Enhancing Questionnaire Experience: Preventing Blank Input, Validating Integers, and Streamlining User Interaction

URL of experiment:

Description of the problem:
I am trying to start my experiment with a series of questionnaires and have found a functional solution. However, I would still like to improve on it if possible. The biggest issue is that people can press continue by accident before giving input. I want to limit it so that people cannot continue if the input is blank.
Additional nice things would be to only allow them to continue if they have inputted an integer (perhaps only in a certain range such as 0-4).
Also, it would be nice if they could press enter rather than having to use the mouse. I have other parts of my experiment where people simply input a simple digit from 1-5 but that won’t work here as I will display Ishihara colourblindness tests that require people to enter 2 digits.

I have looked through this topic which seems to cover similar issues, but either something has changed in psycohpy or else I have just been unfortunate in getting the example to run online (it works locally).

Thanks for reading