作者：Raphael Koster

近期，我花了大量时间来思考趣味性的本质。我将其弱化成一种认知挑战，我的看法如下：趣味性是你在运用大脑解决认知谜题时获得的感觉。谜题有时来自于电脑，有时来自于其他玩家，但无论来源于何处，从根本上来说你的大脑都在努力感知其样式。成功识别样式后正确地执行了某些该样式没有明确说明的动作，这样便产生了胜利感。对此进行更深入的思考，同游戏设计这种艺术形式联系起来，我将在下文阐述的就是自己的“趣味性理论”。

上述发现预示，或许我们可以通过某些方法来分解或分析某个谜题或挑战显得有趣的原因。现在，挑战或谜题的形式多种多样，比如像俄罗斯方块那样的时空挑战和像足球那样的体能灵敏度挑战。这些挑战之间有什么共同点呢？

构建子游戏原子

以下运算法则来源于尝试将MMOG战斗系统的基本特征融入到MMOG的交易技能中，后者向来被认为不够有趣。有趣的是，MMO战斗本身也往往被认为不够有趣，但是在正确执行的情况下却能成功地吸引玩家长达数个月时间。

成功的MMO可能需要包含许多独立子游戏（游戏邦注：战斗便是其中之一），要产生最大化的影响力，每个子游戏都需要满足所有以下要求。事实上，原子需要拥有某些已知的“系统输入”和“系统输出”，这两者的紧密结合才能构建起游戏“分子”。

通常情况下，我们将游戏设计中的每个“游戏系统”视为原子。当你用许多原子组成分子时，这个分子整体也必须满足让原子有趣的所有标准。纵观互动娱乐产品，至少包含一个原子，有些可能包含多个分子，比如MMOG。最后，我们所说的“游戏范围”衡量的就是游戏所拥有的原子数量。

以MMOG战斗为例

我选择劈砍型的MMO战斗为例，因为这是个根深蒂固的机制，已经历经二十多年的润色。这是个多人机制，给协作性游戏带来额外的亮点。它的对象可以是电脑中的对手或其他玩家。通常来说，它本身并不能被视为完整的游戏，只是MMO众多系统之一，因而带有游戏原子的递归性和连接性。

解析MMOG战斗娱乐性后，你会发现其拥有大量的必须元素：

准备是必须元素。多数情况下，这或许仅仅是在进入遭遇战之前先回满生命值。最好的情况是，游戏可以通过对非战斗角色的需求将战斗系统同更大的子游戏网络联系起来。最少，应当允许玩家进行不同形式的准备工作，以提供不同的战术选择。

重点：准备不可凌驾于技能之上。事实上，在纯粹测试技能的游戏中，你或许不会有许多准备选择。应当注意的是，在这种情况下，高级玩家可能会故意选择在准备不充分的前提下面对挑战，比如反向玩DDR、在象棋中给自己制造困境或在硬核模式下玩《暗黑破坏神》。

位置感是必须元素。位置影响遭遇战的战术和战略。换句话说，位置会影响到风险和奖励。

重点：去除位置的影响是件很简单的事情，但这样最只会让战斗显得很乏味。但是，如果位置能够对遭遇战产生影响，那么会使游戏质量大幅提升。

稳定的核心机制。这是待解决谜题的本质，是决定可以呈现何种内容的规则，从本质上来说这是有趣的。实际上，这个核心机制本身或许就可以被视为原子。

重点：应当注意的是，如果只有核心机制，那么只能在有限的时间内让玩家觉得有趣。

一系列挑战。这是内容，每个敌人都是个独特的谜题。那么，敌人的结合也能够产生出更多的谜题类型。

重点：如果可以采用与战胜之前敌人相同的战术来打败新的敌人，那么新的敌人就不算是游戏的新挑战。玩家所说的重复性便是这种情况。

解决遭遇战所需的一系列能力。我们设计任何角色都不拥有应对遭遇战需要的所有能力，这样就可以促使玩家通过团队合作来解决问题。即便在单人游戏中，只依靠单种能力的玩家往往最终无法在高级遭遇战中获得胜利。

重点：通常情况下，这种元素在较低挑战遭遇战中并不突出。当你遇到更为复杂的遭遇战时，其必要性逐渐凸显。

使用能力的技能是必须元素。不当的选择会导致遭遇战的失败。事实上，这种技能包括多种类型：遭遇战期间的资源管理；时机的掌握；体能灵敏度；对动作中所有变量的检测。

重点：这与战斗前的准备并无关联，因为其完全不涉及技能方面的问题。技能较高和较低玩家之间的差别应当在于游戏体验上，其他的东西应当完全相同。否则，玩家会认为自己只需要让游戏自动战斗即可。

