## Wednesday, August 23, 2017

### Reviving the Living Paper Project

A very long time ago, I wrote some computer programs to go with my price theory textbook. The idea, in each case, was to do something on the computer that could not be done on paper. My favorite was a program I called curvedraw, which let you draw a total cost curve freehand on the computer. As you did so, the computer drew the corresponding marginal cost and/or average cost curves. At any point you could switch from drawing total cost to drawing one of the other two, at which point the computer would take over drawing the total cost curve. You could click on any part of the total cost curve and have the program draw a tangent with horizontal length one, hence vertical length equal to the slope, i.e. the marginal cost, thus seeing visually why the marginal cost curve was what it was. The idea was to teach the student to intuit the relation between total, marginal and average, between a function, its derivative, and its average.

My plan was to produce more programs and offer to customize them to other textbooks, and I sketched out ideas for some of them. I also had a design for a computer game in which the player was  building a trade league, an "empire" based not on conquest but on mutual advantage. An early version was written  by a programmer friend of mine but the living paper project eventually died, since neither I nor my friend was willing to put enough time and effort into it.

I put up a description of the project a few years ago, in the hope of bringing it back to life as open source. That may now be happening.  Ricardo Cruz has been looking at doing my programs in javascript so that anyone could try them using the browser. He has asked me to announce the mailing list [1] and the github page [2]: