story-driven gameplay and linearity

Story-driven gameplay is a way to answer the question of why the players character is doing what he or she is doing.

Linearity is whether the games story goes from A to B to C or allows the player to decide what he or she wants the character to do next.

This can be done in 3 (or possibly more) ways:

• Standalone Actions where the actions don't really affect anything beyond whether for example a quest is done or not (which for quest-chains may affect whether the next quest becomes available but does nothing else).
  
• Boolean Actions where one action may preclude another for some reason (such as there not being enough time to do both).
• Order-Interactive Actions where the order of the actions affect each other (such as doing a quest for NPC A affects how NPC B treats you.
  

These types of actions are on two levels where Standalone actions are the lower, less complex level and Boolean Actions and order-Interactive Actions is on the higher, more complex level.

A game usually includes more then one type of actions. Most actions may be Standalone Actions while Boolean Actions and Order-Interactive Actions are fewer. This both allows a lower complexity for the game as a whole and allows for some interesting interactions where the player have to deal with the consequences of his or her choices.