应当有可变的反馈系统。遭遇战的结果应当是完全不可预测的。理想情况下，玩家技能越高，在遭遇战后获得的奖励应当越好，还需要通过奖励变化性来保持玩家的兴趣。

重点：仅仅使用随机掉落系统是不够的，这很容易导致玩家需要等待很长时间才能获得想要的东西。反馈应当总是有一定价值，但受益的对象可能不是玩家，或者将系统设置为根据遭遇战的应对情况来提供反馈（游戏邦注：比如战利品）。奖励应当同游戏挑战间存在因果关系。

必须考虑到精通问题。系统不允许高等级玩家从低挑战遭遇战中获得最大的利益。上述情况会产生不利影响，可能导致低等级玩家无法接触到游戏内容。

重点：唯一的有效方法是，设计低等级内容对高等级玩家不再有吸引力（游戏邦注：或者完全毫无用处）。

失败需要付出代价。遭遇战或挑战的失败会导致你完全无法获得战利品，下次再次尝试挑战时需要从新开始。

重点：你在下次尝试挑战前，可能会改变前期的准备。你面对的挑战不一定需要重新设置到最初的状态，可以采取其他的方式。设置失败惩罚可以扩展游戏中的挑战。

构建原子简图

所有这些元素都可以被运用到任何游戏系统中，但我们仍需要从理论中进行深入的分析。以下是分解后得出的必须元素：

1、准备是必须元素。

2、位置感是必须元素。

3、稳定的核心机制。

4、一系列挑战。

5、解决遭遇战所需的一系列能力。

6、使用能力的技能是必须元素。

7、应当有可变的反馈系统。

8、必须考虑到精通问题。

9、失败需要付出代价。

你可以使用这种原子方法，将游戏视为游戏原子的有向图。原子图形如下所示：

在这个图形中，你会注意到能力和技能是平衡的，这是因为如果这种平衡不存在，就会产生精通问题。核心本身成为循环，不断用挑战测试这些能力和技能。应当指出的是，整个核心机制可以被用来组成多个原子。

那么，你可以使用这种方法来绘制游戏图形，看看游戏系统间存在何种关系。一个原子的输入和输出可以连接到另一个原子的输入或输出中，原子之间也会相互嵌套。

这篇文章没有足够的篇幅来讨论MMO的图形，但我们可以以西洋棋为例进行解析。

1、准备阶段通常被略过，因为这是款两人游戏。但是，通常该游戏中的准备形式会对一方造成不利局面。

2、位置是固定的棋盘，尽管可以使用相同的规则制作出其他有趣的棋盘（游戏邦注：比如四人西洋棋棋盘）。

3、“西洋棋”的核心机制是“俘获所有的棋子”。

4、一系列挑战取决于不同的对手。在这种情况下，你可以将西洋棋视为不含有多阶段体验的“简单游戏”。多数桌游属于这个类别，但有些解谜游戏属于例外情况，可能需要在每个关卡前进行准备。

5、解决挑战所需的能力非常有限。你的棋子就放在棋盘上，你只需要移动它们即可。

6、游戏的技能在于选择移动哪个棋子。事实上，这个部分属于另一个游戏原子，因为每次移动本身就是个需要解决的问题：是移动还是跳跃？

7、获得整盘西洋棋游戏比赛胜利的可变反馈完全由你和对手的情感响应驱动。

8、西洋棋游戏并没有试图通过正式机制来解决精通问题。如果你面对的是个新手，你就会获得胜利，这样的游戏对双方来说都显得很无趣。正因为此，我们自己便会刻意避免这种情况的出现。

9、未俘获所有棋子就会导致失败。下次游戏时，你需要重新开始，上盘游戏俘获多少棋子丝毫没有作用。应当注意的是，如果添加评级、排名或胜负记录系统，就会使整个西洋棋游戏原子成为“竞争排名”的游戏。

