy appeared in sight). Problem: the unit can only be in one state at once.
• Hierarchical FSM: FSM of the commander gives orders such as "take this hill" to captains. Captains have an FSM that gives orders to soldiers in the squad, such as "cover fire" or "make diversion". Each soldier has its own FSM as well: "if I see an enemy, run for cover". hFSM can create emergent behavior.

FDG 2011 comments

A few comments from FDG 2011. My points are [inside brackets], the rest comes from their respective authors.

In the last Madden NFL game, people tended to play the same kinds of games and rarely changed to different types/modes.

[The Player Experience workshop had roughly 5/15 papers accepted. 3/5 accepted paper authors were not here. What's the goal of a workshop then?]

Secondary game objectives should support the primary objectives, otherwise they distract, frustrate or make the player lose. Mario side-scrollers coins sometimes make the player go off-path, but the player always has to go from left to right. Player should be told when an objective is secondary.

Minimalist game design (from one of the designers of Osmos): few rules, few mechanics, few choices, deep (combinatorial) complexity (eg NP complete), simple controls, abstract, tightly-coupled systems.

CRPG guidelines: balance should be based on player expertise or avatar skills, not on character level or XP. Avatar background should affect the game. If the avatar is supposed to have lived in the game world for years, then the game should not remind the player of the avatar background, and NPC should not meet the avatar for the first time. [Possible solution: player's avatar could start as a toddler and ages as the player spends more time IG]

Weak ties make social storytelling. [Add to this that being socially active means connecting your weak ties together (you play the go-between). Therefore, in a distant future, there should not be any social storytelling anymore because everybody will be friend (ie strong tie) with everybody. In fact, Dunbar's number says you can't be friend with more than 120 people (the other people are just contacts, not actual friends). Hence, people will keep trying to (re)connect their weak ties together! Cf also Harris and Nardi's paper on collaborative play in WoW]

Mateas: computational media is a research field in which computer science is seen as a tool for expression.

If you want a domain to progress, and the industry does not care about that domain to progress, then you have to go try academia. [Maybe a good approach in many domains, but it does not work in MMOG because building one requires hundreds of man-years]

Frustration arises when player fails to overcome a challenge. Frustration makes players impatient.

[Literature] Game Balance ch10 - Economics and Multiplayer Dynamics

My notes from course 10 of the Game Balance class of Summer 2010, by Ian Schreiber.

Economy

In an economic system, players can generate, consume/destroy, or trade resources in a zero-sum fashion (what a player consumes is what another can not consume). Supply and demand curves:

• supply = f(price) is monotonic (increasing): if I sell for $5, then I also can sell for $10
• demand = f(price) is decreasing: if I accept to buy for $10, I also accept to buy for $5

Market price = where the 2 curves intersect. Prices fluctuate as players need or produce items. Prices fluctuate more if there are fewer players. Demand curves affect each other:

• substitutes: SP potion (+ casting Heal spell) is a substitute for HP potion. Increasing supply of X means decreasing demand of Y.
• item sets/collectibles: when together, sword X + shield Y give +10atk bonus. Increasing supply of X means increasing demand of Y.

The price per unit can increase or decrease depending on how many of that unit the player already has. If more units of the same kind brings increasing bonuses, then marginal cost decreases. If each unit costs more and more, the game is more stable and homogeneous.

Demand increases with scarcity. Example in FPS: ammo can be limited (player don't shot all the time, therefore it'd make sense if they died in one shot) or infinite (trigger happy, players should only loose a bit of life when they're hurt). In RTS, limited number of mines to get gold from means shorter games, whereas more and bigger mines means longer games (and more military encounters).

Closed-system = game systems that are self-contained, nothing outside of them can influence what's inside. Somehow, gold farmers open the closed economies of MMOGs, making them harder to design and control. The game should not allow players who have more RL money to have more power, it should just allow more options/variety. Experts using cheap/default CCG decks should beat novices using expensive/rare decks. Yet RL money could be used to speed up progression/avoid grinding.

Inflation happens in MMOs because the game is positive sum (money comes from quests and monsters). New players will never catch up unless negative-sum (sinks) or zero-sum elements are included. Negative-sum/Sinks can be: NPC, repair and death penalties, luxury items, or even tax richest players and give that money to poor players (Robin Hood transforming positive-sum into zero-sum). Zero-sum can be: player-bound/non-tradable items, quests can be repeated but reward only once. Nothing tradable also is a solution.

