作者：Chris Grey

尽管随机性能够用于影响玩家的游戏体验，但却很少人真的花心思去创造随机性。我们都曾遇到过有关稀有随机掉落道具的战争故事，而我们也需要花很多时间才能获得它们。更糟糕的是那些一下子便得到这种稀有道具的玩家还对社区中的其他玩家炫耀，就好像他们能够控制随机数生成器一样。不管会变得更好还是更糟，如今的随机性能够有效地丰富玩家的游戏体验；如此我们为何不说说该如何更积极地创造随机性？

而今天，我想侧重于讨论掉落道具，也就是我想说说在《双重国度》）中，玩家击败怪物以及在驯服怪物过程中所获得的掉落道具。我将避免提供简单的数字；相反地，我会呈献给玩家一些有关随机感的启发法。

ni-no-kuni(from ramblingofagamer)

首先，让我们着眼于当前其他设计师所使用的方法。一般情况下设计师都会着眼于道具在游戏内部的经济价值，并决定它的稀缺度。越强大的道具将越晚出现，或者带有更低的常数比例。我们需要让玩家能够在获得道具时产生成就感，或至少觉得自己足够幸运。不管怎样，这都能让玩家更加重视道具。如果玩家能在平均尝试次数后获得掉落道具，并且设计师也准确设定了道具的价值，那么玩家便能够感受到这一价值，并更紧密地依附于道具上。

基于恒定的掉落比例，以下是关于农场体验的图表。你可能期待看到钟形曲线，但是我想在此列举其它包含于该数据中的内容。而为了做到这一点，我们将改变垂直轴以呈现出如下内容：假设你的玩家在获得其中一个道具再杀死敌人，那么以下便是关于玩家会持续农务多长时间。

population of players still farming for their first drop over time（from gamasutra）

让我们注意形状；在此我们需要注意的一个关键点便是曲线永远都不会真正到达0点。这便意味着有些玩家从未真正成功获得道具，而他们将更加辛苦地经营农场，因为他们需要投入大量时间去执行设计师所规划的，即要求他们在五分之一时间内完成的任务。甚至玩家在获得掉落道具时所拥有的好心情也会在这一关卡中被摧毁。更糟糕的是，使用这些道具而执行农务的过程中会歪曲玩家对道具的价值观‘即大多数玩家在看到别人无需投入大量时间去刷任务时便会产生不公平感，并且他们将把这种怨恨发泄在道具中。自然地，这种怨恨也会溢出游戏，而玩家也将大肆发泄游戏的不公平。这些玩家将被任务的属性给垦殖殆尽，而这也将破坏设计师们精心设计的难度曲线。如此的受挫将导致玩家退出游戏，如果玩家已经投入了极大的精力于游戏中并坚持了很长一段时间，那便说明你疏远了这些富有激情的玩家。如果从游戏全局来看，这些对于随机掉落道具的愤怒也就没那么重要了。

在这种情况下使用平均值去达到平衡将会引起各种各样的问题。在图表中，我们注意到6%的玩家会在尝试平均值出现前获得掉落道具，而一半的玩家在平均值出现前便拥有了道具。这便意味着大多数玩家不会满足设计师的设计目的而多次面对事件，实际上，任何玩家通常只会经历一次这一过程去获得任何一种掉落道具，这将成为玩家对体验持续时间的共识。也许这只是一个快乐的错误，但是它却有可能减少设计师希望玩家所获得的努力感。我们预测将会有25%的玩家花费多于平均值1.5倍的时间去争取掉落道具，而超过10%的的玩家将花费平均值2倍以上的时间去获得道具。如果这些玩家着眼于剩下的玩家群体，他们将会发现自己的体验在游戏过程中所占时间比例是运气元素的2至3倍。

当50%的玩家在早期完成刷任务而25%的玩家是在游戏末尾时，带有稳定资源的设计师将受到吸引去创造平均体验。此外，这些25%的玩家将开始着眼于活动所带有的缺点。如果设计师忽视了尾端的游戏体验并拥有一些不同的掉落道具要求，那么他们便很难迎合所有玩家的喜好；当玩家需要更多掉落道具，他们更有可能坚持到游戏最后。由于专注于数字上的平均体验，设计师其实忽视了任何一种掉落道具上75%的玩家。

