作者：Mark Venturelli

我将在本文讨论有关明智使用玩家选择限制的话题，其中包括可能性空间，涉及挑战，以及来自其他游戏的一些正反面案例。

约束对你有好处

游戏设计主要是选择的设计。我们作为设计师有相当一部分工作是为玩家创造体验，为之提供一系列有趣的选择——这在象棋或《万智牌》等回合制游戏中是个更容易理解的概念，但它也适用于即时游戏。在玩《Dungeonland》的时候，我是否会停止攻击去解救附近的一个同盟？我是否现在就使用自己的特殊药剂，还是留着之后备用？我是否要先躲避一下还是继续攻击那个敌人？

设计的基本要素之一就是“可能性空间”。我已经在数年前写过关于这个话题的一篇文章，所以不打算在此赘述，但通常情况下它代表玩家在特定时间点所拥有的选择。更少选择，意味着更小的可能性空间，更多选择就是更大的可能性空间。

我们很容易认为“越多越好”，但事实并非如此，正如《文明IV》设计师Soren Johnson去年所写的文章曾指出，如果你给予玩家过多选择，他们可能就只会随便挑选，或者坚持自己原来试过的方法。这两种情况都不能算是很有趣的玩法。

我一直在捍卫“高度集中”式，只保留绝对必要，删除任何“不必要”环节的游戏设计理念——《Dungeonland》几乎就是围绕这一理念而设计。我仍然认为这种极具约束性的方法是设计游戏的可行之道，但我还发现了一种更为平衡的方法。

约束并不适合你

那么当你限制可能性空间，只保留最重要的决策，并删减其他内容时，你的系统会发生什么情况？

简单性/复杂性与浅显/深度之间总处于一种恒定的紧张状态。当世界充满大量极富深度的简单游戏，以及极为肤浅的复杂游戏时，制作简单但富有深度的游戏就是一项罕见的成就。这一切都要取决于你的机制如何整合在一起：紧凑的游戏每次玩起来的感觉都极为不同，它们的配置只要有极小的变化就可以创造新的情境。所以，当我设计一款游戏时，我面临的个人挑战就是“我想用最简单可行的系统设计自己所能达到的最有深度的游戏”。

这非常困难，真的很难。虽然我很为自己在《Dungeonland》的战斗系统中所获得的成就而自豪，但它还是不够有深度。这就是问题所在：你得从极为简单的机制中提取良好的深度，但你的游戏深度够吗？《Dungeonland》当然还使用了一些额外的深度，我从那种体验中得到了许多收获。

我们最终想要的就是大量的即兴潜力。我们想让自己的系统发挥超出预期的表现，让我们感到惊喜，在每次我们每次接触时都会产生新玩法故事。有时候你可能会看似不经意地将自己的设计限制于一个单一的工具中。

创造更多优美的约束条件

我现在设计的是《Chroma Squad》这种战术性回合制战斗游戏。这个游戏题材拥有大量单位，每个单位都有不同的能力和属性，不同的地形/障碍和不可名状的东西，尤其是可从约束可能性空间得到的好处。我们将察看这个题材中关于单位移动和定位的两个采用了普遍约束方法的好例子，它们分别是《幽浮：未知敌人》和《韦诺之战》。

battle-for-wesnoth(from gamasutra)

这两款游戏的设计师似乎都意识到了同样的情况：你可以使用“软”方法来限制玩家的选择，而不是完全限制选项。每个单位都可以向玩家所想要的方向移动，但这并非玩家“解读”每个回合的方式。

在《幽浮：未知敌人》中，每个地点都有一个“困难”属性，或者是无掩护，半掩护或是全掩护。让你的军队处于毫无掩护的状态无疑是个糟糕的主意，所以玩家几乎都会让自己的军队向全掩护方向移动（至少也要半掩护）。在执行良好的关卡设计中，这种做法创造的是移动单位时合理约束玩家可能性空间的结果：你总是有一大把“真正的”选择，即便你在必要的时候可以自由地离开安全路径。尽管在移动过程中还需要考虑其他许多因素，例如翼侧包围，视线和射程等，最终你要先通过掩护地点“筛除”这些选项。

