Design of Everyday Things [109]
• Cabinets and bottles of medications and dangerous substances deliberately made difficult to open to keep them secure from children.
• Games, a category in which designers deliberately flout the laws of understandability and usability. Games are meant to be difficult. And in some games, such as the adventure or Dungeons and Dragons games popular on home (and office) computers, the whole point of the game is to figure out what is to be done, and how.
• Not the door on a train (figure 7.5).
Many things need to be designed for a certain lack of understandability or usability. The rules of design are equally important to know here, however, for two reasons. First, even deliberately difficult designs shouldn’t be entirely difficult. Usually there is one difficult part, designed to keep unauthorized people from using the device; the rest of it should follow the normal good principles of design. Second, even if your job is to make something difficult to do, you need to know how to go about doing it. In this case, the rules are useful, for they state in reverse just how to go about the task. You systematically violate the rules.• Hide critical components: make things invisible.
• Use unnatural mappings for the execution side of the action cycle, so that the relationship of the controls to the things being controlled is inappropriate or haphazard.
• Make the actions physically difficult to do. require precise timing and physical manipulation.
• Do not give any feedback.
• Use unnatural mappings for the evaluation side of the action cycle, so that system state is difficult to interpret.
Safety systems pose a special problem in design. Oftentimes the design feature added to ensure safety eliminates one danger only to create a secondary one. When workers dig a hole in a street, they must put up barriers to prevent people from walking into the hole. The barriers solve one problem, but they themselves pose another danger, often circumvented by adding signs and flashing lights to warn of the barriers. Emergency doors, lights, and alarms must often be accompanied by warning signs or barriers that control when and how they can be used.
Consider the school door of figure 7.4. Under normal use, this design adds to the safety of the children. But what if there was a fire? Even nonhandicapped adults might have trouble with the door as they rushed to get out. What about short or handicapped teachers—how could they open the door? The solution to one problem—unauthorized exit of schoolchildren—can easily create a major new problem in times of fire. How could this problem be solved? Probably with a push bar located within everyone’s reach on the door, but connected to an alarm so that in normal circumstances it would not be used.
DESIGNING A DUNGEONS AND DRAGONS GAME
One of my students worked for a computer game company helping develop a new Dungeons and Dragons game. He and his fellow students used his experience to do a class project on the difficulty of games. In particular, they combined some research on what makes games interesting with the analysis of the seven stages of action (chapter 2) to determine what factors cause difficulties in dungeon games. 6 As you might imagine, making things difficult is a tricky business. If a game isn’t difficult enough, experienced players lose interest. On the other hand, if it is too difficult, the initial enjoyment gives way to frustration. In fact, several psychological factors hang in a delicate balance: challenge, enjoyment, frustration, and curiosity. As the students reported, “Once the curiosity is lost and the frustration level becomes too high, it is hard to get a person’s interest to return to the game.” All this has to be considered, yet the game must maintain its appeal for players of many different levels, from first-time players to experienced players. One approach is to sprinkle the game with many different challenges of variable difficulty. Another is to have many little things continually happening, maintaining the curiosity motive.
7.5