Trading mechanics

By giving players resources they do not need, they'll have an incentive to trade. Trading mechanics usually serve as a negative-feedback loop, especially within a closed economy. Players are generally more willing to offer favorable trades to those who are behind, while they expect to get a better deal from someone who is ahead (or else they won’t trade at all).

• future agreements: I give X now for Y now and Z later. Players could renege, making them more suspicious when trading with delays.
• scope: powerful resources (eg victory points in Catan) should not be tradable. Tradable resources become more fluid.
• time and phases: players can trade all the time, and trades could take effect at once. Or trading could be limited to certain phases (every 5 turns, or before player starts his building phase) and/or this phase could be timed (eg 5-min timer to bargain).
• evenness: gifts (0 for n) vs even trades (1 for 1) vs uneven trades (1 for n)
• quantification: trading can happen only once per turn/per hour, or as much as player wants. Number of exchanged objects may be bounded as well.
• tax: if trading coalitions are too powerful, put a tax as a cost to trade
• forced: I look at the cards in your hand and pick the best, and give you in exchange my worse card.

Auctions

Auctions = players' willingness to pay for a resource. Auctions work best when the actual cost is variable, different between players, and situational. Each time players decide how much the resource is worth to them, they are making an «interesting choice».

• Many types of auctions (increasing, blind, decreasing, ...),
• with different kinds of rewards (winner gets the entire lot, or first pick in the draft, and/or looser gets bonus or penalty),
• different payers (top bidder, top 2 bidders, top and bottom bidders, all players, ...),
• different recipients (bank = deflation, shared fund, or to other players),
• different events when no one bids (resource given to a random player, or more resources are added to the current resource and the auction restart, or resource is just discarded)

Misc. problems

Name	Problem	Solution
Turtling	Everybody shelters and nobody actually plays because attacking seems more costly and inefficient than defending and waiting for opportunities.	Give incentives to attack (when players wins, she gets more resources next turn), or force players to attack (player has to draw and play one card each turn, and 90% of cards are attack cards).
Kill the leader and sandbagging	Players recognize a clear leader, Players see their best chance to win as eliminating the leader, Players coordinate to attack the leader Players fear to become leader, and play suboptimally	Hidden scores make it impossible to know who is the leader, or make it obvious that eliminating the leader is not the best chance to win, or make the game non-PVP, or make players not able to team-up against another/give advantage when a player defends against many
Kingmaking	One player recognizes they cannot win, Player recognizes that they can give support to any leading player, Losing player chooses one leading player to win	Make players believe they can always win, or make it impossible to know which action will make a king, or make it impossible to choose who to make king, or simply do not allow last players to help leaders
Elimination	Player is killed at the beginning of the game and has to wait for the game to end	Players can only eliminate others if they are strong enough to eliminate all others, or the goal can be to collect points (instead of killing others), or when one player dies, the game stops immediately or within a certain time, and winner is current leader, or make the killed player take control of NPC, or make it interesting to look at other players playing (cf Mafia or Werewolf), or let killed players have goals as well (Cosmic Encounter or BSG)

Final note: balance is not always a must-have. Some games are ostensibly unfair but fun nevertheless. In single-player games, progression matters more than fairness. The unfairness of some one-against-many multiplayer games sometimes makes them fun.

[Literature] Game Balance ch7 - Advancement, progression and pacing

My notes from course 7 of the Game Balance class of Summer 2010, by Ian Schreiber.

Progression is ...	in games that are ...
absolute	PvE/single player
relative to other players	PvP/multiplayer

Flow has two problems: different player audiences have different skills, and players learn throughout the game.
Balance = overall game difficulty, does not solve these problems. Balance only matches audience expectation.
Progression/Pacing = keeping the player in the flow zone. As player skill increases, so do challenges. Progression ensures the game ends in the time frame said by the box (1min for arcade, 40h for RPG, etc.). If the game is endless, then progression = end-game rewarding structure(s).

When transitioning from mid- to end- or elder game, the objectives change from progressing to something else. Game designer has to find something for the player to do. Ex: WoW guild raiding or making your house cute in Farmville/Sims. Problems: some players may like the progression game but not the elder game. The power gathered during progression game should be available and enjoyable during elder game.
Tips:

• As playtesters test the game, they become experts => the game gets tuned harder => make the game easier at the end, and/or keep some playtesters for the end.
• Let players adjust the difficulty themselves (more challenging but also more rewarding levels or adjusting the difficulty level at any time). In PVP, difficulty adjustment should be voluntary (handicap, resources at the beginning, ...).