在《韦诺之战》中，开发者采用了一种与《Fire Emblem》游戏所不同的地形系统——不同的地形拥有一个“防御”比例值，可以增加敌人攻击失误的概率。不同军队也可以用不同方法利用地形优势——Elven军队可以从森林中获得额外加成，而Dwarves在山上更易于防守。它创造了一种类似于《幽浮》系统的效果——即便你可以向任意方向移动军队，你可以首先通过最佳地理位置来筛选合理的行动。

移除约束条件

所以想象一下，如果新的《幽浮》并没有掩护规则，或者它们并不像当前设计一样看重保证玩家军队存活率，情况又会如何呢？玩家可能就得考虑关于射程、视线和翼侧包围等因素的更多选项，而突然提前想到两三个回合则是一个极为困难的任务。这样的游戏可能会令人感觉较不“紧凑”，其中的回合持续时间更长。

此外，如果《韦诺之战》中所有的地形都是平的，那就会出现相似的效果：敌人的行动会突然变得几乎不可预测，要想有效移动每个单位就需要玩家额外多花点时间分析可能出现的结果——换句话说，你可能会无所谓向任何方向移动，只能寄希望于出现最好的结果。由于游戏未来状态变得更加难以预测，玩家身上可能就会出现大家所不希望看到的分析麻痹症——游戏永远没有真正的选择，玩家就只能随机选择。

强化约束条件

现在从一个不同的角度来考虑：如果在《幽浮》中你只能向掩护地点移动单队呢？就好像在5th Cell的射击游戏《Hybrid》中一样，所有向非掩护地点移动的行为都会被禁止。在某些情况下，玩《幽浮》的体验会令人意外的完整，但你可能会失去大量即兴玩法。我记得有几次我的士兵疾跑到空旷地反败为胜，但如果Firaxis选择运用这种约束条件，游戏就不可能出现这种情况了。

这种做法值得一试吗？在我看来，答案是否定的。从许多方面来看，这正是他们的战略层次：仅浓缩最为基本的选择，结果就无甚新意了。你可能没听说过《幽浮》在战略层次方面的一种情况——有趣的事情只会发生在地面，这真是一个遗憾，要知道它继承了原版游戏丰富的即兴玩法。我在《Dungeonland》中多方面运用了这种“过于约束”的方法，事后看来我发现自己让玩家错过了一些冒险一搏的机会。（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）

Constraining The Space of Possibility

by Mark Venturelli

In this week’s article I’m going to talk about the smart use of constraints for player choice. I’ll provide you with a quick view on space of possibility, the challenges involved, and some good and bad examples from other games.

Constraints Are Good For You

Game design is primarily choice design. The bulk of what we do as designers is to create an experience for the player that arises from providing them with a series of interesting choices – this is an easier concept to grasp in turn-based games such as Chess or Magic: The Gathering, where these moments of decision are discrete, but it also applies to real-time games. While playing Dungeonland, do I stop attacking to try and revive a nearby ally? Do I use my special Potion right now, or do I save it for later? Do I dodge roll to the right or do I keep attacking that enemy?

One of the fundamental things about design, then, is the “space of possibility”. I’ve wrote an article about that a few years ago so I won’t be going in-depth here, but generally it represents all the choices a player has at his disposal at a certain point in time. Fewer options, smaller space of possibility; lots of options, bigger space of possibility.

It’s easy to think that “the more, the merrier”, but this is hardly the case, as Civ IV designer Soren Johnson wrote about last year. If you swarm a player with too many choices, they will either pick randomly, or stick with what they have tried before. Both cases are usually not considered very interesting play.

I have always defended “laser-focused” game design that keeps only what is absolutely needed and cuts off any “unnecessary” parts – Dungeonland was mostly designed with this mentality. I still think this constraint-heavy approach is a valid way of designing games, but I’ve been exploring a more balanced approach.

Constraints Are Not Good For You

So what happens to your system when you constrain the space of possibility to the most important decisions and leave the rest in the cutting room floor?

