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# Game Mechanics: How to Design an Internal Economy for Your Game

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## Uses for Internal Economies in Games

In the previous sections, we discussed the elements and common structures of internal game economies. In this section, we will discuss how game economies are typically used in games of different genres. Table 1.1 provided a quick overview of some mechanics that are typically part of that economy. Now, we will discuss the typical economic structures found across game genres in more detail.

### Use an Internal Economy to Complement Physics

Obviously, physics make up the largest part of action games’ core mechanics. Physics are used to test the player’s dexterity, timing, and accuracy. Still, most action games add an internal economy to create an integral reward system or to establish a system of power-ups that requires resources. In a way, the simple use of a scoring system adds economic mechanics to many action games. If you collect points for taking out enemies, players will have to consider how much they will invest to take out that enemy. Will they put their avatars at risk, or will they waste ammunition or some sort of energy that cannot easily be regained?

Super Mario Brothers and many other similar platform games use a simple economy to create a reward system. In Super Mario Brothers, you can collect coins to gain extra lives. Because you need to collect quite a few coins, the designer can place them liberally throughout a level and add or remove them during play-testing without affecting the economy significantly. In this way, coins can be used to guide a player through a level. (Collectible objects that are used to guide players are often called breadcrumbs.) It is safe to assume that you are able to reach all coins, so if you spot a coin, there must be a way to reach it. This creates the opportunity to reward skillful players for reaching difficult places in the game. Used in this way, the internal economy of the game can be very simple. However, even a simple economy like this already involves a feedback loop. If players go out of their way to collect many coins, they will gain more lives, thus allowing them to take more risks to collect more coins.

When setting up a system like this, you must be careful to balance the risks and rewards. If you lure players into deadly traps with just a single coin, you are inviting them to risk a life to gain a single coin. That simply isn’t fair, and the player will probably feel cheated. As a designer, you have a responsibility to match the risks and rewards, especially when they are placed close to the path novice players will take. (Creating a reward that the player can see but never reach is even worse—it causes players to take risks for rewards they can never obtain.)

Power-ups, including weapons and ammunition in first-person shooters, create a similar economy. Power-ups and ammo can be rewards in themselves, challenging the player to try to eliminate all enemies in a level. As a game designer, you have to make sure that the balance is right. In some games, it is perfectly all right if killing enemies will, on average, cost more bullets than the players can loot from their remains. However, if this leads to a situation in which the player is eventually short on the proper ammo for the big confrontation with a boss character, you risk penalizing players for making an effort in the game. In survival-oriented first-person shooters, creating a scarce economy of weapons and ammo is generally a good thing because it adds to the tension and the drama, but it is a difficult balance to create. If your shooter is more action-oriented, then it is probably best to make sure there is plenty of ammo for the player, and you should make sure that taking out extra enemies is properly rewarded.

### Use an Internal Economy to Influence Progression

The internal economy of a game can also be used to influence progression through a game that involves movement. For example, power-ups and unique weapons can play a special role in an action game’s economy. They can be used to gain access to new locations. A double-jump ability in a platform game will allow the player to reach higher platforms that were initially unreachable. In economic terms, you can think of these abilities as new resources to produce the abstract resource access. Access can be used to gain more rewards or can be required to progress through the game.

In both cases, as a designer, you should be wary of a deadlock situation. For example, you might have a special enemy guard the exit of a level. Somewhere in the same level there is a unique weapon that is required to kill that enemy with a single shot. The weapon is usable throughout the level. When the player finds the weapon, it is loaded with ten bullets, and there are no more until the next level—but the player doesn’t know this the first time playing. Now, a first-time player finds the weapon, fires a couple of shots to experiment with it, uses it on a couple of other enemies, and finds himself at the exit with one bullet left. The player fires and misses. You have just created a deadlock situation. The player needs access to the next level to gain bullets but needs bullets to gain access.

### Use an Internal Economy to Add Strategic Gameplay

It is surprising how many of the strategic challenges in real-time strategy games are economic in nature. In a typical game of StarCraft, you probably spend more time managing the economy than fighting the battle. Including an internal economy is a good way to introduce a strategic dimension to a game that operates on a larger time span than most physical and/or tactical action.

