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.

Improving the end-game of social strategy games

Improving the end-game of social strategy games

I removed Clash of Clans (CoC) from my iPad on August 20, 2014. The game had just reached two years old, and I had been playing it since February 2013. I played very actively (2-3 hours per day on average) until December 2013, then considerably slowed down (1 hour per week).

No new content

I think I slowed down, and eventually stopped playing mostly because no significantly new content was introduced. New content mattered a lot to me because I had reached Town Hall 10, the very end of the game, for many months. So far, the game has received four updates in 2014.

Month	Description
January	Introduced Hero abilities, which are not really a new gameplay feature, but rather a design fix to encourage players to use and upgrade their heroes. Great, and perhaps even necessary, but no impact on battle strategy or base design.
April	Introduced Clan Wars, a feature asked by players since the game came out. My clan was very excited, but we stopped Clan Wars after a couple weeks. We realized that the match-making algorithm alternated pairing our clan against once a much stronger clan, once a moderately weaker clan. Clan Wars require a lot of time and in-game resources, so we kept asking for enemy clans, but only attacked when we were sure to win. After a few weeks, we realized the Clan Wars rewards were not worth the frustration, so we stopped match-making.
May	Mostly usability tweaks.
July	Improved Hero abilities. Once again, this was more a design fix to encourage the use and upgrading of Heroes than a new feature.

Moreover, in these four updates, the Hog Rider received three nerfs, but my base still got trampled by mass-hog armies. (Yes, anti-hog base designs exist, but these designs are very vulnerable to air attacks). The Valkyrie was buffed twice, but it still was not enough to make her useful for her cost. To sum up the last 8 months, no new mechanic, be it a unit or a tower, was introduced, and I did not find the balance tweaks adequate.

Lessons for social strategy games

Troop synergies

The game was released with 10 basic units that make sense when used together. For example, the Giants are slow and target defenses so that the Healer can follow them without being hit. These synergies are expected: the team had time to iterate and polish before launch. But introducing new troops after launch is tricky: the new troops must 1) have an interesting gameplay element, 2) complement existing troops, and 3) keep existing troops useful.

The Minion is a perfect example: it is cheap and flying. This makes it a great complement for farming with Barbarians and Archers (called the BAM strategy). It is also great for high-level PvP when paired with Balloons (Balloonion strategy). And since it costs dark elixir and has low HP, it can't be used by itself.

The pricey Golem is another great example: it synergizes well with Wizards and Pekkas (GoWiWi strategy), which are necessary troops in high-level PvP. The Golem's production stats are perfect: 45 minutes to make, and a cost of 2.5 hours-worth of dark elixir, which is the same as Pekka. The Golem was clearly designed to be trained in parallel of Pekka. Plus Supercell must have made a lot of money from players gemming it!

On the other hand, the moderately expensive wall-jumping Hog Rider does not complement any other troop. Neither does the Valkyrie. Interesting ideas, but no synergy! Supercell keeps trying to fix them, so they may have realized that. Or maybe Supercell abandoned them completely, and has been working on more troops, such as the Spider, Centaur, or Yeti, which have not been released yet, but were leaked in July 2014.

More things to do in the end game

As the Town Hall levels go by, so does the average duration of building upgrades. For example, upgrades take 3-10 hours at TH3, 1-3 days at TH6, and 7-14 days at TH10. By TH10, the player should have 5 Builders, so the average time between two building upgrades is still 2-3 days. During these 2-3 days, players come back to the game only because their troops are ready for battle, not because they have something to do with their base. But by TH10, players have spent months being progressively conditioned to come back for their troops and not their base. So they still come back, but more and more reluctantly, since the rewards are less and less frequent. At some point, they unlearn the habit of coming back to play: what's the point when nothing seems to be happening? They eventually stop playing.

Possible solutions involve shortening upgrade times or providing more builders, but both may seem like Supercell would lose money. The game should at least give players things to do with their buildings (beyond collecting resources twice a day). The Bomb very short upgrade times have been a step in that direction. A crafting system like in Monster Legacy, or Angry Birds Epic, but applied to strengthening buildings, or increasing towers' rate of fire, may increase the game's lifespan even more.

