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Defining Rule Space

Page: DesignArticle.Article-DefiningRuleSpace - Last Modified : Sat, 04 May 13 - 2203 Visits

Author : Eric Pietrocupo

I came up with a new concept lately after experimenting with one of my game. I'll start with an example as an illustration.

I have heard that in a Magic the Gathering tournament, there was a card where the rule stated that it must be dropped on the table and all the card it touched were destroyed. The player decided to tear up his card in hundred of pieces and dropped all the pieces over the opponent's playing field which destroyed almost every card he had.

This is a problem related to bad rule space definition. The reason is because the card's rule refer to a dexterity element of the game, but in magic the gathering, there is no dexterity element, and there is no rule regarding the positioning of the cards because it's not an analog game like "disk war". So the card's rule above was actually outside it's rule space.

Why should I use rule space

A rule space is like a subset of the area of effect. The area of effect contains all the possible effects a card can have, while a rule space is a group of special effects that you restrict yourself to use. Now most of the time, there are reasons why you want to restrict yourself to a certain rule space, it's really specific to the game you are making.

For example, in my game Fallen Kingdoms, there are 2 sources of special abilities: the knowledge and the gods power. The knowledge appeared in the game first and they are mostly rule changer abilities. Now when I wanted to define gods powers, I wanted something different. First because it would be more elegant and creative, but there is also a practical reason for it.

When you play the game, since knowledge are rule changer, you need to look at all the knowledge cards in play to see if they actually change some rules. If the gods power also change some rules, then it increases the number of cards the players needs to verify to see if a rule has been changed.

So instead, I decided that gods power would be used at the beginning of the turn, which restrict much more the rule space. Since it's used, the status of the game must be changed immediately. So some components on the board must be moved, added or removed. This reduces dramatically the possible abilities that can be made in this rule space compared to rule changing abilities.

Here is a graphical representation of the game's rule space:

Now you mights be wondering why the circle are intersecting, it's because I remember that 1 knowledge that has an effect at the beginning of the turn which actually does not change the rules. "Currency" increase all track by 1 point and the god "freya" gives 2 points to each track. So they are both game state changer, so in the future, It could be interesting to correct this "bug" and change the effect of "currency" to have better defined rule space.

Vinci example

In my remake of vinci, most civilizations special power affected the player who owned the civilization. Which means that they were only active during the player's turn. But a few abilities (I think diplomacy) affected players in other peoples turn. Now that was annoying because you had to check every time other people's ability in case one of their ability applied to you. But this situation did not arrive very often making it easy to forget. So when I redesigned the abilities, I made sure that all abilities affected the active player.

Still I cheated a bit. There was an ability called "Fortification" that allows players to place fortification tokens. Even if this ability was applied in the opponent's turn, there was a token on the board to remind you that there is a fortification. I pushed the concept forward and allowed fortification tokens to be used for other things than fortification. For example, "Traps" was another effect that used the same token. So when a player would attack a player with a fortification token on the board, it would act as a reminder that they should check the special ability of their opponent.

So this way, there are still abilities applied in opponent's turn, but there is a token to remind you. In small world, they made unique tokens for each ability making it even easier to recognize a defending ability.

Rule Space Intrusion

Another situation that triggered the idea to write this article was in the design of my Rats Craft game. I decided to set aside the combat system which is very complex to focus on the rest of the game and get back to the combat system later. I needed a replacement mechanic to test the rest of the game without working on the combat system. I know the final combat system will use cards, but let say I use dice as a replacement.

Let say I use the current rules for the combat system: Roll 1 die per rat in the room, the highest total wins.

The current variables are:

  • Is there a battle or not
  • The number of rats in the room

So if I design my game, the possible special abilities that will affect battle are rather limited. I could cancel a battle or make it happen when it should not. I can play with the number of rats by adding, moving or removing rats. But I cannot do much more. I cannot make the player re-roll or change the value of the roll, because the final mechanic will not use dice.

In this situation, I would say that the rule space cannot penetrate much the combat system which is pretty much isolated on it's own. That could be a design objective, but since I want more integration between both system to make sure the players does not feel like they are playing 2 separate games, I decided to proceed otherwise.

Since I knew I wanted to use cards, I decided to use the same components. So I borrowed the Rune Age combat system where every cards will simply have strength value. Players will play 1 card per rat and the highest total win. Again much more simple than what the real combat system will be, but this way my rule space has increased.

Because I can have many special abilities that will now affect the cost to buy the cards, the way the player draw and discards cards, etc. But most importantly, all those special abilities will be compatible with the final combat system. So no need to redesign anything without hindering the testability of the rest of the game.

Once the final combat system is finished, I could make some abilities affect the computation of the combat, but I think I prefer that they do not penetrate the combat system too much. Influencing the card flow seems more like an indirect interaction and I prefer it this way. Another indirect interaction I would use are bonus combat cards.

For example, I could have a building called "Anti-Air Turret" that would attack air units. Instead of saying that the turret destroy an air unit of strength X or less, I would say "add the anti-air turret card to your hand for the battle". The "Anti-Air Turrent" card can contain different values according to if I play with the temporary combat system or the final combat system. So when I will upgrade to the final combat system, I will not need to change the building's ability, but only the card's ability leaving the rest of the game intact.


So this is it, there is probably much more situation where rules space can be applied. Depending on the game you make, sometimes the area of effect is already small, so adding a rule space might make it too small. So it might be more suitable when the area of effect is too large. But you still have to set yourself minimum restriction to avoid the situation illustrated above in the Magic the Gathering tournament.

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