One of the reasons that most real-time strategy games have elaborate internal economies is that these economies allow the games to reward planning and long-term investments. A game about military conflict with little forward planning and no long-term investments would be a game of tactics rather than strategy, because it would probably be more about maneuvering units on the battle field. To sustain a level of strategic interaction, a game’s internal economy needs to be more complicated than the internal economies that simply complement the physics of an action game. Economies in strategy games usually involve multiple resources and involve many feedback loops and interrelationships. Setting up an economy like that for the first time is challenging, and finding the right balance is even more difficult. As a designer, you need to understand the elements of the economy and develop a keen sense to judge its dynamic effects. Even if you have years of experience, it is easy to make mistakes: There have been many tweaks to the economy of games like StarCraft to retain the right balance after players developed new strategies, even after the game had been long published!

Even without a focus on the economics of production (such as StarCraft’s minerals and SCV units), internal economies can add strategic depth to almost any game. In most cases, this involves planning to use the available resources wisely. As already discussed, the economy of chess can be understood in terms of material (playing pieces) and strategic advantage. Chess is not about production, and gaining a piece in chess is unusual. Rather, the game is about using and sometimes sacrificing your material in order to produce as much strategic advantage as possible. In other words, chess is all about getting the most mileage out of your pieces.

You can find something similar in the game Prince of Persia: The Sands of Time. In this action-adventure game, the player progresses through many levels filled with dexterity and combat challenges. Early in the game, the player is awarded a magical dagger that allows that player to control time. If anything goes wrong, the player can use sand from the dagger to rewind time and to try again. This power can also be used during combat, for example just after the player has taken a big hit. In addition, the player can use sand as a magical power to freeze time. This helps when battling multiple enemies. The sand is not limitless, however. The player can rewind time only so often, but fortunately, defeating enemies provides the player with new sand. This means that, in additional to the usual action-oriented gameplay, the player has to manage a vital resource. The player must decide when is the best time to invest some sand. Different players will have different ideas about when they should use their sand. Some will use it more often to help out with combat, while others will prefer to save it for challenging jumping puzzles. In this way, the sand is a versatile resource: Players are able to use it to boost their performance where they need it most.

### Use an Internal Economy to Create Large Probability Spaces

As internal economies grow more complex, the probability space of your game expands quickly. Games with a large probability space tend to offer more replay value, because players will have more options to explore than is generally achievable with a single play-through. Another benefit is that these games can also create a more personal experience, because the performance of players and their choices directly affect what parts of the probability space open up for exploration.

Games that use an internal economy to govern character development, technology, growth, or vehicle upgrades often use an internal currency to provide options to the player. This is a typical gameplay feature found in role-playing games, in which players spend in-game money to outfit their characters and spend experience points to develop skills and abilities. It is also found in certain racing games that allow players to tune or upgrade their vehicles between (or sometimes even during) races. As long as there are enough options and the options present really different solutions to problems encountered in the game, or are otherwise important to the player, this is a good strategy.

When using an internal economy to customize the gameplay, there are three things you need to watch out for. First, in an online role-playing game, if a particular combination of items and skills is more efficient than others, players will quickly identify and share this information, and the economy will be thrown off-balance. Either players will choose only that option, effectively reducing the probability space and creating a monotonous experience, or they will complain that they cannot keep up with players who did. In games like this, it is important to understand that customization features are best balanced by some sort of negative feedback. Role-playing games usually implement many negative feedback mechanisms for this reason: Every time characters gain a level and improved skills, they need more experience points to get to the next level. This effectively works to reduce the differences in levels and abilities and requires more investment from a player for each level earned.

Second, you have to be sure that the probability space is large enough that players do not end up exploring it entirely in one play session. For example, if in a role-playing game players have a rating between 1 and 5 for the attributes of strength, dexterity, and wisdom, and the player can choose which one to increase from time to time, it is generally a poor design decision to require them to upgrade all these attributes to the maximum in order to finish the game. Similarly, if the player has only limited choice over what order to upgrade her attributes, the consequences of those choices are reduced. A good way to include choices that have real consequences is to create choices that exclude each other. For example, players can generally choose only one class for their character in a role-playing game. Each class should have a unique set of different skills and abilities. In Deus Ex, the player is also presented with choices to improve the cyborg character that have gameplay consequences: The player might be forced to choose between installing a module that will render the character invisible for short periods and a special type of subdermal armor that will make the character much more resistant to damage.