其它类型的随机性–不断增加的掉落道具

我想要呈现出两种简单的选择。首先便是掉落比例的提升。每次当玩家不能在事件最后获得掉落道具时，那么该道具下次掉落的可能性便会大大提升。这种可能性将在以设定好的掉落道具上进行叠加，即当道具掉落时，可能性将重置到其它关卡上。而如果你希望游戏中只有一种掉落道具的话也可以将其重置为0；如果你希望让玩家在游戏体验中花相同的时间而获得另一种道具，你也可以将其重置为初始概率；如果你希望此时的道具更有价值而在之后更容易找到，你可以将其重置为较高的可能性。

以下是关于这种体验的新图表。

escalating drop rate（from gamasutra）

这次我们会注意到曲线在最右端已经触及0点了。如此便消除了我们之前所提到的无底的体验。当然也会出现一些运气欠佳的玩家，但是关于他们用于面对这种不幸的时间也存在着上限。这里仍是一些关于战争的故事，但是如果设计得当的话，设计师便能够更轻松地设计出最高的玩家体验，并且将更加靠近平均值。如此那些战争故事便能够有效地加强玩家体验，而玩家不仅能够感受到自己的努力，并且这种感受也不会超过设计师的预期，并且能够有效地带给玩家骄傲感。而玩家想要获得某一道具的焦虑感也将被填平。

此外，如果你最初所设置的掉落比例较低，并且让增长率能够不断提升，你将拥有更少的幸运玩家。如果你希望玩家能够通过反复争取强大道具而精通具有挑战性的战斗的话，这种设置便很有帮助。但是需要注意的是，那些在首次尝试便获得道具的玩家将扭曲他们的难度曲线，尽管这种情况比玩家进行多次尝试更加微妙。授权并不是件坏事，但是这将导致幸运的玩家觉得游戏很容易被战胜（因为一些偶然元素）。一般情况下，不断提升的掉落比例将让任何特定玩家的游戏体验更加均衡，并且对于他们来说这种变化是相对无形的。

这里存在着一种观点，即如果玩家在获得道具前射死一些相同类型的怪物会出现什么情况。如果玩家清楚发生什么了，并知道他们在获得一个掉落道具前需要进行多次战斗，那么战斗可能就会突然变得有效了。而因为任何回报都是隐藏在转角处，所以这种形式的投机也会更加有用。我们不能低估这种推动力量的强大性。强迫玩家重复做一件事50次是多么烦人啊，因为失去了最初的新鲜感后，所有的体验对玩家来说都没有了乐趣。如果游戏能让玩家在经历任何一次尝试后随机获得奖励，那么玩家便会对游戏更有兴趣。如果玩家觉得自己所付出的能够随时得到回报，而不是寄托于未来的某一时刻，那么他们便会更加重视游戏体验。

其它类型的随机性–收获递减

这与上述的随机性完全相反。这一理念是关于玩家拥有有限的机会在道具消失前把握住它。一般情况下，关于掉落道具的最初可能性都比较高，并会随着玩家每次的失败而降低，或者在玩家进行一系列尝试后事件将会消失。而不管是何种情况都会让玩家在经过几次尝试后而更加难以获得掉落道具。

这种随机性并不像我们在保证玩家基础将永远不会获得道具那样简单。比起传统方法而言，这更加人道化，并且玩家将不能以时间去交换游戏内部的价值。如果道具对于玩家来说具有很大的价值，那么玩家便会知道其中的风险，即最终结果将具有很大的紧迫性，而拥有技能的设计师便能使用这种方法去创造更大的情感标志。

关于这种类型的掉落道具存在着一种潜规则。基于permadeath机制，玩家仍然会因为结果而紧张，并能够使用加载功能而进行多次尝试去获得自己想要的掉落工具。如果游戏删除了重新加载功能，就像在《恶魔之魂》中那样，那么你便会考虑缩短游戏长度（但仍具有重完价值），或者设置不同的掉落工具，并且只有一种道具在游戏中是可得到的。如此设置将推动玩家基于他们所获得的道具而调整游戏风格。我们必须注意这种随机性，因为它很容易惹怒玩家。你已经非常接近于大多数玩家的核心期待：“我主导着这个游戏世界，并且因为付出了努力，所以我必须能够得到一切想要的。”

