[dekhn]

I personally do enjoy sometimes doing written math. I manually matrix-multiplied the three axis rotation functions (see the three one-axis rotation functions, and the result of multiplying them) https://en.wikipedia.org/wiki/Rotation_formalisms_in_three_d...) But of course these days I just let the computer do rotations for me.

I think the interesting product idea here would be something I've never seen: a canvas on a tablet that acts like pencil and paper (drawing) but also "helps" by recognizing what you write, converting it to a formal language, and validating/verifying it. sort of the mathematica notebook, but more like a notepad