It looks nice. Some tricky questions:

In the first video, at 1:50 someone is writing in a screen that looks like a page with rows[1]. Can I change the distance between the rows? Can I use a graph paper[1] or plotting paper[1]? Can I remove the lines after I made a draw?

It uses a special pen. Where do you store it while you are not using it?

[1] I'm from Argentina, so I speak Spanish. I'm not sure about the translation of the name of the different pattern of the lines that you can have in a paper sheet. We call them, "hoja con renglones", "hoja cuadriculada" y "hoja milimetrada". I tried with autotranslation and some other trick with Google, but I'm not sure that I got the correct translation.