The Game Design Forum

Challenges, Cadences and Skill Themes

The purpose of a Reverse Design isn’t merely to accumulate data, especially since there is a ton of data on videogames these days. The greater purpose of a Reverse Design is to figure out what those data mean so that readers can learn from the masters. So the second step in the writing in the book was to look for patterns in the data. One of them is obvious: across the course of the game, the various jumps get harder. Donut Plains 3 and Chocolate Island 3 are almost the same level except that the later level has a larger average d-distance, significantly more enemies, and far fewer safe platforms.

This is something everyone knows: the game gets harder. One thing that surprised us, however, is that although some levels like the two above demonstrate clear numerical differences, most did not. There was no consistent measure that showed why later levels would be more difficult than earlier levels, so that hypothesis was falsified. Generally, the data suggest that every numerical factor in the game either peaks or plateaus not long after the player leaves Yoshi’s Island.

Interestingly, though, there is very consistent evidence that levels become more complex toward their respective ends, and so this is where most of the research was done. Much of the problem with measuring the whole game arises from the fact that it’s not entirely possible to compare early levels to late levels; the qualitative differences are often too great. Within levels, however, this is not so great a problem. In almost any level in the game, the relation between the end of the level and the beginning is fairly obvious.

For example, these are the first and last encounters possible with the Ball’n’Chain enemy in Vanilla Fortress. It’s pretty obvious that the second instance is a lot more difficult than the first, for both quantitative (amount of safe space, number of dangers) and qualitative (variety of dangers) reasons. This is true of almost every level in the game. Therefore, it stands to reason that the structure of levels might have something to tell us about how the game gets harder.


A challenge is the essential unit of content in a level: a cluster of actions that must be undertaken in one attempt, although that attempt can take a long time if the player chooses to stall, in many instances. Creating a universally applicable definition a challenge is impossible because although we strongly suspect that challenges exist in most modern games, their parameters differ greatly from game to game. They even differ from level to level. The most reliable indicator of the space between challenges is a safe platform. For example, the first and third shots here are the beginning and end of this challenge from Yoshi’s Island 3.

The challenge begins and ends in safety. (Incidentally, it’s also very safe in between because this is a perfect example of a training-wheels challenge.) Most challenges are like this; it seems that the design team wanted players to be able to plan ahead a little bit when going through any challenge. Sometimes this safety is broken up by a punctuating challenge, which is a kind of small mini-challenge that sometimes breaks up two challenges in a cadence. The definition of all of those things is below.


A cadence is the progression of challenges, explained by their relation to the standard challenge. Almost everything in a level relates back to the standard challenge clearly, although the punctuating challenge is often a minor exception to this. The only way to understand them is by seeing how they interact, so we’ll begin by defining that interaction.

Standard Challenge – The standard challenge is the first and most basic form of the challenges that get developed in the course of a level. The standard challenge is, in a sense, defined by its relation to later challenges. It’s not always the case that the first challenge in a level is the standard challenge. Sometimes the first challenge in a level doesn’t actually evolve, expand or mutate. Sometimes that first challenge is just there to accomplish something else, identifiable only on a case-by-case basis. Nevertheless, a standard challenge is usually simple, and no subsequent challenge in the cadence will be simpler qualitatively (excepting punctuating challenges, which are intentionally not developed), although some may be quantitatively easier to compensate for qualitative decay. My favorite level for illustrating cadences is Soda Lake. This is the standard challenge for Soda Lake:

The standard challenge contains a torpedo launcher with some accompanying Blurps. We’ll see how this grows in complexity as the level progresses.

Expansion Challenge – An expansion challenge is a standard challenge with one or more of the event variables increased numerically. An expansion challenge doesn’t change from the standard challenge qualitatively (or at least not by much), but it does change quantitatively. That is, the player is using the same skills in an expansion challenge as they would in a standard challenge, but the difficulty is greater because some aspect of the standard challenge has been increased. In Soda Lake, this is the first expansion:

The number of launchers and Blurps go up, but there’s still the same amount of swimming space and the terrain hasn’t increased in complexity. Although the position of the launchers has changed, it hasn’t evolved—it’s still on the edge of the screen rather than bisecting it or covering all of it in launchers.

There are many other ways to create an expansion challenge. These variables are common too:

D-Distance – The classic expansion in Mario is to simply increase the width of the pits he has to jump over. This makes jumping more difficult in a very obvious way. Most of the time, increases in d-distance will accompany other changes too. Delta Height – As we saw earlier, the bigger the difference in height, the harder it is to complete a jump—especially when jumping upwards. Often in an expansion challenge, an easy height will become a hard one as it expands, but everything else will remain the same.

