Game Design the Wrong Way

Opportunity cost is a very simple concept.  The opportunity cost of any action is any other actions that are then precluded.

If I have one hundred dollars, and I use it to buy a bicycle, the opportunity cost of that purchase is all of the other things that I could have purchased with that hundred bucks.

When looking at games, and specifically decisions within games, it’s a useful concept, as thinking about the opportunity cost of a decision can help us define what the actual decision is at any point.

If a decision has no opportunity cost, then it’s not a decision.  This is rare - usually, even *not* doing somehting is a viable alternate, and so the opportunity cost of any action is, generally, that you lose the ability to not perform the action.

As an example, if casting a particular spell is free, and that spell has some lasting effect on the player, then the opportunity cost of casting that spell is *not* having that effect on you.

For another example of how thinking about opportunity cost can help in game design, let’s look at RTS games.  In a typical RTS game, you will have some type of gatherer unit that collects resources.  A typical decision early in most games, is whether the player should build more gatherer units, start building offensive units, or start building defensive units.

Any of these choices does not preclude you performing the others in the future.  Building production units at the immediate moment doesn’t stop you from building offensive or defensive units later - in fact, it makes it easier.  In many games, you could actually, to some extent, build all three at once.

So, what’s the effect of building production units early?  You get an early boost to your economy that (generally) will give you an early bonus in production, assuming that you live long enough to see it.  Similarly, early production of offensive units gives you the ability to do an early attack before your opponent has had a chance to build any defense, and early production of defensive units will defend your base against an early attack.

When you look at these three choices, the traditional 3 early game strategies (expand, rush, defend) become very obvious.  The opportunity cost of “early production” is early defense and offense - you become vulnerable to an opponent doing an early attack.  The opportunity cost of early defense is production and offense - you can’t take advantage of your opponent if they don’t defend early, and you lose any production boost you could use against a defensive opponent.  The opportunity cost of early offense is that you don’t get the production boost, and are still vulnerable against early attacks (although you can meet the opposing force head-on and at least have a chance).

Another interesting place to look at opportunity cost is MMO abilities.  In typical MMOs, abilities have sufficiently long reuses that casting a spell or using an ability does not, in any meaningful way, preclude using the other abilities.  And, with the generally slow regeneration of power, abilities usually don’t cost enough power for power to be a truly first-tier consideration in what you should do.

So, what’s the opportunity cost?  Generally, it seems to be tied to a few things:

1. Time to execute the ability.  Since, in most MMOs, abilities hav an execution time that prevents you from doing other activities, the opportunity cost of an ability is the fact that while it prevents you from doing other things during that time.
2. Side effects of the ability.  Casting a large, damaging spell may have side effects such as angering the opponent so that it will attack you.  In many cases, this is undesirable.
3. Abilities that are mutually exclusive.  This is often seen in “stances” that some classes can take which are mutually exclusive, but it can also be seen in spells where a spell can prevent another type of spell from being cast on the same target, either offensively or beneficially.
4. Power can be a consideration, as it can prevent you from casting other spells, but this usually happens later in the fight (especially when things have already taken a bad turn)

BTW, opportunity cost is an economic term, and you’ll be seeing a lot of things from economics in this blog over time.  Mathematical game theory is often used in economics, and games are often about resoure allocation, which is, in many ways, what economics is about.