一些通用的启发法

因为大多数人都不知道如何看待可能性，所以我想要列举一些指南。

当你感到疑惑时，可以创造一个模拟对象。当你使用任何类型的可能性分布（除了恒定的掉落比例），你并不需要罗列出所有例子的数字试验。我更建议你们写下一个程序（游戏邦注：或者邀请程序员好友的帮忙）去模拟效果，并生成系统发展（经过多次测试后）的图表。这些信息非常有帮助（虽然不能百分百保证是准确的），并且我们也无需投入大量时间进行计算（要求获得准确答案）。

一般而言，玩家所面对的掉落道具越随机，他们的整体体验将越接近平均体验，并且他们将越有可能需要面对最糟糕的短期情况。让我们着眼于这种方法：如果每个人摇50次骰子，那么骰子所滚动的总数将不会有太大的区别，而每个人也至少滚动了几次。但是这里存在着一个很狡猾的陷阱：你不能假设运气欠佳只会影响着某些玩家；这几乎会打击到所有玩家。所以请谨慎地设计。

反面情况也是真的。即游戏中的少量随机掉落道具意味着玩家体验将非常不平衡，并且具有很大的差别。

人们总是不愿意去估算各种可能性。可能性越低就意味着估算能力越糟糕。特别是在面对稀有掉落道具时，这种情况便更加明显；如果玩家知道掉落道具是稀有的，他们便会感受到满满的压力。除此之外，当玩家需要面临较长的农务过程时，他们便会感受到消极情绪，而幸运的玩家在经历短暂的收获道具喜悦后将能够更快速地前进。

人们总是会将运气与技能结合在一起。调查能够强化这种情况的机制很有趣：为技能型玩家提高道具掉落比例将让他们能够继续尝试一些更有趣的内容，而让低技能的玩家能够获得各种道具却带有风险性。这种情况是我很少看到的，但是我却认为它具有很大的潜能。

一般情况下随机性是讨喜的，如果玩家买进一些带有风险性的内容，那么我们便可以使用投机去创造惊人的情感体验。遗憾的是，因为游戏机制背后一些额外的可能性将创造出各种不同的体验（来自任何玩家或者玩家间的游戏过程转变），所以最接近我们想法的内容总是未能得到理解。随机性具有巨大的潜能，而我只能通过文本去描述一些皮毛，所以我建议你们还是通过试验去深入摸索。

（本文为游戏邦/gamerboom.com编译，拒绝任何不保留版权的转载，如需转载请联系：游戏邦）

Emotions and Randomness – Loot Drops

by Chris Grey

Even though randomness can be used to greatly influence a player’s experience with a game, I haven’t seen many people put much thought into crafting it. We’ve all got war stories about a rare drop that took us hours to get, if not tens of hours. Gamefaqs is loaded with forum threads talking about the despair of the random drop. Even worse are the threads made by people who got the drop in one go, bragging and taunting the rest of the community, as if luck with the random number generator were something they actively controlled. For better or worse, randomness currently colors the play experience tremendously; why not talk about crafting it more actively from our side so that these experiences are less accidental?

Today, I’d like to focus on drops. I’m being a bit loose with the word because I’d like the ability to talk about both items dropped by defeated monsters and the monster taming process in Ni No Kuni, where enemies randomly become recruitable after you beat them up. I’m going to avoid giving hard numbers wherever possible; my aim here is to give a few heuristics about how randomness feels to the player.

First, let’s look at the way it’s done now. Typically, designers look at the in-game economic value of an item and decide how scarce it should be. More powerful items either appear later in the game or drop with a much lower constant percentage chance. The idea here is that players should feel some kind of sense of accomplishment when they obtain the item, or at least see how lucky they’ve been. Either way, it’ll bring the players to value the item, hopefully in accord with the designer. If players manage to get the drop in the average number of tries, if the designer has valued the item correctly, the player will typically have a similar valuation of and appropriate attachment to the item.

