I see I didn't phrase it clearly as a question: So, apart from images:

In what way can I represent mathematical formulas in pubcoder?

I am very interested in a notepad, so that the user can take notes with a digital pencil while reading.

You can already use the drawing game without picture,
but the pens there are clearly for drawing, not writing or taking notes.
Is there a better option I am missing
or an option to change the marker to a pencil etc.?

Hey, i am a math teacher and look for a way to show formula.
Great would be KaTeX or LaTex, but i am glad about any kind of possibility.
Keep up the good work.