现在，嵌套在西洋棋游戏中的是另一个原子，即移动棋子并试图俘获对手棋子。

1、准备阶段就是上一次的棋子移动。

2、位置就是由上次移动创造出的特别战术情境。

3、核心机制是“俘获棋子”。

4、挑战在于可能面临你自己的多个棋子被俘获的风险。

5、你的能力系列为斜向移动一个棋子。根据当时的游戏情境，这可能是个王者俘获或普通俘获，可能包含多次跳跃。

6、这个原子中无需技能。这就预示着，你不能在这个原子中嵌套入其他的原子。这是组成西洋棋的最基本原子单位。

7、成功的可变反馈很有趣。可能是直接成功地俘获1枚棋子，可能通过连续跳跃俘获多枚棋子而取得极大的成功，可能未成功俘获棋子但创造出王者俘获的机会，可能是牺牲1枚棋子来为下个原子创造更好的情境。这种多样性正是使西洋棋成为有趣游戏的原因。移除这些动态之一显然会导致游戏质量下降。

8、因为在游戏中移动单个棋子不涉及任何技能，所以不存在精通问题。

9、如果这个原子失败，你在下个回合开始时会面临更糟糕的情境，因为你的对手可以根据你的失误采取行动。

实际应用

以上内容看上去相当理论化，显得毫无用处。如果你使用这个理论来分析制造系统又会如何呢？让我们以多数MMO中的交易技能为例来分析。

1、准备是必须元素。自从《网络创世纪》面世起，我们都是以“收集合适材料”来为制造系统提供趣味性。所以，我们已经在“准备是必要元素”层面上做得很好。但是，理想情况下准备本身应当递归地遵从所有这些规则。总体来说，我们还未做到这点。我们通常也没有完全利用“准备应当有多种形式”这个部分的优势，我们通常设置的是用静态材料制作出静态结果。

2、位置感是必须元素。就今日的制造系统而言，这个层面仍有待挖掘和提升。《星球大战银河篇》在不同位置提供不同的制造优势和劣势方面进行了些许探索，但总体而言仍有待提升。

3、稳定的核心机制。总体而言，我们依赖的还是简单的组合。这个规则本身并不有趣，它将所有的趣味成分都转移到准备上。我们需要像AI在战斗中做出的“反抗”机制。这是制造系统问题的核心所在。目前我们做的还只是在移动单个西洋棋棋子，而不是在玩西洋棋游戏。

4、一系列挑战。简单来说，就是一系列可能的制造物。但是，应当注意到的是，由于稳定的核心机制缺失，系列挑战通常也不会有趣。道具并没有能力或技能让你在制造过程中失败。

5、解决遭遇战所需的一系列能力。从某种程度上说，这点部分实现，但目前多数制造系统不要求玩家间在真正的制造阶段相互配合。他们只需要在收集足够的资源后合成即可。所需要的能力属于准备阶段的一部分，因为制造并没有明确要求拥有何种能力。《Sims Online》中的披萨制作需要多人配合，拥有同样设计的游戏很少。

6、使用能力的技能是必须元素。在多数游戏中，这个部分完全缺失。因为缺乏核心机制，所以没办法使用能力。优秀的核心机制可以提供能力使用的范围，使技巧性地使用能力成为可能。

7、应当有可变的反馈系统。在多数游戏中，这个层面并没有实现。目前，如果制造成功的话，你获得的肯定是你想要的东西。这意味着制造道具比移动西洋棋棋子更加简单，后者可能会产生多种结果。

8、必须考虑到精通问题。这个问题毁灭了多数网络游戏的制造系统，高等级制造者完全封锁了低等级玩家进入市场的机会。

9、失败需要付出代价。这个多数游戏都做到了。

结论

游戏图形可以被视为不规则碎片形。当你绘制游戏图表时，每个可行的技能选择都是个原子，系统由原子间的连接和嵌套构建而成。事实上，整个游戏本身就可以被视为一个原子，无论失败或成功的结果都是“游戏结束”。

如果你得到的原子中毫无技能选择，而且也没有其他原子嵌套其中，那么你在做的根本就不算是设计。如果你得到的原子不符合上述9个元素，那么这个原子可能就不是个有趣的游戏系统，需要重新设计。

这算是趣味性的运算法则吗？不是，但这是检测趣味性是否存在的有效工具。对每个设计出的系统，按照以下问题进行检测：

1、在面对挑战前是否需要做准备？

2、准备阶段是否也能够顺利通过这个问题列表的检测？

3、能否在以不同方式准备的情况下依然获得成功？

4、挑战发生的环境是否会影响挑战？

5、挑战是否有稳定的规则？

6、单个规则是否能够支持多种类型的挑战？

7、玩家能否通过多种能力来应对挑战？

8、在高难度下，玩家是否必须通过多种能力才能战胜挑战？

9、能力的使用是否涉及到技能？如果不涉及到技能的话，这是否是游戏中最基础的动作？

10、是否存在多种克服挑战的胜利状态？

11、高级玩家在面对简单挑战时是否无法获得奖励？

12、失败是否会导致你重新尝试应对挑战？

如果上述问题中有问题的答案是否定的话，那么这个游戏系统可能需要重新设计。（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）