Intercepts – The number of intercepts stationed around a challenge can go up, which makes the jump more difficult, up to a point. This is what’s happening in Soda Lake, since in water anything traveling at high speed is essentially an intercept. That’s not the only way that an intercept variable can be expanded, however. The intercepts can become faster and/or cover more ground than they did before. (A great example of this is Vanilla Secret 2, which we’ll see later.) Note that if the intercepts change in quality, i.e. a Koopa gets replaced by a Chuck, then it’s usually a mutation, not an expansion.

Penalty – Finally, the penalty of a challenge can be expanded. Often this means that the standard challenge has a penalty of one or zero (that is, failure to execute the challenge either hurts Mario, causing him to lose his powerup or does nothing to him) and the expansion raises the penalty to two—instant death. Most penalty expansions tend to take the penalty to two. The reason for this is that the game is using the expansion as a spot-check. A spot-check is a challenge that forces the player to demonstrate that they can execute a certain skill (or combination thereof) or else the player cannot progress any further. There’s usually no way to fumble through a spot-check. Sometimes Mario might take some damage, and then run through a challenge while he’s temporarily immune, but in a spot-check this is impossible. The good thing about expansion challenges is that even when they expand to spot-checks, the challenge is always something which the player has already done.

Evolution Challenge – In contrast to an expansion, an evolution is a qualitative change that uses all the same skills as the standard challenge but in a more qualitatively complex situation. In Soda Lake, the first evolution is this one.

Here, the two launchers from the previous expansion are split up to cover more of the screen. The quantitative elements are mostly the same: there are two launchers, and in fact there are fewer Blurps. (Technically, the amount of safe space has decreased, meaning this is both an evolution and an expansion.) The configuration of the launchers makes for an undeniably more complex challenge, however. Now rather than having one clear path to take, the player has to assess the two possible paths and choose the more likely. This is one form of the greater complexity that an evolution challenge accomplishes.

Note that evolutions and expansions don’t only evolve or expand from the standard challenge. The challenge above is actually an evolution upon the expansion, which in turn was an expansion upon the standard challenge. Or, to notate it:

  1. The Standard Challenge
  2. Then an expansion (X) upon the standard
  3. Then an evolution (V) upon that expansion

For a more in-depth look at notating the cadences of every level in Super Mario World and a statistical analysis on them, you can see the eBook version of this document, which contains lots of extra info about them including maps and charts.

Mutation - A mutation challenge is an iteration of any challenge that neither increases the complexity by evolution nor expands the quantitative aspects of the challenge that is being mutated. Rather, a mutation challenge simply reiterates a challenge in a slightly different way that is more or less equally challenging. To go back to Vanilla Fortress (because Soda Lake has no mutations) for a moment, these challenges are mutations of one another.

Although the second challenge has less theoretical space, it doesn’t have less functional space. That is to say, Mario doesn’t need a path both above and below the mace as it swings in loops: he can only take one path anyway, and so the path is effectively the same size in both. In the second case, he merely needs to swim up and shoot the gap with the slightest amount of forethought for timing. Essentially, the level is just giving the player a different look and asking him/her to fully explore the physics and pace of going up and down in the water. It’s not more complex, it’s just different.

Mutation challenges are important because not every single challenge can get more difficult or complex, or else many levels would become terribly tiresome. Part of establishing a good sense of pacing in level design lies in knowing when to give the player a break or an easy challenge to restore their morale and give their concentration a rest.

Training Wheels Challenge - A training-wheels challenge is designed to allow players to use new skills in a low-risk, easy-to-understand environment. Training-wheels challenges are especially prevalent in early levels, because they tend to occur in places where the player is using entirely new skills or new combinations of skills. In order to make acquisition of these skills easy and not frustrating, the designers do two things:

  1. Break what would be a standard challenge in any other level into its smallest component parts, teaching players how to execute each individual part of the challenge before putting them together (whereas an evolution would either throw them into a strange new element, added to the old, or combine two already-deadly challenges).
  2. Use one or more methods to reduce the penalty of the challenge down to 0.

You can see how this is a training-wheels challenge, because although the player can fail, the penalty portion of that failure is removed (as long as the player has activated the Yellow Switch Palace).

Plenty of challenges start off in simple forms and then assume more complex forms later in the level, but these are usually cases of evolution or expansion challenges, discussed above. A training-wheels challenge breaks everything down to its smallest parts, separating them down into single-element segments. Additionally, the penalty must come down. That is to say, if the standard challenge in the theoretical “normal” level features a bottomless pit, the training-wheels challenge either puts a floor over that pit (as in the example to come), or offers a damage floor or enemy-pit instead of an instant-death scenario, though it’s almost always a 0 penalty scenario. The point of the training-wheels challenge is to introduce the player to using new skills in the same harmless way training-wheels work on a bike.