PVE

Perceived difficulty = (game power challenge + game skill challenge) - (player power + player skill), with:

• Game power challenge = stats (doubling opponents HP makes the game harder)
• Game skill challenge = new enemies or better AI, direct challenge to the player's skill (you need to play better) and not a player's power (you need more hit points to win). A game designer can control power-related, but not skill-related components of difficulty.

Large luck component or shallow mechanics: a short increase in player skill as the player masters what little they can at the beginning. Then skill plateau (player is as good as she can ever be). A minute to learn, a minute to master. This is the design of educational games (where skill is not the priority).

Giving practice zones where new weapons or powers are acquired makes players learn/increase their skill faster. Skill gating = progressively harder challenges, guarantee that if players complete a challenge, then they are ready for the next. Skill gating != practice zones.

Psychology: “reward schedule” or “risk/reward cycle”: you don’t just want the players to progress, you want them to feel like they are being rewarded for playing well. Reward not too rarely and not too often. Many small rewards are more efficient than a single big reward. Regular rewards = bad. Reward for something players were looking for (otherwise the game seems too easy) and not for a random event (eg "inflict exactly 123 dmg"). 3 kinds of rewards related to progression: increasing player power, level transitions, and story progression.

Increasing player power

If the most fun toy in your game is only discovered 2/3rds of the way through, that’s a lot of time the player doesn’t get to have fun. How do you actually keep the player engaged when you've given away all the cool toys early in the game? One way is 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. Warning: this is really hard to do in practice. You can also use other rewards more liberally after you shut off the new toys: more story, more stat increases, more frequent boss fights or level transitions. Also, toy upgrades.
Better shorten the game than have it too long and boring.

Level transitions

Each level takes a little bit longer than the last: fast progression at start engages player into the game, later levels can be longer because player wants to know the end of the plot.

Story progression

Story really IS a reward. There should be a match between story complication/climax curve and the difficulty curve. Ex: tutorial = exposition scene, miniboss = rising action, final boss = final climax. Final boss should not be as demanding on player skill as kill 10 rats.

Pattern: do not reveal the story only during level transition; instead, revealing additional background story immediately after a fight (even an easy one) makes players feel like they earned it. (But do not do that all the time otherwise it becomes predictble!)

PvP

Acquiring more power than opponents = primary reward. PvP has more options to play with than PVE because everything is relative, there's no defined level/stats to reach to be "strong".

negative feedback loops => more power when behind and less power when ahead => best player alternates => depends on opponents, no one is left behind (ex: Mario Kart with dynamic difficulty adjustment).
positive feedback loop => more power brings more power => best stays best => independent of the opponents, game ends faster, bad start is deadly (ex: League of Legends).

	positive sum	negative sum	zero sum
Definition	sum of all player resources increases over time	players lose power over time. Goal = lose power more slowly than opponents.	fixed amount of resources on the table
Example	Catan, Agricola	Chess	Poker
Positive feedback
Negative feedback			Solution: Each player spends time in the lead before one player's final blow ends the game.

When both players have realized who is going to win, the game should end quickly.

[Literature] A theory of Fun for Game Design

Raph Koster. 2004. A Theory of Fun for Game Design. Paraglyph Press.

Quotes taken from Koster's book. I did not try to put them together in a meaningful way, I just copy-pasted those I found most interesting.

ch3: What games are

The only real difference between games and reality is that the stakes are lower with games.
The more formally constructed your game is, the more limited it will be. Long-lasting games integrate variables from outside the magic circle.
Fun from games arises out of mastery.
With games, learning is the drug. Fun is just another word for learning.

ch4: What games teach us

Most of the game designers working professionally today are self-taught.
Games are viewed as frivolity.
Games almost always teach us tools for being the top monkey.
Most games encourage demonizing the opponent. Can we create games that instead offer us greater insight into how the modern world works?
There has not been a topologically different 2d shooter since [the first 2d shooter to have power ups and bosses and scrolling]. Unsurprisingly, the shooter genre has stagnated and lost market share.
Algorithm for innovation: find a new dimension to add to the gameplay

ch5: What games are not

One of the most self-defeating rallying cry in history: "it's just a game"
The part of games that is least understood is the formal abstract system portion of it, the mathematical part of it. Games need to develop this formal aspect of themselves in order to improve.
This is why gamers are dismissive of the ethical implications of games. They do not see "get a blowjob from a hooker then run her over", they see a power up.
Since games are generally about power, control, and those other primitive things, the stories tend to be so as well.
When games and stories are good, you can come back to them repeatedly and keep learning something new.
Getting emotional effects out of games may be the wrong approach. Perhaps a better question is whether stories can be fun in the way games can.
Different kinds of enjoyment:

