Design Pattern: Upgrade

The upgrade is a pattern that is applied all the time to games.  The player is allowed to make a decision to improve a game entity in some way.  Upgrades always cost something to acquire, usually a resource and/or time.

Upgrades come in two flavors: upgrades of course and upgrades of choice.

The former covers upgrades where you will get the upgrade just by playing and often represent an expansion of player skill and game difficulty.  In classic FPS's, like Doom, gaining access to a new weapon as you play through the levels is an example of an upgrade of course.  A more colloquial term for this flavor would be ability curve, where over the course of play (see the name?) the player's abilities expand.  Upgrades of course are useful for in-play tutorials.

The latter is the type of upgrade which pertains to the customization of a game entity.  Usually, upgrades of choice are pigeon-holed in some way; that is, there are more choices of upgrades than there are chances to upgrade, either by a restriction on the number of upgrades or by availability of upgrade resources.  This forces the player to make a choice concerning how they want to improve.  The former type of pigeon-holing is more easy described as expansion slots while the latter is an example of scarcity.

Examples

Age of ... Series

The technologies of the games are upgrades of choice almost universally, though some only grant access to other technologies to be researched.  Researching techs in most games including the Age of ... Series is almost always done with scarcity; you can research everything, but time and resources are scarce enough that you usually have to make decisions.

D&D

As characters progress in D&D (3.0 and later, at least), they are allowed to add Feats to their character.  Feats are special abilities that allow you to break the normal rules in some way, ostensibly because the character has become just that awesome.

There are many many dozens of feats, and no source book or expansion is complete without a list of new feats to make your characters especially over-powered.  Since these are permanent additions to character abilities, they are pigeon-holed upgrades of choice, or expansion slots.


Halo, DOOM, etc.

FPS's almost always use upgrades of course; as you play, you gain access to more types of weapons.  The resource you expend in these situations is usually only the time it takes to play to t a given level where access to a weapon is granted.