Mobile crap - daily login

This series of articles is a rant about mobile game design. It may extend to console and PC gaming, but I only talk about what I experienced through most games featured on the iPad app store in the past year or so.

Designers could invent new mechanics to improve the core gameplay, and thereby improve retention metrics in the long run. But they cheat: they invent new mechanics to immediately improve retention metrics, thereby ignoring or forgetting to improve the core gameplay.

Mobile games try to maximize various metrics: their number of daily and monthly active users (DAU and MAU), the average session length, and so on. To do so, they introduce game mechanics that encourage players to come back every day or play longer. In games like Clash of Clans or Farmville, the come-back mechanic is the core game loop, so it is not a problem. Waiting and coming back is what these games are about. But in traditional fighting, racing, or match-three games, the only reason why players would come back or play longer is because they like the fighting, racing, or match-three mechanics, not because they like waiting.

More and more games have been adding come-back mechanics on top of their core gameplay. In 2004, World of Warcraft started granting a rest XP bonus to players who do not login for a long time. Blizzard designers originally implemented the rest mechanic to prevent hardcore players to level up too quickly. Beta-testers hated it, so Blizzard made it a reward for casual players instead of a punishment for hardcore players. Nothing changed mathematically, but players prefer mechanics if they are framed as a reward.

More recently in mobile games, Plundernauts has been giving out a welcome-back reward for logging in. They also give out bounties which must be completed within 24 hours - an incentive to play at least a few battles during the day, most likely in one session. 24-hour bounties are great for metrics such as the average session length, but they do not make the game more fun in the long run.

Puzzle and Dragons gives two login bonuses: 1) a consecutive login bonus, with rewards increasing every consecutive day, and reset the day the player does not login, and 2) a cumulative login bonus, increasing every day the player logs in, and never reset. Also, there are 5 exclamation marks for 7 lines of text in the login bonus message. By abusing the exclamation mark they over-emphasize my login, and it looks very amateur.

And finally, mobile games such as Birzzle or Mother of Myths show a daily login calendar when the player logs in. Some calendars focus on the week (4x7 cells), others on the month (5x6 cells). The calendar resembles an Advent Calendar, except 1) nothing happens at the end, and 2) the calendar mechanic is not properly tied to the core gameplay (receive more and more gold, or increasingly better gifts). The only point of the calendar is to keep people logging in for the rewards, not to have more fun playing the game.

A lot of mobile games have mediocre and dull core gameplay. These games are often sugarcoated in happy-shiny graphics and habit-forming mechanics. None of those improve their core gameplay. These games remain shallow.

Rewards, pacing, and dopamine

Rewards and pacing

There is something mysterious when people read through 1000 pages of Cryptonomicon, a 1999 novel from Stephenson, or through the thousands of pages of Martin's A song of ice and fire. What keeps people reading? Here are some rewards that both authors use throughout their books:

Reward	Pacing	Description
Character progression	Randomly (but fits the story)	The protagonist learns new skills, grows up, meets love, learns a lesson of life, or gets rich. We care about this character's well-being because we empathize.
Action and passion	Every 3-10 pages	When stuck in difficult situations, the reader knows that the hero can not die, so she asks herself: how is the hero going to get out of this alive? (Except sometimes, main characters actually die, leaving us in shock). The same applies for romantic scenes, where we wonder not if, but how it's going to work out between two characters.
Story progression	Every 10-30 pages	Right from the start, the authors put under the reader's nose a bunch of questions: what is happening, why is this guy so mysterious, and so on. The reader wants to know the answers, so she keeps reading until answers are provided, along with new mysteries to figure out.

Looking at blockbuster action movies such as The Bourne Ultimatum, the same kind of pacing emerges: action scenes are followed by the protagonist learning about his past. Then the plot moves on, the character meets new people, finds himself new tasks to do, and back to action scenes.

