Good and Great Possibility Space

Hello, today I want to share my opinion about great possibility space.

First I’d like to explain what I mean when I talk about possibility space.

The possibility space is the amount of choices and the different results of these choices a player can experience when playing your game. These number of different outcomes can be high, which leads to a big possibility space or it can be low, which leads to the opposite.

I like games with a high possibility space. For me, making decisions is the unique attribute that differentiates games from other entertainment media. That's why I think that good games embrace player choices and aspire a big and great possibility space that keeps players engaged for a long time.

Causes that create a great possibility space

Number of choices

You’re may be able to increase the possibility space of your game by increasing the number of choices your players can make. Unfortunately it’s not that simple. Increasing the choices doesn’t have to create a bigger possibility space. The number different outcomes is what defines the possibility space. If nine out of ten decisions always lead to the same outcome your game effectively provides only two decisions and has a much smaller possibility space than you might think. But having choices that lead to different outcomes do indeed increase your games possibility space, which makes this tool a valuable asset.

Dependencies between mechanics

Players can interact with certain game mechanics to influence the game state which may lead to different outcomes. Good mechanics that have a certain depth should be able to influence your system in more than only one meaningful way due to their relationships to other mechanics in your game. This way your player can make decisions that can lead to a wide number of new outcomes due to the complexity of your system. Players can use different mechanics in different ways which lead to even more different outcomes and by this to a much greater possibility space.

In theory this is a very strong tool to increase your games possibility space but some games push this emergence of possibility space a little too far. Often game systems can become so complex that even the designers do not know all the different outcomes can be created with the provided systems. This may lead to an emergence of possibility space that you want to avoid. I try to give an explanation where a mechanic is used in a great way and in a less good way when creating possibility space with an example from a game I really like a lot: Heroes of the Storm.

Most of the time you can see where Blizzard wants to give their players choices that lead to a great possibility space. These choices are very obvious and it’s clear to see where players should make these choices. For example the talent system in Heroes of the Storm that affects the skills and attributes of the heroes. The different combinations in relationship to the different use cases on the different maps, combined with 4 other heroes already lead to an almost immeasurable possibility space. It is easy to grasp and players can think about the different possibilities as soon as they start to play the game.

But there are also mechanics that lead to a not so obvious possibility space but were definitely intended by Blizzard. In Heroes of the Storm heroes can block other heroes movement. The path finding algorithm tries to find a way around the other heroes but it seems that Blizzard tuned this algorithm in a way that makes blocking other heroes possible as they tend to change their direction a lot of times when trying to pass another hero.

I really like this mechanic as it provides gameplay to a mechanic that is easy to grasp and very essential to the game: Moving your hero. On the other side, this mechanic is very natural as you can see this kind of behavior in other games like football and soccer.

But the same mechanic is used by professional teams in a not so obvious way as it also can be used to block your own minions (units controlled by the AI). Most of the time it is useless to do that because minions have a much smaller hitbox than heroes and it is very very hard to block their movement in a meaningful way. Nonetheless in professional games the teams tend to block the first minion wave with all their five heroes so the first combat emerges closer to their defending towers which is an advantage.

This emergence of a strategy may seem to be something good but in my opinion it is not due to three reasons:

1. Both teams will make use of this mechanic and can’t influence the other team while doing the same. This leads to the situation that it doesn’t matter that both teams know about this “strategy” as it’s a dominating strategy that has no counterplay. It doesn’t offer a choice it only offers a dull task.
   
2. The blocking of such a small hitbox feels pretty random. It looks arbitrary how the heroes try to block the minions and how the minions react to the movement of the heroes. That way both teams will achieve almost the same results and if they don't, the outcome seems to be pretty random. The cause and effect between the movement of the heroes and the movement of the minions is too loose to provide valuable feedback to the player.
   
3. Blocking heroes so they have a harder time to escape from or chase other heroes feels natural and has clear parallels to other games (e.g. Football). Blocking your own group of minions so they are slower and arrive later on the battlefield is a much less natural and a very counter intuitive strategy and doesn't serve the fantasy of the game.

I think as a Game Designer you should really know where you want to create the possibility space in your game with the different mechanics that your game provides. Players should be able to guess where they can explore the different strategies and outcomes of your games possibility space without being completely surprised by artificial and absolutely non obvious and counter intuitive usage of mechanics.

Sometimes the reason for emerging strategies is even out of the designers control (e.g. technical).

World of Warcraft has an Arena Mode where players can fight against each other in small teams. A lot of characters need mana to use certain skills. Mana can be regained by drinking but drinking can only be done when players are out of combat, which means that they didn’t participate in any combat action for about 8 seconds. There was a time when players (especially players that played a healing class) were able to abuse the out of combat / drinking mechanic in the arena to regenerate their mana even if they were in combat. The only thing they had to do was to wait until their character was out of combat and then started to  cast their biggest and strongest heal spell of their character with the longest casting time. Channeling the spell didn't count as a combat activity, only as soon as their target which was in combat gained the healing of the spell they were flagged as “in combat”. By spamming the drinking button while casting the spell they were able to drink after they have healed their partner because the server recognized too late that their character participated in a combat activity by a few milliseconds. They started drinking after the spell and as were flagged a short time after they have started to drink which didn’t interrupt the drinking. This behaviour led to combats where people that waited until they were out of combat, used a spell, spammed the drinking button and then started drinking even if they were in combat had an advantage because they could regain mana without renouncing to heal their partner. It was a strong strategy and every top team had to make use of this mechanic to be able to keep up with the other teams.

I hope this article helped you to get a better feeling of possibility space in games and the problems that you may face when designing your game.