Ibiyemi Abiodun

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A gamified computer science placement exam GitHub repository

March 2020 to August 2020


Reduct is a game designed to measure the basic computer science skills of incoming CS students. It functions similarly to Scratch, in that instead of typing code, players assemble colourful blocks to create scripts, with the goal of solving simple problems and testing understanding of concepts such as recursion and first-class functions.

It’s based on a similar game of the same name written by Professor Andrew Myers at Cornell, but the version of Reduct that I deployed for this experiment was a complete rewrite of the project in TypeScript. I rewrote the project for a handful of reasons:

The new implementation

Reduct is a complex enough game that rewriting it took a good fraction of the summer. And I had a deadline: the CASE (Cornell Advanced Standing Exam) for computer science students was taking place at the end of the summer, and the game needed to be ready by then for my experiment to work.

To speed things up, I got to work with the tools I was familiar with: namely, React and Redux. Because Reduct is a puzzle game where each move has a predictable impact on the game’s state, it was well-suited to Redux. Every move was implemented as an action or sequence of actions dispatched to the store:

By ditching the canvas in favour of a DOM-based implementation, I could implement most of the game’s logic using simple HTML drag-and-drop events. The trickiest parts were ensuring that the logic of the game was consistent, and adding animations.

The deployment

Each move was logged using Google Cloud logging so that I could see the traces of each session in real time and download the logs in bulk for processing. This turned out to be super valuable when the CASE did roll around, because there were bugs:

Despite a few pretty bad crashes, most of the sessions went off without a hitch, and I ended up with around 90 playthroughs of Reduct to analyze.

The analysis

Unfortunately, this post is going to end on a rather anticlimactic note. In preliminary analysis, this experiment showed a mild positive correlation between Reduct scores (such as time to completion, or number of levels completed) and traditional pen-and-paper CASE scores. However, if there is one thing I hate doing, it is statistics, and I quickly lost my motivation to continue this project now that the software engineering part was over.

As such, I cannot state anything conclusively about whether this game was good for placing students in the appropriate computer science course. Instead, what I gained from this project is:


On this project, I’m grateful for coding assistance from Ian Tomasik and guidance from Professors René Kizilcec, François Guimbrètiere, and Andrew Myers.