• fun is the act of mastering a problem mentally
• aesthetic appreciation
• visceral reactions are generally physical and relate to the physical mastery of a problem
• social status maneuvers, intrinsic to our self-image and our standing in a community

Aesthetics is about recognizing patterns, not learning new ones.
Delight does not last. Recognition is not an extended process.
Fun is the feedback the brain gives us when we are absorbing patterns for learning purposes. Real fun comes from challenges that are always at the margin of our ability.
Fun is contextual. The reason why we are engaging in an activity matter a lot.

ch6: Different fun for different folks

Since brains have different strengths and weaknesses, different people will have different ideal games.
People will usually choose to play the games they are good at, that reflect their strength.

ch7: The problem with learning

Players try to find the optimal path to getting to the ultimate goal.
Exploiters are often the most expert players of a game.
Since we dislike tedium, we'll allow unpredictability, but only in the confines of predictable boxes, like games or TV shows. Unpredictability means new patterns to learn, therefore unpredictability is fun.
Those of us who want games to be fun are fighting a losing battle against the human brain because fun is a process and routine is its destination.
If there is not a quantifiable advantage to doing something [reward], the brain will discard it.
Successful games incorporate:

• preparation [choices made before a given challenge], otherwise it's chance. Can the player prepare in different ways and still succeed?
• a sense of space, otherwise it's trivial. Does the environment affect the challenge?
• core mechanics
• challenges [= content] otherwise it's too short. Can the rule set support multiple types of challenges?
• a range of abilities (otherwise it's simplistic). Can the player bring multiple abilities to bear on the challenge? At high levels of difficulty, does the player have to bring multiple abilities?
• abilities should require skill. Not requiring skill from a player should be considered a cardinal sin in game design.

A learning experience require:

• variable feedback (a greater skill should lead to better reward). Are there multiple success states (ie no guaranteed result)?
• high-level players can not get benefits from easy encounters or they will bottom feed.
• failure must have a cost. Player should have the ability to try again (with another preparation round).

ch8: The problem with people

Particular problems and solutions appeal to particular brain types.
Games are not there to fulfill power fantasies.
[The increasing complexity of games within a genre] has led to a priesthood of those who can master the intricacies. Newcomers can not get into them - the barrier for entry is too high.
Designeritis [= being] hypersensitive to patterns in games.
Given the lack of codification and critique of what games are, game designers have instead operated under the more guild-like model of apprenticeship. They do what they have seen work.

ch9: Games in context

The following chart can be applied to any medium.

User goal	Collaborative	Competitive	Solo
Constructive	Community Team game design	Job Commercial game development	Hobby Modding
Experiential	Performance PVE	Sport PVP	Audience Single player games
Deconstructive	Teaching Strategy guide writing	Criticism Hack and cheats	Analysis Writing this book

It's a lot easier to fail to respond to a painting than to fail to respond to a game.
The closer we get to understand the basic building blocks of games (...) the more likely we are to achieve the height of art.

ch10: The ethics of entertainment

For games to really develop as a medium, they need to further develop the ludemes, not just the dressing. By and large, however, the industry has spent its time improving the dressing [...] It's just easy relative to the true challenge.
The best test of a game's fun [is] playing the game with no graphics, no music, no sound, no story, no nothing.
Ethical questions [in games] are aimed at the dressing.
The ludemes themselves can have social values.
As a medium, we have to earn the right to be taken seriously.

ch11: Where games should go

For games to really step up to the plate, they need to provide us with insights into ourselves.
When you feed a player [with a game], right now, we only know "fun" and "boring". Mastery of the medium of games will have to imply authorial intent. The formal systems must be capable of invoking desired learning patterns.

ch12: Taking their rightful place

Games need to develop a critical vocabulary so that understanding of our field can be shared.
Games will never be mature so long as designers create them with complete answers to their own puzzles in mind.

Epilogue

The challenge game designers face is "how do we create games that do not have one right answer?"
[Game designers] are not geeks in the basement rolling funny-shaped dice. Games deserve respect.