1. Pick a design principle or a heuristic that we have discussed in class.

Visibility of system status

2. Find a real‐world artifact (software or physical) that exemplifies well the principle/heuristic you have picked. Include an image (screenshot, photograph) illustrating your point and include a couple of sentences of explanation

The status bar on the door tells the passengers the status of the lavatory, i.e., whether the lavatory is occupied. This design is clever in that no only does the status bar has universal icons and texts on it, it also has different colors for different statuses, with green signaling a “vacant” status and red signaling an “occupied” status. Moreover, the status bar also has a built-in light, allowing passengers to know the status of lavatory in a light-deprived environment, so that when the pilot turns off most of the lights in the airplane during the sleep hours, the passengers will not need to push the door to know whether the lavatory is occupied. This is very important because if one passenger is using the lavatory and another passenger pushes the door, the passenger inside the lavatory will be scared.   

3. Find a real‐world artifact that violates the principle/heuristic you have picked. As before, include an image and a brief explanation to make your point.

I recently bought a coffee thermal mug from a famous cafe. Although it is stylish and able to keep the temperature of what is inside it stable for long, it has a big drawback–I can never know the temperature of the liquid inside the thermal mug by holding the body of the thermal mug, because its material insulates too well. In other words, the status of the water inside the thermal mug is pretty unclear. This drawback has a terrible consequence. That is, I can only know the temperature after I drink what is inside, but that is when it is too late. So far, my tongue has suffered from the heat of the liquid inside the thermal mug for several times. 

4. Show (i.e., present some sort of a sketch, photoshop mockup, etc) illustrating how the artifact from the previous point could be redesigned to conform with the principle/heuristic you have picked. Include a brief explanation.

To add the visibility of the system status to the thermal mug, I believe it is necessary to redesign it by adding two components. The first is a small temperature measuring device inside the thermal mug. The second is a small status demonstrating component next to the mouthpiece of the mug.  The status demonstrating component will show the temperature of the liquid inside in both Celcius and Fahrenheit, so that the users will know clearly about whether the temperature of the liquid inside is too high.