An atomic theory of fun game design

Raphael Koster

Lately, I’ve been spending a lot of time thinking about the nature of fun. I’ve reduced it down to a cognitive challenge, the notion that fun is the feeling you get when you are exercising your brain by solving a cognitive puzzle. Sometimes the puzzle is provided by a computer, sometimes by another player, but either way, your brain is basically trying to perceive a pattern; victory usually comes from identifying the pattern, then correctly executing on some action that the pattern does not account for. For further thoughts on this and its implications for game design as an art form, I refer you to my presentation “A Theory of Fun.”

This suggests that there are probably ways to break down or otherwise analyze what makes a given puzzle or challenge fun. Now, challenges or puzzles come in a very wide array of forms—spatio-temporal challenges like Tetris, and physical dexterity ones like soccer. What do all of these have in common?

Building a subgame atom

The following algorithm came about from attempting to map the basic features of MMOG combat systems onto MMOG tradeskills, which are usually regarded as not having met a sufficiently high bar of fun. Interestingly, MMO combat itself is often not regarded as having reached that bar either, and yet it succeeds in keeping players captivated for many months on end, when correctly executed.

A successful MMO probably needs to have many individual subgames (of which combat may be one) in order to be successful, and for maximum impact, each of them needs to fulfill all of the following requirements. In fact the atom needs to have certain known “system inputs” and “system outputs” so that it can be hooked together to build game “molecules” if you like.

We typically refer to each atom as being “a game system” in game design, but part of the point of this essay is to show that this definition is to a degree recursive. Once you have knitted together several atoms into a molecule, the molecule as a whole must also meet all the criteria for what makes an atom fun. When looking at a piece of interactive entertainment, it is made out of at least one atom, and possibly many molecules, as in the case of MMOGs. In the end, what we refer to as “scope of a game” is really measure of how many atoms it has.

Taking the MMOG combat example

I’ve selected hack ‘n’ slash MMO combat for my example, because it is a well-established mechanic that has undergone twenty years of refinement; it is a multiplayer mechanic, which brings in additional wrinkles for cooperative games that would otherwise be absent from the model; it can be performed either against computer opponents or other players; and it is typically not a full game in itself, but is one system among several in the MMO, thus demonstrating the recursive and connective qualities of game atoms.

When you break down what makes MMOG combat entertaining, there turn out to be a surprising number of required elements:

Preparation is required. In most cases, this may be as simple as healing up before entering the encounter. At its best, there is an opportunity here for hooking the combat system into the larger network of subgames via the need for non-combat roles. At a minimum, different forms of preparation should be viable, in order to provide different tactical choices.

Important point: preparation cannot be allowed to overwhelm skill. In fact, in a game that is a pure test of skill, you may not have variable preparation. It’s worth noting that when this is the case, advanced players will often come to the challenge less prepared on purpose, such as playing DDR backwards, handicapping yourself in chess, or playing Diablo in hardcore mode.

A sense of place is required. Physical location affects tactics during the encounter, and affects the strategy of which locations to have encounters in. In other words, locations affect risk and reward.

Important point: it’s easy to have locations that turn out not to matter, in which case this becomes merely tedious. When they do matter, however, they add immensely.

A solid core mechanic. This is in the nature of a puzzle to solve—it’s a ruleset into which content can be poured, that is intrinsically interesting. Effectively, this core mechanic may be an entire atom in itself.

Important point: Note that by itself, it is probably interesting only for a limited amount of time.

A range of challenges. This is content; each enemy provides a unique puzzle. Combinations of enemies then provide additional puzzle types as well.

Important point: whenever you reach the point where fighting the new enemy can be done using the same tactics as the previous enemy, you have not actually added a new challenge to the game. This is where players find repetition.

A range of abilities required to solve the encounter. We design our encounters such that it takes teamwork to resolve them, via formally preventing any given character from having all the abilities required. Even in single-player games, however, the player who relies on a single ability usually ends up unable to compete at higher levels.

Important point: Usually this starts out not being present at the lowest challenge encounters, and rises in necessity as you reach more complex encounters.

Skill in using the abilities is required. Bad choices lead to failure in the encounter. This skill can be of any sort, really: resource management during the encounter, failures in timing, failures in physical dexterity, failures to monitor all the variables that are in motion.