Third, you should ideally design your levels in such a way that players can use different strategies to complete them. For example, in Deus Ex, the player can choose to develop a character in different ways. The player can focus on combat, stealth, or hacking as alternative ways of solving the many challenges in the game. This means that almost every level has multiple solutions. This is not an easy balance to strike. If you estimate that the player has managed to upgrade three options before a certain level, you have to take into account that the player upgraded the combat abilities three times, stealth three times, hacking three times, or perhaps all of them once. In Deus Ex, this problem is even more pronounced because all the sources of experience points that you require to upgrade are not renewable: You gain them for progressing and performing certain side quests. Going back to a previous area to harvest some more experience is not an option.

This example illustrates that the levels in games that permit customization must be more flexible, and more general, than in conventional action games, because you don’t know exactly what abilities the player’s avatar will have. Deus Ex Human Revolution contained a flaw: It allowed the players different ways to play the game but only one way to beat the boss characters, which defeated the point of allowing the players to customize their avatars.

### Tips for Economy Construction Games

Games in which the player builds an economy, such as construction and management simulations, tend to have large and complex internal economies. SimCity is a good example. As players zone areas and build infrastructure, they use these building blocks to craft an economic structure that produces the resources they need to increase it even further. Building a game like this requires the designer to assemble a toolbox of mechanics that the player can combine in many interesting ways. This is even harder than designing a complete, functional, and balanced economy yourself. You have to be aware of all the different ways your economic building blocks combine. When successful, playing the game can be very rewarding, because the economy the players build up through play directly reflects their choices and strategies. This is why no two cities in SimCity are alike.

If you are designing an economy construction game, there are three strategies that can help you keep the complexity of your task under control:

• Don’t introduce all the player’s building blocks at once. Construction and management simulations typically allow the player to build something—a farm, factory, or city, for example—out of elementary units, building blocks, that play a role in the economy. (In SimCity, these are zoned land and specialized buildings.) It is a good idea to gently introduce players to the different elements in your game, a few at a time. This makes it easier to control the probability space, at least initially. By allowing certain building blocks and disallowing others, you can craft scenarios and create special challenges. If your game has no distinct levels or special scenarios, make sure that not all building options are available from the start. Have players accumulate resources before they can use the more advanced building blocks that unlock new options. Civilization is an excellent example of an economy construction game in which most of the building blocks are locked at the beginning of the game and must be unlocked one by one before the players can use them.
• Be aware of the meta-economic structure. In an ideal economy construction game, the number of ways of putting the economic building blocks together is endless. However, in most such games, certain approaches are better than others (and in games with a victory condition, some approaches are unwinnable). As a designer, you should be aware of typical constructions that might be called meta-economic structures. For example, in SimCity, a particular mix of industrial, residential, and commercial zones will prove to be very effective. Players will probably discover these structures quickly and follow them closely. One difficult, but effective, way of dealing with patterns that could become too dominant is to make sure that patterns that are effective early in the game cease to be effective later. For example, a particular layout of zones might be an effective way to grow your population initially but causes a lot of pollution in the long run. Slow-working, destructive positive feedback is a good mechanism to create this sort of effect.
• Use maps to produce variety and constrain the possibility space. SimCity and Civilization wouldn’t be nearly as much fun if you could build your city or empire on an ideal piece of land. Part of the challenge of these games is to deal with the limitations of the virtual environment’s initial state. As a designer, you can use the design of the map to constrain players or to present opportunities. So, although there might be a best way of building the economy (something that we might call a dominant meta-economic structure), it is simply not possible to do so in particular terrain. This forces players to improvise, and rewards players who are more flexible and versatile. In SimCity, the disaster scenarios in which players can unleash several natural disasters on their cities challenges their improvisation and flexibility in a similar vein; and of course, SimCity also generates disasters at random, setting back the player’s progress.