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August 11, 2008 / Ben Chun

GridWorld Role Play Online

I’m preparing to teach AP Computer Science this fall. One aspect of that preparation was attending the AP Summer Institute for a workshop run by Michael Lew. During that week, one thing we did was walk through a role play written by David Levine and Steve Andrianoff, in which students act out the part of different objects in a simulation of code execution. The code being simulated is from a case study called GridWorld, with which all AP computer science students must become familiar. We pretended to be the students in order to simulate the simulation for ourselves.

As we struggled, flipping around in the pages of our paper scripts and trying to faithfully follow along, I got the idea to convert it all to HTML. This week, I finally did. I was imagining that it would be nice to be able to project this on a screen in front of the class so everyone could at least follow along there.

One major feature of this web version is that you can click method names within the script to go to their page. (Each method has its own page, containing the text from the script.) I have also added return links that use the JavaScript history object to effectively push the “back button” on the browser. As a result, the browser history represents the current call stack for the simulated run of the code. Kinda neat.

One major difference between the web version and the print version is that polymorphic calls (to, say, the act method of a collection of Actors) must be resolved explicitly in order to link to the correct class script — when using paper, this seems to happen implicitly because the individual student representing the called instance knows their own type. It is interesting to think about the possibility of using this difference as a way to further explore polymorphism (and how, exactly, the JVM dispatches method calls) with students.

I welcome feedback from any of you, as beta testers, before I announce this on the APCS list. Here’s the temporary link: Update: GridWorld Role Play Web Version.

The Bug scenario is done, the Critter is not. I’d love to hear about any improvements you think of, things that you find confusing, or other input you might have. If there’s anyone out there who likes the idea, I will finish it up and package it as a .zip file for local use.



Leave a Comment
  1. Ron / Aug 11 2008 1:08 pm


    Looks good. I will try it with my AP CS classes this year. I don’t know how much help I can be, I am working on the yearbook and my alternative teacher certification. I will be able to use it and test it though. Thanks for doing it.


  2. Michael Ferraro / Oct 20 2008 9:45 pm

    This is awesome! I will *definitely* want to use the hyperlink-ified version over the paper version I distributed last year.

  3. Donza / Dec 6 2008 1:15 pm

    I am very interested and will be teaching JAVA with Gridworld in the spring. Your links do not work – will you be fixing them?

  4. Ben Chun / Dec 6 2008 1:24 pm

    Thanks for the heads up … I guess I put the files on my site temporarily but never added them to my CVS repository. Everything should be there now!

  5. Kathryn / Apr 6 2010 4:47 am

    I got very excited when I found this site but the link does not work. Has it been moved to another location?

  6. Ben Chun / Apr 6 2010 9:20 pm

    Hi Kathryn — Thanks for prompting me to repost the files!


  1. GridWorld Role Play Web Version « And Yet It Moves
  2. GridWorld Resources « And Yet It Moves

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