Every day, I answer questions on my blog (called Blogatog; check it out if you've never seen it) about all sorts of Magic/game design–related things. On many days, one topic will grab people's attention and become the issue of the day. Today's article was inspired by one such "issue of the day." One involving this little guy:

This is Mowu. He's a good little dog. He's owned by (or maybe just friends with) a Planeswalker you all might know.

His name is Jiang Yanggu. He was one of two Planeswalkers we created for a Chinese introductory product. Most of the world first saw him in the Global Series before he showed up in War of the Spark. Note that Mowu has two forms, the smaller one seen in Yanggu's art and the bigger one seen in his own art.

Yanggu (the given name comes second in Chinese names) and Mowu inspired the Blogatog topic of the day because wherever Yanggu goes, Mowu follows. This might not seem like such a big deal, but, to some of my followers on my blog, it was. Why? Because Planeswalkers can't planeswalk with organic material. That's been a rule for all the Planeswalkers thus far. For example, Nicol Bolas had to go to great lengths to bring an army to Ravnica as part of his master plan in War of the Spark because of this restriction. How is it Yanggu can just disregard it?

I explained that the inability for Planeswalkers to carry organic material is a default rule, meaning that it's true for most Planeswalkers, but each Planeswalker can planeswalk a little differently. Some Planeswalkers can planeswalk with ease while others require great concentration. Some can planeswalk again quickly while others have to wait longer. The amount of inorganic material they can carry varies. And, some can carry organic material, but, so far, the few who can are very limited in what they can bring. (For example, Yanggu can only bring Mowu and Wrenn can only bring her bonded treefolk, currently Six.)

The response to that was why could we break that rule while I was holding so firm to red being unable to destroy enchantments, something mono-red players have been asking for forever. Why was it okay for Planeswalkers to break their rules but for colors not to break theirs? That was a great question, but one complicated enough that I realized I needed a whole column to do it justice. This is that column. So, buckle in, it's time to start talking about rules.

Ground Rules

Back in 2011, I wrote an article called "Ten Things Every Game Needs." One of the ten items was rules. Let's start by talking about why games have rules in the first place. What's the purpose of having rules?

#1 – Create Obstacles

A game is essentially a goal with obstacles in the way preventing you from easily reaching the goal. The joy of playing a game is figuring out how to navigate the obstacles to achieve the goal. The obstacles are key because it's the overcoming of them that provides the thrill. If the game was Ring the Bell and there was just a bell sitting there that you could pick up and ring, it wouldn't be all that compelling. Rules are what create obstacles. They define what you, as a player, are and aren't allowed to do.

#2 – Establish Structure

Rules are the backbone that a game is built around. There's a reason that every game begins with learning the rules. They explain to the players what to expect and what is possible. Some games provide all the rules up front, while others dole out the rules as the game progresses, usually through game pieces, allowing players to uncover new rules as they play the game. (Magic, obviously, falls in the latter camp.)

#3 - Provide Clarity

The world is filled with ambiguity. It's the job of the rules to eliminate ambiguity within the context of the game. The players have to understand what they can and can't do, otherwise the game falls apart as the focus shifts to how the game works rather than what the players are trying to do within the game. Some games, like Magic, have a very complicated set of rules due to the complexity of the game.

#4 – Ease Decision Making

The human brain has a problem with having too many options. For example, "What do you want to eat for dinner?" is a harder question than "Would you prefer Italian or Mexican for dinner?" If your game always allowed infinite choices, most players would freeze up. Rules do a good job of limiting options, making it easier for players to reach decisions. In Magic, for instance, the mana system limits what cards can be played on any one turn, reducing your choices and making it easier to figure out what to cast next.

#5 - Set Expectations

The unknown is scary, so people like having some ability to predict what's coming next. The rules do a good job of limiting future possibilities, allowing players to think ahead and make reasonable assumptions of what they can expect.

#6 – Allow Comfort

Back in 2013, I wrote an article talking about how you could apply the rules of communication theory (in college, I attended a communications school) to game design. One of the key elements of communication is understanding the human need for comfort. People are just happier if they're familiar with the thing they're interacting with. In communication, this is done through repetition. A magazine, for example, will almost always have the same sections with the same format in the same order. Rules do a similar thing for games where they create a known structure that allows players to gain a sense of familiarity. It brings a sense of comfort, which puts them at ease.

#7 – Enable Surprise

Another part of communication theory is that humans like surprise, but only when in a place of comfort. The rules not only provide the comfort, but they also set up the game designer to create surprises. The creation of rules allows for the breaking of rules, aka having the game take a turn the audience can't anticipate because it specifically works against expectation. If anything was possible, it would be much harder to surprise the players.

