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User Interface Design. CIS 487/587 Bruce R. Maxim UM-Dearborn. Desirable Properties for Game User Interfaces. Attractiveness Graphics, sound, animation, etc. Usability Easy to learn Easy to use Related to playability
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User Interface Design CIS 487/587 Bruce R. Maxim UM-Dearborn
Desirable Properties for Game User Interfaces • Attractiveness • Graphics, sound, animation, etc. • Usability • Easy to learn • Easy to use • Related to playability • Usability is no longer an art and there are technical solutions to usability problems
Work vs Fun • Work is less productive if software is really hard to use • Games are not fun unless some difficulty is involved • A button marked “solve the problem” • Great for work • Worst possible game design
Wrong Ideas • Usability is not an issue for games, they are supposed to be challenging • User can do whatever they want in games, so there are no goals • If sales are good the UI must be OK • No one is complaining, therefore there are no problems
Technical Usability • It is not a matter of opinion or a list of things you are supposed to do • Usability means easy to learn and easy to use • If a system is hard to learn or hard to use, customers will eventually switch to other products
Developing Usable Games • Write out the entertainment goal • What makes the game entertaining? • What needs to be difficult to make it fun? • Identify difficulties that are not part of the entertainment goal and “fix” them using standard usability design concepts
Usability Design Process - 1 • Perform a task analysis • What does the user need to do? • Identify what the user really wants to do (goals not commands) • Choose system functions to support then user’s task • How can the system help the user do the task? (not always obvious)
Usability Design Process - 2 • Set usability targets (e.g. learn basics in 15 minutes) • Choose initial design for chosen functionality • Ease of learning, speed, accuracy • Usability guidelines • Evaluate usability of the design • Correct problems and repeat evaluation until no more problems identified
Principles of Good Design • State and action alternatives are visible • Conceptual model is consistent with system image • Interface should include mappings that reveal relationships among task stages • User should receive continuous feedback
Where is failure likely as users try to accomplish task goals? • Users form inadequate goals • Users fail to find the correct interface object due to poor labeling • Users might not know how to specify or execute a desired action • Users receive poor feedback
Building novel widgets that match user task perceptions • Recognize human diversity • Use 8 golden rules of user interface design • Prevent errors, if at all possible
8 Golden Rules of User Interface Design • Strive for consistency • Enable short-cuts for frequent users • Informative feedback • Design dialogs to yield closure • Offer simple error handling • Permit easy reversal of actions • Support internal locus of control • Reduce short-term memory load on user
Data Display Guidelines • Consistency • Efficient information assimilation by user • Minimal memory load on user • Compatibility between data display and data entry • Flexibility of user control over data display
Getting User’s Attention • Intensity (2 levels only) • Marking (e.g. underscore) • Fonts (up to 3) • Inverse video • Blinking (2 to 4 hertz) • Color (up to 4 standard colors) • Color blinking • Audio
Data Entry Guidelines • Consistency • Minimal user input actions • Minimal memory load on user • Compatibility between data entry and data display • Flexible user control
Factors affecting choice of evaluation methodology • Stage of design • Novelty of product • Expected number of users • Criticality of interface • Cost of product and budget for testing • Experience of design and evaluation teams
Problems with Testing • Can't guarantee perfection • When do stop repairing bugs and ship the prototype? • Testing focuses on normal product use, not extreme
Review Methodologies • Expert Reviews • Usability Laboratory Approaches • Surveys • Acceptance Tests • Evaluation During Active Use • Classical Experimental Psychology
Expert Review Formats • Heuristic evaluation • Guideline review • Consistency inspection • Cognitive walkthrough • Formal usability inspection
Usability Laboratory Approaches • Think aloud • Video tape • Field tests • Destructive testing • Competitive usability testing
Surveys • Focus on specific UI features • Plan statistical analysis before data collection • Consider on-line surveys to increase response rates • Use semantically anchored Likert type scales
Acceptance Tests • Must be based on measurable criteria • Focus on user behavior and task completion
Evaluation During Active Use • Interviews • Continuous user performance data logging • On-line or telephone consulting • On-line suggestion box or trouble reports • On-line bulletin board or newsgroup • User newsletter or conferences
Approaches to User Interface Design • Human Factors: prototype and test • Cognitive theory: production system • Engineering models: • KLM (keystroke level model) • GOMS Models (goals, operators, methods, selection rules)
Keystroke Level Model (KLM) • Choose representative user task scenarios • Specify design to point that keystrokes defining actions can be listed • List keystrokes (operators) required to perform task • Insert mental operators at points user needs to stop and think • Look up standard execution time for each operator • Add up the execution times for the operators • Total is estimated time to complete task
Standard Execution Times • K - key press (0.2 sec = 55 wpm) • P - point with mouse (1.1 sec) • B - mouse button press (0.1 sec) • BB - press and release button (0.2 sec) • H - home hands to keyboard or mouse (0.4 sec) • M - mental act of thinking (1.2 sec)
Inserting Mental Operators: Where does the user stop and think? 1. Initiating a process. 2. Making strategic decisions. 3. Retrieving a chunk from user’s short term memory 4. Finding something on the screen. 5. Verifying intended action is complete.
