Monday, April 16, 2018

A Physics Video Game: Kirchhoff's Revenge

I remember the day I came to truly understand the concept of orbit—and why astronauts in the space station seem to be in zero-g, even though they're only 250 miles from Earth's surface, experiencing a gravitational pull close to 90% of what we feel here on Earth. It wasn't during a physics class, or during my time here at PhysicsCentral. I was in my friend's basement, probably 12 years old...playing Super Mario Galaxy.

If you're unfamiliar with the game: it's a 3D take on the classic Nintendo platformer, set in deep space on a series of miniature worlds that the player can jump around and jet between. The game takes advantage of this environment to toy with the player's sense of perspective, featuring puzzles that can't be solved without creative use of gravity and a firm intuitive understanding that "down" is always relative.

But early on in the game, I had one of those "click" moments, the flood of dopamine in your brain that happens when something suddenly makes sense in an intuitive way. Just trying to get a handle on the controls, I took a running leap on a tiny world—and fell over the horizon, landing on the other side of the planet. Shrinking the world down to a size where you can jump far enough to land back where you started suddenly made the concept of orbit astoundingly intuitive: all you're doing is moving laterally fast enough that the planet's surface curves away below you faster than you're falling toward it.

I didn't think too much about it at the time, beyond "Ohhh, cool!"—but experiencing this instant perspective-shift convinced me that video games can be a powerful and engaging tool for teaching. That's part of why, when we had the opportunity to help bring a new physics video game into reality, we jumped at the chance.

Every year, our parent organization (the American Physical Society) doles out tens of thousands of dollars in increments of up to $10k for innovative physics outreach projects, under the banner of our mini grants program. A year or two ago, we got an application from Michigan State professor Gerd Kortemeyer, proposing Kirchoff's Revenge—and now a preliminary version is ready to play, totally free!

If you've taken a few physics classes, you might already have a guess as to what the game's about: Kirchhoff's laws are a well known tool for understanding the behavior of voltage and current in circuits. The player is dropped into a labyrinth of puzzles, where they must assemble larger-than-life circuits—guided by the disembodied voice of a snarky Gustav Kirchoff. (Seriously, he's mean.)

Be prepared to get called "dim" an awful lot.
Image Credit: G. Kortemeyer, et al. Kirchhoff's Revenge
Over the course of the game, the player gets to experiment with the basics of circuitry, constructing series and parallel arrangements of pipes to divide voltages, light up bulbs, short out circuits, and otherwise satisfy the demands of Kirchhoff's omnipresent, distressingly bitter ghost—the overall design, and especially Kirchhoff's voice, gives the gameplay a distinctly steampunk Portal-esque vibe. After a quick playthrough, one of my favorite things about this game is that it touches on the hydraulic analogy between voltage and water pressure by making charges visible as they flow through the "pipes" that make up the game's wires. For all its complexity, electrical engineering is surprisingly similar to plumbing, a fact that can make it less intimidating to students.


Voltmeters installed parallel to a circuit let you see how introducing new circuit elements changes voltage in real-time.
Image Credit: G. Kortemeyer, et al. Kirchoff's Revenge
As a huge fan of that way of thinking about things, I don't feel like the game goes quite as far down that path as it could have; if the batteries in the game were transparent, with little "fans" inside to push or pull the charges along, it might help drive the concept home. In the hydraulic analogy, resistance can be thought of as the "skinniness" of a pipe—and all the "pipe" components in Kirchhoff's Revenge are treated as having effectively zero resistance; it'd be neat to see a narrow resistor-style element other than a bulb introduced. However, water flows faster through narrow pipes, and electrical signals don't travel any faster through a skinny wire—so as it is, the game is more realistic. These are minor quibbles from a physicist, though; they won't detract from the experience if you're picking up the game for a little light fun, and to further your understanding and appreciation of circuitry.

I do worry that the game doesn't do quite enough to explicitly teach the concepts that lie at its core, relying on blackboard diagrams left up around the levels to give the players the clues they need. However, having learned these rules in a classroom setting not that long ago, I have a hard time telling; if you're using the game as a learning tool, leave your perspective in the comments! Is it too easy? Too hard?

The game is still in a relatively early stage, and future versions will include additional elements and more—so check back and give the game another play when development is complete some time in 2019! Due to some hiccups in the mini grant process, Kortemeyer had to create the game with funding from other sources, but the mini grant program's contributions are going to support the creation of new levels, new circuit elements, and smoother, more optimized gameplay. (Before you say it in the comments: yes, we've spoken with Dr. Kortemeyer about the steampunk drone's voice. Yes, it will be gone in future versions.)

Whether you're a physics fan looking to brush up on your circuitry or a teacher looking for a way to reach students that don't seem engaged, Kirchhoff's Revenge might be just what the professor ordered. The game can be downloaded via Steam at the link above—or if you don't have Steam, you can also find it at Dr. Kortemeyer's page on the Michigan State website.

—Stephen Skolnick

PS: Got a creative idea for a physics outreach project based in the United States? You can get funds from APS and the NSF to build a colossal smoke ring cannon, or put muon detectors in surprising places, or do science demos at the mall! A guide to applying can be found here—creative proposals are encouraged!

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