There is constant tension between simplicity/complexity and shallowness/depth. While the world is filled with examples of simple games that are extremely deep and complex games that are extremely shallow, making a simple-but-deep game is a rare achievement. Everything comes down to how integrated your mechanics are: tightly-woven games will play very differently every time and make new situations emerge with very small changes in their configurations. So when I design a game my personal challenge always is “I want to design the deepest game that I can with the simplest possible system”.

This is very hard. Really hard. While I’m ultimately proud of what I achieved with Dungeonland’s combat, ultimately it wasn’t as deep as it should be. And that’s the question: you have extracted good depth from your very simple mechanics, but is your game deep enough? Dungeonland sure could have used a few extra feet of depth in there, and I have learned a lot from that experience.

Ultimately what we want is to have a lot of potential for emergence. We want our system to behave in unexpected ways, to surprise us, to be a generator of new gameplay stories every time we play. Sometimes you can inadvertently constrain your design into a single-note instrument.

Creating More Elegant Constraints

So I’m currently designing Chroma Squad, which features tactical turn-based combat. This a genre that, with multiple units, each usually with different abilities and attributes, different terrain types/obstacles and whatnot, especially benefits from a smart approach of constraining the space of possibility. We will look at two good examples of unit movement and positioning in this genre that share a common approach of constraining: XCOM: Enemy Unknown and Battle for Wesnoth.

Both games’ designers seem to have realised the same thing: you can use “soft” limits on player choice instead of limiting options altogether. Each unit is allowed to move pretty much anywhere the player wants, but that’s not how players “read” each turn.

In XCOM: Enemy Unknown, each location has one of 3 “hard” attributes: No Cover, Half Cover or Full Cover. Leaving your units out in the open is usually a terrible idea, so players will almost always move their units towards Full Cover (or at the very least Half Cover) locations. With well-executed level design, what this creates is an elegant constraining of players’ space of possibility when moving units: you always have just a handful of “real” choices to make, even though you are free to stray off the safe path every once in a while if the situation calls for it. While there are many other considerations to make when moving, such as flanking, line of sight and range, ultimately you are first “filtering” these options through the Cover spots first.

In Battle for Wesnoth (a brilliant open-source tactical game which you should absolutely play if you haven’t already), they adopt a terrain system not unlike the one found in the Fire Emblem games – different terrain types have a “defense” percentage value that increases the chance for enemy attacks to miss. Different units also take advantage of terrains differently – Elven units gain extra bonuses from forests, while Dwarves are more protected at hills. It creates a similar effect to XCOM’s system – even though you can move units anywhere, you are usually filtering the possible moves through the best terrain positions first.

Removing the Constraints

So imagine if the new XCOM did not have these cover rules, or if they were not as important to keep your units alive as they are in the current design. Players would have to consider a LOT more options for range, line-of-sight and flanking, and suddenly looking two or three turns ahead would be an herculean task. The game would feel less “tight”, if I may use a looser term, with turns lasting longer.

Also, if all terrains in Battle for Wesnoth were flat, there would be a similar effect: enemy movement is suddenly near-unpredictable, and moving each unit effectively would require several minutes of analyzing the possible consequences – in other words, you would just not care and would move anywhere, hoping for the best. As predicting future states of the game becomes harder, the generally unwanted effect of analysis paralysis occurs – a real choice never occurs, and the player ends up choosing randomly.

Reinforcing the Constraints

But now picture it from a different angle: what if in XCOM you could ONLY move your units to cover spots? Much like in 5th Cell’s shooter Hybrid, all movement to points that are not in cover would not be permitted. In several cases, the experience of playing XCOM would be surprisingly intact, but you would lose a lot of emergent potential. I can remember several occasions when I had soldiers sprint out in the open and save the day, and these stories would not be possible if Firaxis had chosen to apply this constraint.

Would it be worth it? In my humble opinion, absolutely not. In many ways, this is what happened to their strategy layer: boiled down to only the most fundamental choices, the end result is stale. You hardly hear a story about XCOM in the strategy layer – the cool stuff only happens on the ground, which is a shame considering the rich heritage of emergence from the original game.

In many ways, this “too-constrained” approach was the one I used in Dungeonland, and in hindsight I can see several missed opportunities for letting players venture off the beaten path.（source：gamasutra）