Stat System

The player stat system is built up in three nested, hierarchical layers. This allows the player to have a choice of micromanaging or macromanaging their characters depending on their play style. It also allows a lot of flexibility on the development side, as new skills can be scripted as needed for specific quests. All values are computed in a bottom-up fashion.

Bottom Tier - Skills
Individual skills that the player can directly use. A new skill can be made up on the spot by quest designers by describing the new skill in terms of other skills and/or parts of the other Tiers, as well defining its place in the other Tiers of the overall stat system. Basic starter skills, ones that all characters get independent of any other stats modified during character creation, are based exclusively on Middle and Top Tier ratings. This makes the basic starter skills the only skills that don't take into account any adjacent Bottom Tier skills.
 * Though Bottom Tier skills can be made up on the spot during scripting, they cannot be made by the player during gameplay. When they are made for general questing purposes during development, they are added to a master list that is available throughout the play-through if the requirements are met. Some Bottom Tier skills have quest requirements themselves, such as having to be taught by a specific NPC.

Middle Tier - Disciplines
This layer consists of generalized categories which individual skills fit into, and are named after different disciplines of study as one would see in a university or vocational school. Individual skill ratings from the Bottom Tier are added up to give overall ratings for their respective disciplines. The discipline with the highest rating is used to determine a character's official title/profession and affects how NPCs address and interact with them. This can be used as checks for quests and conversations, as well as to generally provide a player with a fuller sense of agency and individuality for their character.

Top Tier - Brain/Body
Players will see an overall rating for their character which will be equivalent to their 'level' as in other games. This overall level rating is the sum of the overall Body and Brain ratings. These, in turn, are the sum ratings of their constituent parts.

Brain

 * Frontal
 * Parietal
 * Temporal
 * Occipital
 * Cerebellum

Body

 * Musculoskeletal
 * Cardiovascular
 * Nervous
 * Digestive (?maybe in a 'hardcore' mode for survival?)

Usage Examples
A player finds a broken robot in the wastes. Upon examination, it turns out that some of its circuits have been fried by an EMP. To fix it, the quest designer wants to employ a new skill called "Electrical Engineering." A quest designer may create it by describing it as: Electrical Engineering

[0.5 * Research skill + 0.5 * Hacking skill from Bottom Tier]

[Fits into Engineering Discipline in Middle Tier]

[Requires 50% minimum overall brain rating from Top Tier to be available for use]

Body Augmentation
To get certain body modifications, the player character needs to meet proper Top Tier requirements. These are specific to the augmentation. For instance, ocular implants require a minimum nervous system and occipital lobe rating; Installing or designing augmentations, however, will require additional skill minimums from the Bottom tier.