I had two of my friends try the project during user testing. While conducting the test, I connected the p5.js sketch to the Arduino, displayed the sketch in full screen, and left the users to determine how to interact with both the box and the screen. Even though they were mentioned in the instruction that was displayed on the screen, users were uncertain about interacting with the box and screen simultaneously. So I needed to explain that they would receive hints on the screen and input the code using the button and knob on the box.
About the guessing the code, they quickly understood how to use the hints to guess the three digits required to unlock the code. However, they found it confusing regarding how to backtrack and edit an entered code if they wanted to change one of the digits, which is not possible in the game. And that was missing in the instruction.
In this vide the user is trying to crack the code for the second time: https://youtube.com/shorts/YVequMRq7eI?feature=shared
After user testing, I decided to add instructions on how to enter the code and clarify that editing the already entered code was not an option. Also, I chose to include printed instructions on the box, indicating users should gather hints from the screen to input the digits accordingly.