First published in Develop, issue 11 (October 2001)
Every game requires an interface, and although a lot of thought often goes into the design of the main game controls, many overlook the rest of the interface. This article briefly discusses five Golden Rules for basic interface design:
Rule 1: Be Consistent
It sounds obvious but all too many games don't check that their controls maintain their functionality across all contexts, and the result can be a major irritation for players.
Most importantly, ensure that all menus and windows are operated using essentially the same controls. Choose how the players accept a menu option, and how they go back up a menu level, and stick to this convention rigidly.
Rule 2: Minimize Action Depth
The depth of a particular action can be defined as the number of sub-actions required to execute that action. For example, opening a menu by pressing start is at depth 1, quitting a game from the main menu is at depth of 2 (open the main game menu plus select quit).
In general, every action should be at the lowest depth achievable and all common actions should be within a depth of 3 or less. Minimising action depth makes the interface easy to learn and fast to navigate, and will minimize player frustration.
Consider Turok 2's radial weapon select, which is always around depth 1 versus Goldeneye's linear sequence of weapons, where depth increases as you acquire more weapons.
Sidebar: Measuring Action Depth
Any number of systems can be defined for measuring action depth, and your choices of how to do this can affect how you think about the interface design. If we consider selecting to be half an action, and pressing a button or key to be another half action, it is apparent that using a single key to close a window as a shortcut will generally half the depth of exiting the menus when you have finished, for example.
If you add depth for loading times you are more likely to spot the need to include a restart option on the game over screen, so the player doesn't have to reload to play the level again.
Rule 3: Allow Skipping of Non-interactive Sequences
You may want the player to see your expensively rendered cut scene, but they may not care - or they may have seen it a hundred times before, especially if its between a save point and a tough boss. Provide a method to skip cut scenes, but don't use a control the player might hit by accident.
Rule 4: Provide Options - Save Options
Options allow the player to tailor the interface to their own needs. Despite the name, they are not optional to the game design and are a vital part of the interface. Try to allow the player to customise everything that will not affect the core game play.
If the controls can be customised, remember to transfer secondary actions. Black and White, for example, allows you to redefine the control for the move operation (normally on left mouse button) but if you do you lose the double left click function which allows you to jump to a particular location directly.
Also - make sure you save all the options. The player doesn't want to reconfigure every time they start playing the game.
Rule 5: Document It!
Even though most players don't read the manual, they will turn to it if they have a problem, or want to find out if such-and-such a thing is possible. Good documentation will save your players much frustration.
Next month: Golden rules for mainstream interface design.
Golden Rules of Interface Design (Part 2):
Interfaces for a Mainstream Audience
First published in Develop, issue 12 (November-December 2001)
Last month we looked at some basic Golden Rules. This month, we're looking at Golden Rules when designing interfaces for a mainstream audience:
Rule 1: Draw From the Familiar
Don't reinvent the wheel. If there is an interface style already in use that people know about, use that as your starting point. For example, the standard WIMP environment is fine for PC sim games. If you replace it with something else, it had better be easy to learn and offer significant advantages.
The same rule applies to icon design. There are many internationally recognisable symbols you can use to improve the player's immediate comprehension of your interface.
Rule 2: Icons for Speed, Text For Clarity
Icons are great for immediate recognition - provided the player knows what it means. Mainstream players don't generally have the patience of hardcore players so make sure that you provide a text description for all your icons (either as a tooltip, or in a help line somewhere on screen).
The front end for SSX is a good example of using both text and icons to produce a pleasing interface, which is simple to use.
Rule 3: Avoid Overloading Controls
Although it is good to keep the controls down to a minimum, don't be tempted to overload a control. That is, make sure each control has only one meaning. In Jet Set Radio, the interface is beautifully designed except for the overloading of the left trigger, which is used for both camera control and spraying graffiti. This means that you cannot move the camera when you are close to a graffiti tag, which can frustrate many players.
Rule 4: Shortcuts for Advanced Users Only
In PC games, avoid requiring the keyboard for the main interface (with the possible exception of the cursor keys and the space bar). There should generally be some way (no matter how contrived) to achieve an action from the mouse alone. That doesn't mean you shouldn't include keyboard shortcuts as the advanced user will certainly want them, but few mainstream players want to memorize a list of keys before they can play.
On consoles, consider providing an advanced control mechanism that allows the player to achieve certain actions more quickly, such as Goldeneye's ability to trigger mines by hitting the A and B buttons simultaneously. Just make sure that these options are properly documented.
Sidebar: Remembering Shortcuts
A problem with keyboard shortcuts in PC games is that the only sensible key for an action is the letter it begins with - and certain keys go quickly. If you have any action that begins with 'P' you immediately have a problem as this is almost certainly going to be your pause key.
Don't go for some contrived solution such as using the second letters, as this won't help the player at all. Try arranging them in sensible spatial clusters on the keyboard, or renaming the game action so that it can begin with another letter.
Ideally, allow the player to define or redefine their own shortcuts for all the main game actions.
Rule 5: Structure the Learning Curve
Mainstream players can get swamped if you give them all the controls from the start. Introduce the player gradually to everything they can use, ideally within the main game play, but if that's not possible make sure the player is encouraged to play the tutorial before they start play. If your tutorial is as interactive as possible - and the player can skip it or accelerate it - you shouldn't have any problems.