As you can see, rules do a lot; they carry a lot of weight in making the game playable and fun. But all rules are not created equal, which gets us to the crux of today's column, the two different type of rules—what I'm going to call constraints and defaults.


A constraint is a rule or set of rules that is designed to be absolute. That is, they are rules that are created specifically never to be broken. They exist because they serve an important function in making the game work. To use a favorite metaphor, constraints are like load-bearing walls in a house. They have to exist because they are literally holding the house up. You might want to knock one down to make a room bigger, but you can't because it serves a larger purpose. This is essentially how constraints work. On the surface, they might seem like just any other rule, but behind the scenes, they serve a larger purpose.

Let's take the color pie as an example. Trading card games allow players to choose among all the cards (or a subset of cards if the format doesn't use all the cards) to build their deck. If there weren't any constraints built into the game, there would be one optimal deck using all the best cards available. This is what Richard Garfield called the Queen Problem. If you could choose what chess pieces you played with, why wouldn't everyone just bring fifteen queens and a king (with the assumption that each player has to have a king, as it provides the win condition).

The mana system and the color pie were created as means to solve this problem. The mana system forces players to play a range of costs because their value changes as the game progresses. The mana system and the color pie force players to pick a color or colors to ensure that they're able to cast their spells. The color pie has strengths and weaknesses for each color, to create more variety and allow for counter-strategies. The rules about what colors can and can't do need some constraints to ensure that over time they don't just all morph into feeling the same. If that happened, the available space for card design would collapse and the game would lose much of its flavor and variety.

In order for a color to not be able to do something, we have to be vigilant about not doing it. Even doing it once changes expectations about how the color functions. The pain Planar Chaos has brought me has become a running joke on my blog because it's the set where we were experimenting with the color pie. Now often when I say we don't do something in a color, one of my followers posts, "But what about this card from Planar Chaos?" Magic is a game where cards exist forever once they're printed (especially in formats like Commander that have access to most of the cards), so we have to be extra careful about holding firm to our constraints.


A default is a rule or set of rules that are designed to function the majority of the time. If no outside force is impacting the game, these rules should stand. They are the way the game is supposed to function as a default. Using my wall metaphor, defaults are decorative walls. These are walls that are intended in the blueprints to be in a certain place, but if a specific house has need to shift or remove them, that can be done without causing any building-integrity issues. The architect has reasons why they want the decorative walls there, so if there's not some larger issue, they should stay that way—but that's not an absolute.

For this example, let's take the planeswalking rules. Planeswalkers are the key signifier of Magic. That is, they are the thing most unique to the game, something that sets Magic apart from other games and intellectual properties. The players take on the role of Planeswalker, so it's pretty integral to both the game and the larger story. Because Planeswalkers are so important, we want to make sure we design planeswalking in a manner that allows us to make our Planeswalkers as interesting and compelling as possible.

To do this, we made the conscious choice to have each Planeswalker planeswalk differently. Rather than have each Planeswalker follow the exact same rules, we created a default of how average planeswalking works, but we allowed ourselves the freedom to have variance between Planeswalkers. Why? Because it's more compelling if we have the freedom to make characters a bit different from one another. If most Planeswalkers can't do something, but then a Planeswalker shows up who can do that thing, it's exciting. It makes for good storytelling and dynamic character building.

Rules of the Game

With those two terms defined, let's look into a few things about how they function.

You Don't Want Your Audience to Know the Difference

While you, the creator of the game and the rules, need to understand exactly what is a constraint and what's a default, you're actually disincentivized from being very vocal about it. Why? Because you want the ability to surprise your audience. If the audience is aware what rules can and can't be broken, it lessens your ability to surprise them when you break one. I will admit that Magic is in a different spot in this area than most games for two reasons. One, we are very transparent about how we make our game and I, in particular, spend a lot of time showing you all behind the curtain. Two, Magic is a very complex game, so it has a lot more rules than the average game, making it easier for us to break rules where you might not expect.

Players Assume Every Rule Is a Constraint

I explained above the numerous reasons why rules are comforting to your players. In addition, humans love structure, so rules are easy to latch onto. What this means is once players get used to a rule, they tend to expect it to continue, and the longer it exists, the stronger they anticipate it never being broken. That's why introducing a new keyword doesn't tend to throw players as Magic is constantly doing that, but printing double-faced cards for the first time created an uproar because "Magic cards don't do that."

Once a Rule Is Broken, Players Assume It's a Default

But, once you break a rule, players (after they get used to the change) now feel the rule is fair game. For instance, this whole article was about all the email I got about Yanggu and Mowu, yet I've received almost nothing about Wrenn and Six. This is another reason breaking a constraint is so bad, because it leads to the expectation that more breaks are to come. (Again, curse you Planar Chaos!)

