The player really needs to have input in the game. As much input as possible really. The previous article about AI Assistance in mind, much of this input should be optional as well, but the options should be available.
Input is one of the defining characteristics of a game. Can we simply expose all aspects of the game world to the player? How much is too much?
Remember we’re looking for interesting challenging tasks. Nothing samey. Or are we?
Anyway, once we establish criteria, and once there is a differentiation between good and bad play, are there still choices? What comes after skill? Preference?
A player should be learning something about themselves and the system they are manipulating while playing. Ideally, the system learns about the player as well.
How you win should be important somehow. In fact, one could say that, though games generally have a few win conditions, they should also have many win states.
But what does this all have to do with input? Is input simply exploring the game state-space? How far can player input deviate from perfect input before failure results? Use a golf score, and eschew failure states altogether?
Key presses feel good. Discrete, integer-like, counted.
Analog input has the feeling of effort and finesse.
Vocal input? Image input? Other more complex methods, including constructed scenario keys and SI mindframes?
Secondary layers of input, games often have very few mappings. Movement, destruction, creation are the three most common. Altering objects can also happen (combination of creation and destruction?) and these can be combined in various ways.