Mechanics Historically How it Evolves --- “Skill Tree” P1

Definition 

“Perks” mechanics is usually treated as the ancestor of “Skill Tree”.  If it is true, then “Skill Tree” derives from “Perks” and develops into a fully configured system.

According to Wikipedia (2013):

A skill tree consists of a series of skills (sometimes known as perks or by other names), which can be earned by the player as he or she levels up or otherwise progresses his or her player character. These skills grant gameplay benefits to the player; for example, giving the character the ability to perform a new action, or giving a boost to one of the character's stats.


This mechanics is called as “tree” for two reasons:
1.    It is tiered
2.    It typically contains multiple paths (choices).

A tiered skill tree means player will need to gain certain level or skill points to unlock different skills (“Perks”). What’s more, player usually needs to achieve all skills in one tier before moving on to the next tier.

On the other hand, in some games, player is allowed to fulfill all the skills from the Skill Tree. However, each player can activate usually only partial of skills.

The following Skill Tree system from World of Warcraft illustrates these two concepts.

Icons in grey are inactive until player complete prerequisites for them (level up the skills to its required level).