Punctuating Challenge – The punctuating challenge is a kind of punctuation mark in the sentence of a cadence. It is sometimes used to cleanse the palate, so to speak. Rather than having the end of every challenge be a safe platform that starts the subsequent evolution, expansion or mutation, sometimes the designers will throw a simple punctuating challenge at the player to refresh and refocus him or her. Usually this means that there will be one or two stray enemies on a relatively large and otherwise safe platform. The key identifier of a punctuating challenge is that it is never developed. Although a punctuating challenge may be reiterated, it will never really evolve or expand, or else it would simply be a second standard challenge. Some levels have two standard challenges and juggle them both across a cadence, but most do not. We have largely omitted the mention of punctuating challenges, because although they have a place in the design of Super Mario World, almost everything that needs to be said about them has already been explained here. (There’s a little more said in the statistical analysis of cadences in the eBook.)

Crossover Challenge – A crossover challenge is a challenge that features a brief shift from one declension to another. They are generally brief, featuring five or fewer events, and rarely more than one or two sequential challenges. They are put in place to break the monotony of doing the same declension of challenge over and over (i.e. moving target jump after moving target jump). In Super Mario World, the crossover challenges are usually built out of the complement theme. That is, if the level is built around the preservation of momentum theme, the crossover challenge is built out of the enemy intercepts theme, and vice versa. Sometimes, especially later in the game, the crossover challenges are not made up of the complementary theme, but predominantly they are. Crossover challenges are important to a cadence because, since they arise out of the complement theme, they tend to work with the skills already in play in the cadence, rather than merely punctuating them.

Expansion by Contraction – This is just an expansion challenge that operates by narrowing the amount of safe space in a challenge. Like all oxymoronic terms, it exists because it describes a phenomenon more concisely than anything else would, while still being intelligible. Most expansions are literal expansions of some numerical element; in these cases, they’re just reductions in the size of safe space or beneficial features like platforms.

Reward by Fun – Occasionally, the designers will throw in a section in the game which is significantly easier than what surrounds it. The primary criterion for a reward by fun is the availability of non-death failure. Usually this means that Mario has to do something strange to get a reward. He can lose that reward, but it’s almost impossible for him to come to real harm—the only penalty is not succeeding. The Switch Palaces are good examples of this.

In each palace there is a challenge that the player can mess up, and therefore not gain all the potential rewards, but Mario’s death is pretty unlikely. This kind of challenge exists throughout the game, often as a kind of “comic relief” in the middle of otherwise difficult levels.


Just as jump events add up into challenges, challenges add up into skill themes. A skill theme is a series of levels which develop a consistent set of player skills through the use of fundamentally similar but ever-evolving challenges. While the entire game of Super Mario World gets harder, the exact methods are not necessarily quantifiable—or at least not consistently demonstrable as a quantitative increase. The qualitative evolution across the course of a game is very clear when looking at skill themes. By isolating levels that are “about” the same sorts of things, we can compare them apples-to-apples, as it were. But how do we identify which levels are in the same theme? This is where the knowledge of game design history becomes particularly important. Skill themes in a composite game are the material embodiment of composite design. A designer can take advantage of the various elements of the contributing composites to get specific effects in any given level. This is a little hard to understand out of context, but Super Mario World gives us many good examples. There are basically four skill themes in the game, and they lay out well on a matrix.

Naturally, two of the categories that are being crossed here are the two genres that Super Mario World combines, action and platforming. The other two categories are not historically derived, but are still plain to see in the game. “Speed” simply means that the level in question forces the player to steer Mario through challenges at a relatively high speed. Sometimes this is an obvious obstacle like a sinking platform that requires Mario’s speedy movement. Sometimes it’s an oncoming wave of enemies—that would be much harder to defeat than to avoid—that requires a quick reaction. In both cases, sustained speed and reflexes are more useful than slow, deliberate timing jumps.

On the other hand, there are many cases in which jumping headlong into a challenge at full momentum is either impossible or inadvisable. These are the timing situations pictured in the graphic. It might be possible for a skilled player to make the jump to the platform below (left) with full momentum. But it’s probably a lot easier to just wait a second or two for the platform to come back along its route. Similarly, a master level player might be able to react precisely enough to shoot tiny gaps in groups of periodic enemies, but it’s probably easier to wait for them to be in a better position. Recognizing these thematic cues in the environment is a key meta-skill that the player learns pretty quickly—mostly by dying! Just because the player recognizes that a section is action-oriented or momentum-oriented doesn’t mean that they’ve solved the section. A skill theme is, after all, made up of a variety of skills that the player has to master.

The definitions of everything written above are not meant to exist as concepts in isolation. The next section, which contains an analysis of every level in the game (except Bowser’s Castle) will illustrate all of these concepts copiously. Additionally, it should be noted here that not every level is in a skill theme. There are thirteen levels which are outside skill themes, although this doesn’t count two levels (Vanilla Secret 1, Gnarly) which occupy a mini-them of their own. That’s less than a quarter of all levels, however, and so the skill themes do account for most of the game’s organization.

Page 5: Skill Theme Intro/Moving Targets Theme Pt 1

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