(First congrats on a great looking project and really good copywriting/teaser.) I think this sort of highly interactive environment is best suited for language

(First congrats on a great looking project and really good copywriting/teaser.) I think this sort of highly interactive environment is best suited for languages without side effects at all. I.e. purely functional language as you see it in a spreadsheet. Allowing any language (JS, Python and so on) gives problems with how to handle errors, show variable values that change over time, how to handle programs that take a long time to evaluate (or never evaluates), how to handle programs that modify the environment (i.e env.x = env.x + 1) and so on.