With a constant drop rate, here’s the graph that captures the farming experience. You might be expecting a bell curve here, but I want to illustrate something else born from this data. To do so, we’re going to change the vertical axis to reflect the following: assuming your players kill enemies until they get one of the items, here’s how long the player population will be farming.

Pay attention to the shape; the key point to notice here is that the graph never actually hits zero. That means some of your players are never going to successfully acquire the item, and they will have a terrible time trying to farm it because they will spend tremendous amounts of time doing a task the designer had only pictured them doing for a fifth of that time. Even the good feeling at getting the drop if they eventually manage to get it is generally overshadowed at this level. What’s worse, the time farming the item will skew a player’s value of it; most players will resent having to grind a massive amount of time if others did not have to, and they will focus their resentment on the item in question. Naturally, this resentment will also spill over to the game, and they will undoubtedly vent about how unfair the game is to anyone that will listen. These players will be overfarmed by the nature of the task, and this also ruins the otherwise carefully crafted difficulty curve. Their frustration can lead to quitting the game, and if this player was dedicated enough to stick it out that long, you probably alienated an incredibly passionate player. All this angst for a random drop that probably didn’t matter much in the bigger picture of the game.

…and the Queen save the poor souls who feel compelled to get the collect all random drops achievement. That synergy can quickly lead to tens of hours of despair and compulsion, if there are many items or especially rare items.

The problem with using averages to balance in this case is myriad. In the graph, notice that about sixty percent of players will receive the drop before the average number of attempts, and half of the population gets the item significantly before the average. This means most players won’t be seeing the event as many times as the designer probably designed for, and in reality, as any one player usually only goes through this process to get any one drop once, this will become the general consensus on how long the experience takes. Potentially a happy mistake, but it does diminish the feeling of effort the designer probably wanted the most players to feel. Of the rest, it can be expected that about twenty-five percent of players will take more than one and a half times the average to get the drop, and more than ten percent will take more than twice as long as average. If these players look to the rest of the player population, they will see their experience taking more than two to three times as long as the lucky half, respectively.

A designer with fixed resources would be drawn to craft the average experience when, in all honestly, it’s the fifty percent who finished significantly early and the twenty-five percent on the tail that need the attention more. Additionally, the latter will be the ones to really begin to see the activity for the warts it has. If the designer neglects the tail experience and has several different drops required or encouraged in game, the designer will eventually fail all of their players; the more drops the player needs, the more likely that the player will be in that tail at some point in the game. By focusing on the mathematical average experience, the designer is effectively neglecting seventy-five percent of their players on any single drop.

Other Kinds of Randomness – Escalating Drops

I want to present two simple alternatives. The first is an escalating drop rate. Each time a player fails to get the drop at the end of the event, the probability it drops next time increases. This probability caps at a guaranteed drop, and once the item drops, the probability resets to some level. It can reset at zero if you only ever want one in the game; it can reset at the initial probability if you want to make the experience to get another item take the same amount of time, more or less, as the first time; it can reset at a high probability if you want the item to be valuable now but easy to come by later.

Here is the new chart for this experience.

Notice how the line now hits zero on the right of the graph. It eliminates the abysmal experience we spoke of above. There will be unlucky players, but there’s a cap on the amount of time they’ll have to spend with their misfortune. There will still be war stories, but if designed well, the worst-case player experience can be designed for more easily, as it will more closely match the average. This can lead to those war stories that can enhance the player experience, as they feel like they struggled, but not much harder than the designer expected, which is nice way to give a bit of fiero. The angst of trying to get the item will always be fulfilled.

Additionally, if you set the initial drop rate low and let the growth rate accelerate, you’ll have fewer lucky people as well. This could help if you want to make the player master a challenging fight through repeated attempts to potentially get a powerful item. It’s worth noting that the player who gets the item on the first try will have their difficulty curve distorted, even though this case tends to be more subtle than the player who takes many tries. Empowerment is not a bad thing, but it can lead the lucky player to think the game is much easier than it is because of a fortuitous break. In general, the escalating drop approach will make the experience a little more uniform for any given player, and usually, it will be relatively invisible to them.

