[How do you make your game UI more usable? Developer Glinert looks at the four main elements -- learnability, simplicity, efficiency, and aesthetic -- that help game usability to flourish.]
A common gripe I hear from developers is that a game has a really great concept or aesthetic, but that the user interface (UI) is lousy. Games that are hard to control or that mystify users by not providing useful or sufficient feedback are pretty damn frustrating to play. This can translate into worse sales, so it's worthwhile for game developers to really spend a lot of time thinking about a game's UI.
How are great UIs created? Certainly experience and good instincts are necessary to create a UI which is both highly functional and aesthetically pleasing. It is also helpful to have concrete methods for analyzing usability, and in this article I'll define and focus four dimensions of usability: Learnability, Simplicity, Efficiency, and Aesthetic.
The purpose of defining such usability dimensions is to provide a methodology for talking about UIs, i.e. user interface X is more learnable, but less efficient, than user interface Y. Keep in mind that these dimensions are not a rating of how "good" a UI is, as sometimes it makes sense to disregard certain principles for the sake of gameplay. What's important is in these cases the game developers are conscious of such choices, and that they are not decided arbitrarily.
This dimension mainly concerns novice users. Most developers prefer straightforward UI learning. To this end, tutorials are commonplace, as they provide a safe environment for learning controls and mechanics while providing meaningful assistance and guidance.
Once learned by the player, use of the UI should be based on recognition rather than recall. Generally one should not be expected to remember every game control, rather there should be easily accessible reminders where appropriate.
The exception to this rule comes from games where learnability is part of the game mechanic. The fighting genre is the most regular example of this exception, as players are rewarded for learning difficult-to-remember controls.
For instance, in Street Fighter II discovering the input sequence for a Hadouken (or any of the other complex moves in the game) is generally quite hard to learn from experimentation, but once it is found the player is rewarded with a new fun skill.
Street Fighter II has learnability at the core of its game mechanic, as players must learn complicated input sequences for attacks.
Even within fighting games there is a hidden learnability method -- namely, feedback. Obvious, immediate, and repeatable feedback between input and output are critical for learnability, and thus trial and error in a fighting game will likely teach the user much about the mechanic. Relying only on feedback is dangerous, though -- how will users learn non-obvious or complicated input methods? Perhaps more importantly, will such a game be fun for someone who has yet to learn these expert inputs?
Learnability also dictates that controller mappings should be consistent; if the X button is used for "yes" in one area of a game, it should always be used for confirmation throughout. This is why this sort of consistency is made part of the standards set by the console manufacturers.
Likewise, controls should match real world expectations; if most other games in a genre have X as the standard button for "yes", then a new game within that genre should conform for maximum learnability. Games with highly learnable interfaces are inviting to new users as they tend to be easy to pick up and play, while novel user interfaces frequently have difficult learnability issues as all users are effectively novices. Remember how tricky it was playing Guitar Hero for the first time?
 This list is based on Rob Miller's dimensions of HCI usability, but only focuses on the four that are especially relevant to video games. For more information on usability dimensions I'd recommend references from design experts like Jakob Neilson, Donald Norman.
 However one must be wary of slavish adherence in the face of new, superior control schemes.