I use a prompt (usually python), which amounts to the same: scratch paper. The nice parts one can copy-paste and edit as needed. Real scratch paper I use only

I use a prompt (usually python), which amounts to the same: scratch paper. The nice parts one can copy-paste and edit as needed. Real scratch paper I use only for drawing angles and lines when dealing with geometry. I recall Donald Knuth stating he programs by sitting next to a big trash bin and writing down all code in pieces of paper, most of which he discards.