Mental Operators New vs Experienced Users • New users stop and check feedback after every step • New users have small chunks • Experienced users have elaborate chunks • Experienced users may overlap mental operators with physical operators
1. Initiate delete. (M) 2. Find file icon. (M) 3. Point to file icon. (P) 4. Press & hold button. (B) 5. Verify icon reverse video. (M) 6. Find trash icon. (M) 7. Drag file to trash icon. (P) 8. Verify trash reverse video. (M) 9. Release button. (B) 10. Verify bulging trash icon. (M) 11. Find original window. (M) 12. Point to window. (P) Delete a file by dragging icon to trash 3P + 2B + 7M = 12.6 sec.
Placement of Mental Operators • Hard to do - requires good intuition from designer • Consistency in the number of Mental's assigned is more important than exact positioning
GOMS ModelGoals Operators Methods Selection Rules Advanatges • GOMS models are executable • GOMS models allow simulated execution of user task • Provide a rigorous description of what user must learn • Provide estimate of size or complexity of interface (number of distinct methods and their length) • Can estimate both learning time (about 30 sec per step and execution time (total of KLM operators) • Allow designer to evaluate the effect of reusing or sharing methods among several tasks
This example is extracted from: David Kieras, A Guide to GOMS Task Analysis, University of Michigan Technical Report, Spring, 1994.
User Goals • Delete a file. • Move a file. • Delete a directory. • Move a directory.
To accomplish goal of deleting a file: 1. Accomplish goal of dragging file to trash. 2. Return with goal completed. To accomplish goal of moving a file: 1. Accomplish goal of dragging file to destination. 2. Return with goal completed.
To accomplish goal of deleting a directory: 1. Accomplish goal of dragging directory to trash. 2. Return with goal completed. To accomplish goal of moving a directory: 1. Accomplish goal of dragging directory to trash. 2. Return with goal completed.
Generalized Methods Method for accomplishing goal of deleting an object: 1. Accomplish goal of dragging object to trash. 2. Return with goal completed. Method for accomplishing goal of moving an object: 1. Accomplish goal of dragging object to destination. 2. Return with goal completed.
Sub Method Accomplish goal of dragging item to destination: 1. Locate icon on screen. 2. Move cursor to item icon location. 3. Hold mouse button. 4. Locate destination icon. 5. Move cursor to destination icon. 6. Verify destination icon reverse video. 7. Release mouse button. 8. Return with goal accomplished.
Method for GOMS Model Construction • Make a list of top-level user goals • Write a step-by-step method for accomplishing each goal on list • Continue refining each step that is not a keystroke level operator by defining it as a subgoal and add it to the list of user goals • Continue processing user goals until list is empty (meaning that all user goals are defined in terms of keystrokes) • If there are multiple methods to accomplish a goal supply decision rules to choose which method to invoke
User Interface Styles • Direct manipulation • GUI (graphical user interface) • WIMP (windows, icons, mouse, pull-down menus) • Menus • Forms • Command language
Direct Manipulation Interface Characteristics • Screen objects resemble physical objects • Objects arranged in 2-D space • Trades perceptual motor operations for linguistic operations • Use of recognition in place of recall • Expensive to implement
Direct Manipulation Interfaces Allow • Novices to learn basic fundamentals quickly • Experts to carry out new tasks • Knowledgeable intermittent users to retain operational concepts • Error messages are rarely needed • Users can assess progress to goals and make changes instantly • Users experience less anxiety because systems is understood and actions are reversible • Users gain confidence and mastery through their sense of control over the system
Direct Manipulation Concerns • Increased system resources • Cumbersome actions • Weak macro techniques • History tracing is hard to log • Visually impaired users at risk
GOMS Model for Direct Manipulation Interfaces • Basic goal - minimize learning using a metaphoric device • Basic method - find relevant object on screen and manipulate Step 1. Search screen for an object to operate on Step 2. Select it for manipulation Step 3. Move object on screen to destination
For direct manipulation interfaces you must ensure: • Visual search (steps 1 and 3) works easily to find objects and their destinations • Steps 2 and 3 must be fast consistent and easy to learn • There must be a direct manipulation metaphor or analogy that is familiar to the user (e.g. desktop)
Problems with Direct Manipulation Interfaces • Visual representations are more spread out than simple text - causing "off page" problems • Users must learn meaning of components (e.g. icons) which are meaningful to designer and not user • Visual representation may be misleading • Touch typists do better with a keyboard than with a mouse
Icons • The debate concerning text versus icons is an emotional one. • The usefulness of icons depends on how quickly user can figure out their meanings.
Icon Design Guidelines - part 1 • Represent object/action in recognizable form • Limit number of icons • Make icon stand out from background • Be careful when using 3-D icons • Selected icons must be easily distinguished from unselected icons
Icon Design Guidelines - part 2 • Icons unique from one another • Ensure harmony with family of icons • Design animation movement • Add detailed information if possible • Explore use of icon combinations to create new objects or operations
Components for a Successful Virtual Reality Application • Visual display • Head positioning and sensing • Hand positioning and sensing • Force feedback • Sound input/output • Other sensation • Cooperative and competitive VR requires networking
Menu Architectures • Single • Linear sequence • Tree • Acyclic network • Cyclic network