Strategy Games - Fundamentals of Game Design - page 439

player chooses agriculture and another chooses fishing, each is committed to the
approach she has chosen. However, it will make your game tricky to balance and
will discourage some players. Many players, particularly women, dislike being
forced to make irrevocable decisions whose consequences they do not know.
FIGURE 14.3
Part of the tech tree
from Civilization III .
Prerequisites are at the
left; upgrades progress
to the right.
To design a tech tree, first think of all the upgrades that you would like to intro -
duce in the course of the game. For each upgrade, note whether it applies to a
particular unit, all units of a particular type, all units in the player's forces, or to
the core mechanics generally. Also note what event will trigger the upgrade—the
passage of a certain amount of time, the expenditure of resources, or some other
achievement such as defeating a particular enemy unit or arriving at a certain place
on the map. Once you have an idea of what upgrades you want to include, you can
organize them into a logical sequence or tree; a simple diagram will show which
upgrades lead to which others.
As a general rule, upgrades should strengthen the player's side and give the player
new choices to make. Researching horse breeding, for example, might make cavalry
units available for the first time and thus require the player to start thinking about
how to use them. Don't worry too much about correctly setting the exact cost and
length of time required by each upgrade. Pick some numbers that feel right; you
will undoubtedly modify them during testing.