Dog Days

With all this context, let's dig into the Yanggu/Mowu issue. To do that, I want to examine the creation of the "can't planeswalk with organic material" rule. To do that, we have to back up a bit and examine what defines a Planeswalker. As I said above, they are core and integral to Magic, so we need to understand why. I think the answer to their definition is in the name—Planeswalkers walk between Planes. Magic is a Multiverse filled with a myriad of different worlds, and only the Planeswalkers have access to them. Except, in early Magic, that wasn't true. There were portals and vehicles and various things that allowed non-Planeswalkers to move between the Planes. That made Planeswalkers a lot less special. To fix this, we created the Mending, the story during Time Spiral block, that rewrote the rules for planeswalking. One of the biggest changes was eliminating all the other ways to travel between Planes. If you want to move between worlds, you have to be a Planeswalker.

The point of this rule was to make Planeswalkers special. The reason Planeswalkers don't planeswalk with organic material is so we don't undermine the uniqueness of Planeswalkers. A Planeswalker can't simply transport a non-planeswalking character to another world. Does a boy planeswalking specifically with his dog or a dryad planeswalking specifically with her bonded treefolk undermine that uniqueness? No. In fact, I think having the occasional allowance, when kept very specific, is a boon to the game, not a drawback. The majority response to Yanggu was not "How can he do that?" but "Ooh, a doggie." The players enjoyed the specialness of Yanggu. And that's the goal of Planeswalker creation—making Planeswalker characters players can bond with. Note that the larger rule of not undermining planeswalking is still in effect. I don't think we'd make a Planeswalker that can just bring any number of passengers along. Both Yanggu and Wrenn purposely come with very stringent restrictions.

Remember, the purpose of your rules is to be tools enabling you, the game designer, to make the most compelling game possible. It's not to make unnecessary restrictions for the sake of restrictions. Yes, I do believe restrictions breed creativity, but you want your restrictions to come organically from what you're doing. Saying you can never move a decorative wall just because you said you can never move it doesn't lead to building the best house. Your restrictions should be your constraints, not your defaults.

The reason I've spent an entire article on this topic is because I think it's important for game designers to understand when and how you break your rules. Never breaking them can lead to a staid game with no surprises, while breaking rules just to break them can cause long-term harm to your game. The key to knowing when and how to break them starts with understanding what each rule is doing for your game.

So how do you know which is which? The answer is you experiment with removing a rule and see what happens.

In Innistrad design, we were trying to figure out how to design Werewolves. Borrowing a page from Duel Masters (another trading card game we make), we tried double-faced cards. I got a lot of resistance because "Magic cards have a back," but the more we played with it, the more we realized it was compelling content that was worthy of releasing. Magic cards having a back wasn't the constraint I thought it was.

In Tempest design, I designed a mechanic where you could choose to start with a card that had the mechanic in your opening hand, but you drew one less card. All the cards with the mechanic were costed to be a bit below the normal power level of a similar card. It only took one playtest to see the problem. Even at a lower power level, you often wanted the guarantee of getting a certain kind of card. Having it always be in your opening hand just made the gameplay the same every time. Without realizing it, I had broken a constraint—that the card draw needed to be random—and it was obvious right away I was breaking a rule that shouldn't be broken.

The key is recognizing what the rule adds to the game and what happens when it gets broken. Red having enchantment removal would fundamentally change how the color pie works. Yanggu bringing Mowu along makes a compelling new character. Those two things are very different rules and need to be treated accordingly.

Rule Out

And that brings us to the end of today's column. I've been doing a bunch of podcasts using my blog as fodder for topics. I'm curious what you all think of me doing it more for my column. As always, you can contact me through my email or any of my social media accounts (Tumblr, Twitter, and Instagram). Please let me know your thoughts on today's column and any points I made in it. As always, I appreciate your feedback.

Join me next week (in the evening on Saturday, July 20, after our San Diego Comic-Con panel) for one of those articles I do that gets everyone talking.

Until then, may you find someone as faithful as Mowu.

#653: Other Lessons – Ideas & Execution
#653: Other Lessons – Ideas & Execution


As a new series following up my "20 Lessons, 20 Podcasts" series, I'm starting "Other Lessons" to talk about other things I've learned during my time at Wizards. This podcast's lesson is "People overrate ideas and underrate execution."

#654: War of the Spark Cards, Part 4
#654: War of the Spark Cards, Part 4


This is part four of a five-part series on card-by-card design stories from War of the Spark.