[In this article taken from Game Developer magazine, subtitled "A Process for Identifying Low-Risk Design Opportunities", game designer Simon Strange introduces a method for increasing or decreasing player tension in games without altering their fundamental design elements -- a way to tweak a game in order to profoundly change its function.]

All systems are fundamentally in one of three states: growth, decay, or equilibrium.

For a video game, which can be viewed as a system of systems, growth and decay both happen during development. As systems are added, removed, and adjusted, the game more and more resembles its final shape. By the time you ship, your game is (hopefully!) at equilibrium.

Of course, designers cannot simply tweak and tune game systems on a whim. The target equilibrium point (the final state of the game's systems) needs to be identified fairly early on, so that individual systems (and their supporting assets) can be locked down during development. This is a very practical way to reduce risk and manage a project.

Unfortunately, this tends to create an antagonistic relationship between a designer's ability to effect change and the amount of development time left. This reduces the designer's ability to work on game systems during the latter half of the project, which can be very frustrating.

Over the last few years, I've developed a system for identifying and defining low-risk design changes. My goal is to allow design changes during the majority of a project instead of being forced to lock down design elements early on.

By identifying low-risk options in a systematic way, using charts and visual aids (which I discuss in parts 2 and 3), I have been able to describe to producers and publishers in advance exactly why certain changes pose little to no risk to the project's long-term stability. This has afforded me almost twice as much time for fine-tuning our game's core systems, which has resulted in better, and more balanced, more polished products.

Part 1: Defining Tension

The key concept is "equilibrium tension." A system in equilibrium feels the effect of many sub-systems, but each "pull" is balanced by an inverse "pull" of equal magnitude. In the simplest cases, this means two sub-systems opposing one another's effects, but in most cases a combination of sub-systems must be considered. This is exactly analogous to the force diagrams you might have drawn in physics classes.

Imagine a brick resting on a table. The gravitational force on the brick is exactly opposed by the table, so the brick remains in motionless equilibrium. (See Figure 1.) Now imagine your left hand on the left side of the brick. If you press on the brick, the brick will slide to the right. (See Figure 2.) If you use both hands, one on either side, and apply an equal amount of force, you can re-establish equilibrium. (See Figure 3.) The point is that the brick can remain in equilibrium with any magnitude or combination of forces, so long as each force is counteracted by other forces.

This does not mean that all equilibrium states are the same! The "squeezed" brick can absolutely feel the tension from your two hands. In the same way, you can make significantly different experiences within a video game by changing the "tension" on that game's equilibrium state.

Imagine our brick as a playable character in a simple 2D platform game. A player could move the brick left or right, jumping over small obstacles to progress through the world. If the player puts the controller down to take a break, nothing would happen to disturb the brick, just as you might have removed your hands from the physical brick and left it lying on the table.

Now let's add a sub-system, and start throwing fireballs from the right side of the screen every three seconds. The fireballs are a new force which, if unbalanced, would "push" the brick out of equilibrium. To balance this force, the player must simply "push" back by jumping over the fireballs as they appear. So long as the player jumps properly, the game remains in the same equilibrium as before. The difference is that the player is now actively working to balance the game's equilibrium. The more we demand of the player, the more tension we place on our equilibrium state.