[Literature] Fundamentals of Game Design, ch 8: User Experience

Rules: be consistent, give good feedback, player should always be in control, few steps to do an action, easy undo/redo, minimize physical stress, no recall, group controls and feedback elements together when they are related, provide shortcuts. No more than 2 clicks between the start/loading screen and actual play.

At all times, the player must be able to answer:

Player question	In-game solution(s)
Where am I?	Minimap, ambient environment sounds
What am I doing right now?	Visual and audio feedback cues
What challenges am I facing?	Quest or mission log
Did my action succeed/fail?	Visual cues
Am I in danger of losing the game?	HP, gauges
What should I do next?	Quest helper

First, define gameplay modes: camera perspective, interaction model (= mapping player input to game actions), and gameplay (= challenges and actions). Then, figure out which visual elements and controls are needed for each UI mode.

Interaction models can be avatar-based (FPS), omnipresent (RTS), party-based (RPG), desktop-like, or contestant (TV game shows).

Solutions for complicated game elements

Solution	Description	Example
Abstraction	Replace a detailed feature by a less accurate one, or aggregate it with another.	Fuel is never seen in racing games
Automation	Let the computer handle the annoying or repetitive parts of a process.	Path finding in RTS is handled by the AI.
Choice of automation	Let the player decide if a feature should be automated or not.	Racing games: manually switching gears is often more efficient than automatic gear.

Broad interface: all buttons are directly on the screen. It takes time to learn and remember where each of them are. Example: plane cockpit.
Deep interface: the information is categorized in hierarchies, menus, and options.
Consoles usually have deep interfaces with menus because there's no mouse pointer and few buttons given to the player. A keyboard, on the other hand, gives a lot of breadth.

The interface should be context-sensitive. Only show the possible actions and buttons in a given situation. Give also visual cues of the consequences. Example: When pointing the cursor to a tree, the pointer should change into an axe.