- Learnability. The overall learnability for the door code shows a relatively good design. Buttons are clearly marked by their affordances: the protruding design combined with the rubber showcases them as pressable. Moreover, they have signifiers that allow users to gain some informative feedback. Such as lighting up when pressed, and lighting up green or red if a correct or incorrect code has been entered (respectively).
- Safety and Efficiency. Whenever you are entering the door code and realize you’ve made a mistake (which is prone to happen due to the small size of the buttons), there is no way to clear the numbers you’ve entered. Instead, you have to finish entering the four digits, wait for the red light to let you know that the code you’ve entered is incorrect, and then start again from scratch. The main dimensions of usability affected in this case are efficiency and safety. Safety because the door code is prone to errors (small numbers) and offers no good recovery from them, and efficiency because such errors heavily increase the amount of time it takes to open the door.
- Safety Another problem along this approach is lack of proper feedback when entering the door code. Since there is no visual interface, you cannot verify what numbers you have already entered. It has often been the case that I have accidentally pressed two numbers at the same time and I am unsure which one was entered. This also goes in the dimension of safety, as it makes error recovery difficult. Even though the number buttons include lights, that serve as signifiers when pressed, it is easy for one’s finger to cover the view of this signal.
Potential Solution. The main approach to resolve this problem would be to add a visual interface displaying the numbers that have been entered so far. Moreover, adding the functionality to clear all or the last number entered as a button. As an alternative, more simple plan, at the very least adding the functionality of clearing all numbers entered in a single button, even if there is no visual interface. (Deleting the last digit entered would be hard with no visual interface).