Core Mechanics

The core mechanics of a game determine how that game actually operates: what its rules are and how the player interacts with them. It consists of the data and the algorithms that precisely define the game's rules and internal operation. In my book Fundamentals of Game Design, Third Edition (New Riders, 2014), I introduce the concepts of resources, sources, drains, and converters. Much of that material applies specifically to CSGs, which use more kinds of resources than any other genre.

Resources

In many CSGs, the primary resource is money. Money is usually treated as an intangible resource; it is seldom seen in physical form. (Dungeon Keeper is an exception: Gold has to be mined and transported back to a treasury, and the player must expand the treasury when it gets full.)

People are the other major resource in most CSGs. They are above all a source of tax money or labor. Most CSGs simulate people only as workers; children and the elderly don’t contribute to the economy of the game and so are not simulated. What sets people apart from other kinds of resources is that they have feelings: In many games, they have to be kept happy, or they either leave or fail to act as desired. Consequently, managing their happiness becomes a big part of the gameplay, as the earlier section “Simulating Individuals” discusses.

Building materials are generally treated as tangible entities for games that implement the plan-and-build construction mechanic, described earlier. Those that implement the purchase-and-place mechanic don’t need to treat building materials as tangible, and some don’t make building materials a resource at all, going directly from money to constructed objects.

One game series that treats all resources as tangible, including money, is The Settlers from Blue Byte Software. In The Settlers, every kind of resource (and there are many) must be transported from where it is produced either to storage areas or directly to places where it is consumed. Grain, for instance, must be carried from the grain farm to the windmill for grinding; the flour must be carried from the windmill to the bakery; and the bread must be carried from the bakery to the mines, where the miners eat it.

Table 1 lists some resources you commonly find in CSGs and how their sources and drains appear to the player.

Table 1 Common Resources and Their Sources and Drains

The Construction Converter

Construction is a conversion activity that changes labor, money, and materials into buildings (or whatever the CSG constructs). Construction happens only when the player wants it to, so she controls the spending, and she can usually defer construction until such time as she can afford it. Although it drains money (or other materials), the player can see immediately what she gets in return, and in any case, it’s an investment because the constructed object does something useful in the economy.

Drains and Maintenance

A drain is a feature that takes a resource out of the game for good. Decay is the usual drain in CSGs: Buildings or other entities wear out and have to be replaced, which costs money. In SimCity, for instance, the roads wear out and have to be repaved. If the player doesn’t repave them, the sims start to emigrate because they can’t get to work.

The player has to manage the repaving in SimCity personally, but in many games, these maintenance tasks are automated so the player only has to pay for them without actually performing them. Maintenance annoys some players, who would rather buy something once and never have to worry about it again. However, maintenance is an important game balancing tool; it drains resources and prevents the player from building profits endlessly. If you characterize maintenance as an ongoing cost rather than a purchase of assets, it makes more sense. Paying employees is a maintenance cost. You can’t own employees, but you have to pay their wages on a continuing basis; if you stop paying them, they stop working.

You may want to give the player the power to turn off or adjust the level of automatically managed maintenance (and suffer the attendant consequences) so that he can make use of the money for something else that he needs in a hurry. Stronghold 2, a game about managing a medieval castle and its inhabitants, allows the player to set his peasants’ food rations to one of five levels: none, half, normal, extra, and double. With these settings, he can manage the peasants’ food consumption, which is one of the drains in the game.

Disasters

Decay is a continuous drain that the player may or may not have to act upon, depending on whether you allow automatic maintenance. For a more dramatic effect that forces the player to act, you can include disasters. SimCity puts more pressure on the player by having fires, tornadoes, and monster invasions crop up periodically, doing considerable damage. If the player does not take action to repair the damage (which costs money), the city dies, not just through the destruction of buildings, but also through the loss of needed infrastructure such as roads and electrical lines. Disasters need not be natural ones, of course. Stock market crashes or invasion by hostile armies can also be disasters.