These rewards and pacing also echo those found in games and mentioned in a class on game balance from Ian Schreiber: gains in character power, discovery of new areas, and progression of the story are rewards to be used at irregular intervals to keep the player engaged. So reading books, watching movies, and playing games seem to provide similar rewards.

Dopamine

Let's dig down to the physiological level of rewards. Most of the articles dealing with the physiological response of gaming revolve around addiction. For instance, a 2012 NY Times article reports that Zynga helps addict millions of people to dopamine, a neurochemical that has been shown to be released by pleasurable activities, including video game playing, but also is understood to play a major role in the cycle of addiction.. To that, the Zynga co-founder replies: Given that we're human, we already want dopamine. And that does not calm things down. So let's look at a less controversial topic: the physiological response of reading. This is not a survey of the field, but rather some picks from a few Google searches - nothing very serious.

First, according to Farland, a current writer, the dramatic structure of stories (exposition - action - climax - denouement) matches the bio-feedback of hormones such as dopamine, adrenaline, and cortisol. He says: As a person "hunts" for clues, or for a way out of a problem, the brain rewards the person by releasing dopamine as a reward. [...] When you reach the climax of the novel, [...] you reach the climax of your emotional exercise. When the story ends [...] your stress is released. The adrenaline and cortisol stop flowing.

As notes from a psychology class on stress can tell us, cortisol is the key hormone of stress. Adrenaline is the hormone that tells our body to be alert. And finally, dopamine is in charge of rewarding our brain.

So what happens when we start reading? Some have guessed that we are having pleasure because reading is a tough task, and our brain rewards us for completing such a hard task. This seems confirmed by a 2001 study who showed that transitioning from rest to reading produces the same increase in dopamine concentration as transitioning from rest to memory-intensive tasks (something cognitively demanding). Although, a 2000 study seems to reject this hypothesis. Something that might be worth investing is whether reading a microwave-oven manual generates as much dopamine as reading an exciting short story where the action starts right from the start.

It may actually be more complicated: the dopamine concentration could actually not indicate our pleasure, but our expectation of pleasure: dopamine motivates us, increasing our energy and drive and compelling us to engage in the pleasurable activity. If everything is as nice as the brain predicted, dopamine levels remain elevated. If things turn out even better than the brain hoped, dopamine levels are increased; we engage in the pleasurable activity even more vigorously. If, on the other hand, the activity is less pleasurable than we thought it would be, dopamine levels plummet.

Back to games

So, what can we conclude about games? First, much like movies and books, reward us by generating dopamine when we succeed at a difficult cognitive tasks such as a head-shot in an FPS, or a successful Chess trap. That is pretty close to fiero, and in fact, Bateman already suggested in 2008 that fiero is a cocktail of epinephrine and dopamine. So, nothing brand new here.

Perhaps more interesting, long-term enjoyment seems to require the dopamine to yo-yo - which is bad. Let us assume that our brain produces dopamine by expecting a nice event. Then when our brain is done with those nice events, the dopamine level will decrease. That would be a horrible yo-yo if there were only one kind of event, but books, movies, and games, have at least three: action, story, and character events. So alternating events and interweaving them in such a way that our brain is always on the lookout may keep dopamine, and pleasure, at high levels instead of making it yo-yo.

There might be a few gotchas, though. First, the magnitude and the lifespan of the dopamine burst depends on a lot factors. Grinding monsters for a drop is only pleasurable so long as the brain is expecting that item to drop. After a couple days, the dopamine is all gone, and it's just boring. Some studies should investigate the average magnitude of an "achievement unlocked!", or the lifespan of a boss kill or a level up.

Second, dopamine bursts may not stack. The brain may be too busy expecting a story progression event that it may ignore, or even worse, be displeased, by a character progression event: it was not expecting it! This limitation does not seem cognitive, but rather emotional, so maybe people with higher EI could stack expectations and dopamine bursts more easily than indifferent people who say "it's just a game"?

Third, and to finish as we started, with books: Stephenson and Martin alternate their character viewpoints chapter after chapter, possibly to keep the reader's attention. By the way, they rarely handle more than 7 characters at the same time, since 7 is a magic cognitive number. These changes in views often cut short the action, so the reader may get frustrated, or even vexed for being tricked to continue reading by the exact same three mechanisms every chapter. It is interesting to know why people keep reading those long books, but that last reason is exactly why I stopped.

