[nitrogen]

I very briefly show some of the interactivity of Ruby+Pry here: https://youtu.be/Gy7l_u5G928?t=805 (the overall code segment starts at https://www.youtube.com/watch?v=Gy7l_u5G928&t=626s)

I'd be happy to hear about better demonstrations, and there's also Pry's website (https://pry.github.io/) where they link to some screencasts.