Important point: This says nothing about the level of preparation in advance of the fight, which leaves out the issue of skill entirely. It should be possible for a skilled and a non-skilled player to have radically different experiences, all other things being the same. Otherwise, players will rightfully say that they could automate the fight.

A variable feedback system should be in place. The result of the encounter should not be completely predictable. Ideally, greater skill in completing the encounter should lead to better rewards, but some degree of variability in the reward is important to maintain interest and minimize “farming.”

Important point: you’re playing with fire here, and if it makes you nervous, this is the only optional item on the list. Merely randomized drops is not sufficient, and it’s incredibly easy to alienate players with long waits for what they want. The feedback should be such that it is always worthwhile, but perhaps not to you—or there should be a system whereby the feedback you get (e.g., the loot) is perhaps tailored to the way that the encounter was resolved. The reward should always be contextual to what the challenge was.

The Mastery Problem must be dealt with. The system cannot permit high level players to derive maximum benefit from less challenging encounters, or you get bottomfeeding. This has the detrimental effect of also closing lower level players out from access to the content.

Important point: the only effective way to do this is to forcibly make the lower level content no longer appeal to (or even be usable by!) higher level players.

Failure has a cost. Loss of the given encounter or challenge ejects you completely from the atom, and pops you out of the stack. Next time you attempt the challenge, you are assumed to come into it from scratch.

Important point: next time you come back, you may be differently prepared. The challenge you faced does not necessarily need to be reset to its original state, as “wear it down” is a viable approach to a given challenge. This leaves open the question of penalties for failure that extend beyond the individual challenge.

Building an atom diagram

All of these things can be applied to any game system, but it requires approaching the issue theoretically. A simple list gives you this breakdown of required elements:

Preparation is required.

A sense of place is required.

A solid core mechanic.

A range of challenges.

A range of abilities required to solve the challenges.

Skill in using the abilities is required.

A variable feedback system should be in place.

The Mastery Problem must be dealt with.

Failure has a cost.

You can, using this atomic method, consider games as directed graphs of game atoms. A given atom looks like this:

In this diagram, you will notice that the abilities and skills are balanced—that is because otherwise, you get the Mastery Problem. The core itself then becomes a loop of repeatedly testing these abilities and skills against those of the challenge. It is worth pointing out that this entire core mechanic may well be composed of multiple atoms itself.

In terms of ludological theory, since atoms “stack,” popping off the top of the stack effectively takes you out of the “magic circle” of privileged space.

You can then diagram games using this method, and see what the relationships are between game systems. Each input and output onto an atom can be linked to the input or output on another atom, and atoms can be nested within one another.

It’s beyond the scope of this little essay to try diagramming an MMO, but even checkers provides an illustrative example.

The preparation step is generally skipped, since this is a two-player game. However, a typical form of prep would be to handicap one side or the other.

The place is a fixed board, though interesting variant boards have been constructed using the exact same ruleset (CheckersFour being one such).

The core mechanic of “checkers” is “capture all pieces.”

The range of challenges lies in different possible opponents. In that sense, you can consider checkers to be a “simple game” in that it is not a multi-stage experience. Most board games are not, but something like a puzzle game, which swaps out the space and perhaps the preparation on every level, certainly is.

The range of abilities to solve this is very limited. You have pieces on the board. You can move them. You can jump with them.

The skill lies in choosing which piece to move with. This part is in fact another game atom, because each move is a problem to solve itself: move, or jump?

The variable feedback of winning the overall game of checkers is entirely driven by your emotional response and that of your opponent.

The overall game of checkers does not attempt to solve the mastery problem via formal mechanics. If you come up against a toddler, you will win. This will make for a dull game for both of you. Because of this, we customarily avoid this sort of match-up.

Failure to capture all the pieces results in loss. Next game, you have to start over from scratch, without any of the captures you achieved last game. All record of achievement is lost. Note that layering on something like a rating system or rankings or win-loss records actually nests the entire game of checkers as an atom within the “climb the ranking ladder” game.

Now, nested within the game of checkers is another atom, that of moving a piece and attempting a capture.

The preparation step is actually that of the previous moves.

The place is the specific tactical situation created by the previous moves.

The core mechanic is “capture a piece.”

The challenge lies in the risk of capture of multiple of your pieces.

Your range of abilities involve moving one piece diagonally. Depending on the game situation, that may be a king capture or a regular checker capture, and it might include multiple jumps.

There is no skill required in this atom. This is an indicator that you cannot nest another atom within this one. It is a fundamental atomic unit of checkers.