Quests - Howard 2008

Quests: Design, Theory, and History in Games and Narratives by Jeff Howard, in 2008.

History of quest games

Year	Game	Innovations
1974	DnD	GM as referee, quests taken from Celtic, Norse, and Arthurian mythologies.
1976	Adventure	on computer, first RPG, network play
1983	King's Quest series	cut scenes, music, multiple endings, optional puzzles, and side-quests.
1985	Ultima IV series	virtues, colors, and classes are related
1986	Zelda series	quest status screen shows the player's progress, first action-adventure game.
1999	EQ	proliferating tasks rather than a single main quest
2004	WoW	lore quests, the never-ending war theme is a bleak scenario not particularly conductive to meaningful gameplay: failing a quest is not problematic.

Intro

Campbell's "Hero's Journey" consists of separation, initiation, and return. The individual builds himself, as found in medieval romances. In games, the initiation phase is lengthened and repeated, since it has most action.

A quest is an action that is meaningful to a player. It's also called a "mission" in games with a modern setting.

Ludologically, a quest has goals and consists of searching a functional meaning: a key opens a door, therefore the player should look for a door. A sword kills monsters, therefore the player is expecting to encounter enemies soon. Once meaning is found, the quest is over.

Narratologically, a quest has a story. The story and the lore motivate and immerse the player in the task.

But actually, meaningful quests come from striking a balance between too much action and too much narrative, while keeping in mind the big picture of the game's meaning. Except for XP and loot, why is that quest important to the player? What satisfaction does the player get by doing that quest? Here are some clues:

• Impact on the world: achievement, gaining power, learning about the lore, altering political or moral balance, or changing relationships with NPCs
• Back story: motivation to learn what happened before or what is going to happen after the quest is over.
• Lore: themes and ideas encoded within the world, such as religion, politics, landscape, objects, or challenges. "The world itself is the puzzle", and the player shows his opinions by playing the game.

Symbols should be tied to game mechanics. For example, in Ultima, completing a quest requires understanding the world's allegorical meanings: some colors are associated to a class and a quality (red = warrior = valor). Obtaining a part of a relic should open a door or provide a new power

In the end, the player may quest to make the plot progress, improve his avatar, or to try out fun gameplay. Ideally, a quest should combine the three, but it gets tricky in games where the player is allowed to pursue quests in the order he wants.

Spaces

Both macro and micro levels should guide the player towards the general direction to go to. Both should create a sense of progression and convey a meaning by their layout.

Micro level: balancing exploration and challenge. Tiered spaces such as towers or crypts are easy to navigate: traveling towards the highest or lowest level ensures challenges and rewards. Mazes with a sort of structure also work. There should also be disorientation elements such as traps, secret doors, or dead-ends, as well as obstacles standing between the player and his goal.

Macro level: quest hubs. Hubs are known and relatively safe places such as cities or campgrounds where the player is given quests and has to return to complete them. Hubs are surrounded by several quest locations. WoW has breadcrumb quests to encourage exploration, but no main quest; that makes the world seem disconnected and episodic. See the Morrowind map: the player starts on the periphery of the world, and travels clockwise from hub to hub until Ghostgate at the center of the map for the final encounter.

Dreams within games create initiatory spaces: the avatar can be changed into an animal, a ghost, or an older self, but remains controlled by the player, increasing the sense of immersion in the non-dream game world.

Characters

Cf Propp's dramatis personae at the beginning of theater scripts: characters are not defined by their traits, but by their actions: villain, donor, helper, or hero.

Dialog: keep it short, and let players have choices. yes/no selections are too simple: add a reason to add meaning. Example: NPC says "Take this money as a reward to save my kids". Player should not simply be given "OK", or "accept"/"refuse", but rather "I don't need money to save kids" (which shifts the player's alignment to lawful good) or "You don't have to give me the money - I'm going to kill you myself" (evil, and eventually summons the guards).