There’s a temptation here to wonder what would happen if you had to kill several of the same kind of monster before the item could even become available. If the player understands what’s happening, and they know that they will be fighting several times before they could even get a drop, that fighting suddenly becomes work. Gambling in this form works because the payoff is potentially always right around the corner. It cannot be understated how powerful this force is to motivate. Asking someone to do something fifty times makes it a chore, and times ten through forty will not be savored because after the initial novelty of doing it, you know it will not net reward any time soon. If a task could be rewarded randomly after any one attempt, more attention to detail and care will go into it from the player. The player will appreciate the experience more if they feel like what they are doing could pay off at any moment, not just some long time in the future.

Other Kinds of Randomness – Diminishing Returns

This is the invert of above. The idea is that the player has a limited number of chances to get an item in game before it goes away completely. Typically, the initial probability of the drop will start high, and either decrease with each failure, or the event will disappear after a set number of attempts. Either way makes the drop impossible to get after a certain number of chances.

This randomness is tricky to deal with as you are, in no uncertain terms, guaranteeing that a percentage of your player base will never get the item. It can be more humane than the traditional way as you are giving no option to exchange time (farm) for in-game value. If the item has significant value to the player, and the player knows the stakes, there will generally be a significant amount of urgency put on the outcomes, and a skilled designer could use this as a way to make a large emotional mark.

There is an unspoken rule with these kinds of drops. They can be gamed by reloading. As with permadeath mechanics, players can still get some tension from the outcome while using the load function to try as many times as they want to obtain the drop. If the ability to reload is removed, as it was in Demon’s Souls, then you may want to consider making the game short, but replayable, or having several different drops, only one achievable in the game. This can force players to actually have to adjust their playstyle based on what they got. Be careful with this kind of randomness, as it can easily inspire rage. You are very close to a core expectation of most players: “I am master of this game world, and given effort, I should not be deprived of anything I want.”

Some General Heuristics

Since most people aren’t taught well to think about probability, I wanted to give a few guidelines to work with.

When in doubt, make a simulation. When you use any type of probability distribution besides the constant percentage drop, you do not need to do a full mathematical workout of all cases. I highly recommend writing a program (or bribing your friend the coder to do so) to simulate the effects and generate graphs of how the system behaves when tested a huge number of times. That information, while not guaranteed to be exactly right, will be good enough, and the calculations required to get an exact answer are not worth the time required to compute them in most cases.

Generally speaking, the more random drops the player is compelled to farm, the closer their total experience will be to the average experience overall, and the more likely they are to face the worst case short term scenario sometime in their experience. Look at it this way: if everyone rolls fifty dice, it’s likely that the roll totals won’t differ much, and everyone will have probably rolled at least a couple of ones. The trap here is subtle: you cannot assume that poor luck will only affect some players in this case; it is almost guaranteed to strike everyone. Design accordingly.

The reverse of this is true, too. A small number of random drops in your game will mean that the player experience will be very uneven and different from person to person.

People tend to be terrible at estimating probabilities in their head, and dry spells leave bigger scars than lucky breaks feel good. The lower the probability, the worse the estimation ability. This can manifest especially with rare drops; people tend to start becoming frustrated long before the average if they know the drop is rare going into the session. Additionally, people will typically experience negative emotion for a significant portion of a farming session they consider to be long, while players who get lucky tend to move on quickly after experiencing the short-lived joy over a drop.

People conflate luck and skill quite often. It might be interesting to investigate mechanics that would reinforce this: increased drops for skilled play would allow those who have already mastered what the game is teaching to move on to something more interesting to them, while giving the less skilled players a way to both potentially improve and still get whatever item is at stake. This is something I’ve rarely seen, but I think would have huge potential.

Randomness is lovely, and if players buy into what is at stake, gambling can be used to craft incredible emotional experiences. It’s a shame that something so close to our hearts is so ill-understood because a little extra crafting of the probabilities behind the game mechanics could yield incredibly diverse experiences, both from game session to game session for any one player and between players. There is an amazing amount of potential, and I was only able to scratch the surface with a huge amount of text so all I can recommend for those who are willing to is: experiment.

As I didn’t get to show examples this time, I’m splitting them off into another entry. When it is done, I’ll link to it here.(source:gamasutra)