The variable feedback for success is interesting. There’s the direct success of capturing one piece, there’s extreme success of capturing multiple pieces via a chain of jumps, there’s the orthogonal success of failing to capture a piece but instead creating a king, and there’s the Pyrrhic victory of sacrificing a piece in order to create a better landscape in the next iteration of the atom. This variety is what makes checkers an interesting game. Removing one of these dynamics would make the game significantly poorer.

Since there is no skill involved in the game of moving a single piece, there is no mastery problem.

Failure ejects from the atom, and next turn you start on a new landscape that is worse off than the one you just left (because your opponent gets to move).

Practical applications

All the above sounds very theoretical and useless. What happens when you walk through a crafting system using this? Let’s look at what we do with tradeskills in most MMOs.

Preparation is required. Ever since the days of Ultima Online, we’ve relied on “getting the right pieces” to provide the fun in crafting. So we’ve done well on the “preparation is required” aspect of things as far as crafting goes. BUT: Preparation in itself ideally follows all of these rules recursively (eg, we should regard the harvesting mechanic as needing to follow all of these rules in and of itself). By and large, we have not done that. We also have usually failed to take full advantage of the “preparation should be able to take multiple forms” part of this—we have by and large gone with static ingredients for static results.

A sense of place is required. This is highly underexploited in crafting systems today. Different locales providing different advantages and disadvantages to crafting was explored a bit in Star Wars Galaxies, but has not been addressed much by and large.

A solid core mechanic. By and large, we’ve relied on simple combination. That’s not an interesting ruleset in and of itself—it shifts all the burden of fun onto the preparation. We need a mechanic that “fights back” as AIs do in combat. This is the core of the issue with crafting. It is currently on the order of moving a single checker piece, as opposed to playing checkers.

A range of challenges. This is, simply put, the range of possible craftables. However, it’s worth noting that since the solid core mechanic is missing, the range of challenges is not generally significantly interesting. The different items (as “opponents”) do not have different abilities or skill to use against you except for perhaps a variable failure rate.

A range of abilities required to solve the encounter. This is usually true to a degree, but currently, most crafting systems do not require interdependence between players at the actual crafting step. Instead, they put all of that in the resource gathering step. The abilities needed are part of the preparatory step, since there’s no explicit use of ability during crafting itself. Requiring multiple individuals working together to create something has best been expressed by pizza-making in Sims Online, and has hardly been used anywhere else.

Skill in using the abilities is required. This is missing altogether in most cases. There’s a minor amount of gambling in SWG’s crafting system, but that’s about it. Lacking a core, there’s no way to use abilities. A good core mechanic is going to provide scope for use of abilities, and for skillful application of those abilities.

A variable feedback system should be in place. In most cases, we do not do this. Currently, success almost always gives you exactly what you want. This means that crafting an item is actually simpler than moving a checker piece, which has multiple possible outcomes.

The Mastery Problem must be dealt with. This problem crushes most online game crafting systems, as high level crafters completely block the market to lower levels players.

Failure has a cost. This, we usually do.

In the end…

A game diagram can be regarded as fractal. When you diagram your game, each possible skill choice will be an atom, and systems will be built out of linked and nested atoms. From far away, the whole game looks like one atom, one where the failure and success cases are both “game over.”

If you have an atom that has a skill choice within it, and there’s no atom nested within it, you’re not done designing. If you have an atom that doesn’t hit all nine elements, that atom probably won’t be a fun game system, and needs to be redesigned.

Is this an algorithm for fun? No, but it’s a useful tool for checking on the absence of fun, in that you can identify systems that fail to meet all the criteria. As such, it may prove useful in terms of game critique. Simply check each system against this list:

Do you have to prepare before taking on the challenge?

Does the preparatory step pass this list as well?

Can you prepare in different ways and still succeed?

Does the environment in which the challenge takes place affect the challenge?

Are there solid rules defined for the challenge you undertake?

Can the one ruleset support multiple types of challenges?

Can the player bring multiple abilities to bear on the challenge?

At high levels of difficulty, does the player have to bring multiple abilities to bear on the challenge?

Is there skill involved in using an ability? (If not, is this a fundamental “move” in the game?)

Are there multiple success states to overcoming the challenge? (In other words, success should not have a single guaranteed result).

Do advanced players not get a benefit from tackling easy challenges?

Does failing at the challenge at the very least make you have to try again?

If any of the above answers is “no,” then the game system is probably worth re-addressing. (Source: Raph Koster’s Website)