One quest per NPC is rare in modern RPGs.

Quest types

Name	Description
fetch	find an object and return it to an NPC
delivery	give an object to an NPC
dungeon crawl	go to certain points of a dungeon - and get loot on the way
escort/protect	usually an NPC, but could be a fellow player too
kill/combat	the most loaded with meaning: killing a peasant is very different from killing a demon. Opponents have to be obstacles to the plot

Objects

Most objects that the player collects are useless (sold to NPCs for money) or functional (healing potion, armor). But certain objects can motivate quests if they are:

• needed but missing,
• loaded with symbols,
• relatively powerful,
• fun to use (eg cast a random skill),
• with a distinct appearance (eg the Tatoos of Planescape Torment)

Sometimes, these objects only are MacGuffins: they are unimportant in themselves but motivate and unfold the plot.

The rod of seven parts: make a story from the whole and powerful artifact, break it apart, and spread the pieces around the world. The story follows naturally, and the players discover the meaning of the quest gradually. It also encourages exploration. Micro-level example: the 3-headed flail from the De'Arnise Hold in Baldur's Gate 2 requires the player to fully investigate the whole castle, and not just go directly to the boss.

There are varieties of ways the player can get an object: looted, forged, stolen, summoned by a sacrifice, or found in a chest at the bottom of a cave. But the way the player gets in possession of an object should give clues about using that object. Examples: a mace loot from a giant should require lots of strength. Frostmourne, given by the Lich King to trick Arthas the paladin, is obviously cursed.

Challenges

Tie the quest presentation to the world map and the log book. The logs of completed quests must give clues about the next quests or where to find them.

Conflicting goals make interesting choices. For example, in Ultima IV, the avatar gains compassion points by not killing 'good' characters, and gain valor points by never backing down from a fight. Interesting choice arises when the player is attacked by a 'good' character. [But what the player chooses (ie the player's opinion) differs from why he was given the choice in the first place (ie the meaning of the game).]

See also: hero's journey.

Fundamentals of Game Design, ch 15: RPG

Inventory can be:

• a grid where player can position items in empty cells, like in Diablo 1 or 2
• one ore more simple list(s) of items, with an eventually limited number of slots, like Pokemon's backpack
• items have weight, and the inventory is limited to a certain weight, like in Baldur's Gate

Functional character attributes = characterization attributes (stats: DEX, STR, INT, ... skills that change unfrequently, a class system pushes players to specialize) + status attributes (XP, different classes can have different amount of XP required per level (e.g. Baldur's Gate), but players should know it when they pick their character).

Instead of having levels giving sudden bonus, we could have no levels and stats would increase directly proportionally to the XP. After all, levels harm immersion. However, levels add achievement goals and let players spend regularly newly-acquired points in skills they choose.

Skills

Spells can cost mana/SP, or they could just disappear from caster's memory until she sleeps (a la Baldur's Gate/DnD). Unpracticed skills could gradually decline in efficiency, while frequently used skills could get "mastery" bonuses (like for WoW's crafting skills). Or the opposite: frequently used skills could eventually wear out of power.

Skills can be learned right away when levelling up, or when a skill point is spent in them, or the skill could be obtained from an NPC ("training" with masters), or from other players/NPC by watching them do the skill (e.g. the creature in Black and White learns spells after they have been performed a few times in front of it).

If a character has 10% chance to unlock a door independently of the previous tries, then the player will try until the lock eventually opens. Then the 10% chance only slows down and annoys the player. Instead, the better at unlocking doors the character is, the faster the door will be opened. If the lock is too complicated for the character's unlocking skills, then the door unlocking progression bar simply does not increase.

Stories and quests

If the overall story is "save the world", then give meaningful reasons why the character would be ready to do side-quests like delivery boy. Good example: helping a hermit to find his lost dog because the collar hides a key to an important door that the player needs to take. Bad example: helping a hermit simply to get XP, or just to help him out by pure generosity (but really, players are not solving NPC problems by pure generosity).

Anyway, stop writing stories about saving the world.

[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.