# Tetris Goes Full Circle

As a game concept, Tetris gave humanity nearly four solid decades of engagement, but with the possibility for only seven possible puzzle pieces it might seem a little bit limiting. Especially now that someone has finally beaten the game, it could be argued that as a society it might be time to look for something new. Sinusoidal Tetris flips these limits on their head with a theoretically infinite set of puzzle pieces for an unmistakable challenge.

Like Tetris, players control a game piece as it slowly falls down the screen. Instead of blocks, however, the game piece is a sinusoid that stretches the entire width of the screen. Players control the phase angle, amplitude, and angular frequency in order to get it to cancel out the randomly-generated wave in the middle of the screen. When the two waves overlap, a quick bit of math is done to add the two waves together. If your Fourier transformation skills aren’t up to the task, the sinusoid will eventually escape the playing field resulting in a game over. The goal then is to continually overlap sinusoids to play indefinitely, much like the original game.

While we’re giving Tetris a bit of a hard time, we appreciate the simplicity of a game that’s managed to have a cultural impact long after the gaming systems it was originally programmed for have become obsolete, and this new version is similar in that regard as well. The game can be quite addictive with a lot to take in at any given moment. If you’re more interested in the programming for these types of games than the gameplay, though, take a look at this deep-dive into Tetris for the NES.

# Blender And OpenEMS Teamed Up Make Stunning Simulations

There’s tons of theory out there to explain the behavior of electronic circuits and electromagnetic waves. When it comes to visualization though, most of us have had to make do with our lecturer’s very finest blackboard scribbles, or some diagrams in a textbook. [Sam A] has been working on some glorious animated simulations, however, which show us various phenomena in a far more intuitive way.

The animations were created in Blender, the popular 3D animation software. As for the underlying simulation going on behind the scenes, this was created using the openEMS platform. [Sam] has used openEMS to run electromagnetic simulations of simple circuits via KiCAD. From there, it was a matter of finding a way to export the simulation results in a way that could be imported into Blender. This was achieved with Paraview software acting as a conduit, paired with a custom Python script.

The result is that [Sam] can produce visually pleasing electromagnetic simulations that are easy to understand. One needn’t imagine a RF signal’s behaviour in a theoretical coax cable with no termination, when one can simply see what happens in [Sam]’s animation.

Simulation is a powerful tool which is often key to engineering workflows, as we’ve seen before.

# Duality Of Light Explored By Revisiting The Double-Slit Experiment

We’ve all seen recreations of the famous double-slit experiment, which showed that light can behave both as a wave and as a particle. Or rather, it’s likely that what we’ve seen is the results of the double-slit experiment, that barcode-looking pattern of light and dark stripes, accompanied by some handwaving about classical versus quantum mechanics. But if you’ve got 20 minutes to invest, this video of the whole double-slit experiment cuts through the handwaving and opens your eyes to the quantum world.

For anyone unfamiliar with the double-slit experiment,  [Huygens Optics] actually doesn’t spend that much time explaining the background. Our explainer does a great job on the topic, but suffice it to say that when coherent light passes through two closely spaced, extremely fine openings, a characteristic pattern of alternating light and dark bands can be observed. On the one hand, this demonstrates the wave nature of light, just as waves on the ocean or sound waves interfere constructively and destructively. On the other hand, the varying intensity across the interference pattern suggests a particle nature to light.

To resolve this conundrum, [Huygens] jumps right into the experiment, which he claims can be done with simple, easily sourced equipment. This is belied a little by the fact that he used photolithography to create his slits, but it should still be possible to reproduce with slits made in more traditional ways. The most fascinating bit of this for us was the demonstration of single-photon self-interference using nothing but neutral density filters and a CCD camera. The explanation that follows of how it can be that a single photon can pass through both slits at the same time is one of the most approachable expositions on quantum mechanics we’ve ever heard.

[Huygens Optics] has done some really fascinating stuff lately, from variable profile mirrors to precision spirit levels. This one, though, really helped scratch our quantum itch.

# Audio Processing In Rust

[Michael] volunteers with emergency services, and sometimes has to monitor radio traffic. Sometimes there’s a lot to review, and to make it easier he wrote a noise gate — think of it as a squelch — to break apart recorded audio into parts. Rust has been gaining popularity for writing low level software, and that’s the language he uses. However, you’ll see even if you don’t know Rust, it is pretty easy to figure out.

For test data, [Michael] took some publicly-available recordings of air traffic control. Using some ready-made audio processing functions and a simple state machine makes the code easy to write.

# Create An Aurora Of Your Own

Throughout our day-to-day experiences, we come across or make use of many scientific principles which we might not be aware of, even if we immediately recognize them when they’re described. One such curiosity is that of caustics, which refers not only to corrosive substances, but can also refer to a behavior of light that can be observed when it passes through transparent objects. Holding up a glass to a light source will produce the effect, for example, and while this is certainly interesting, there are also ways of manipulating these patterns using lasers, which makes an aurora-like effect.

The first part of this project is finding a light source. LEDs proved to be too broad for good resolution, so [Neuromodulator] pulled the lasers out of some DVD drives for point sources. From there, the surface of the water he was using to generate the caustic patterns needed to be agitated, as the patterns don’t form when passing through a smooth surface. For this he used a small speaker and driver circuit which allows precise control of the ripples on the water.

The final part of the project was fixing the lasers to a special lens scavenged from a projector, and hooking everything up to the driver circuit for the lasers. From there, the caustic patterns can be produced and controlled, although [Neuromodulator] notes that the effects that this device has on film are quite different from the way the human eye and brain perceive them in real life. If you’re fascinated by the effect, even through the lens of the camera, there are other light-based art installations that might catch your eye as well.

# Theo Jansen Invents A Faster, Simpler, Wind-Powered Strandbeest

[Theo Jansen] has come up with an intriguing wind-powered strandbeest which races along the beach with surprising speed and grace. According to [Jansen], it “doesn’t have hinging joints like the classical strandbeests, so they don’t get sand in their joints and you don’t have to lubricate them.” It’s called UMINAMI, which appropriately means “ocean wave” in Japanese.

There are only videos of it in action to go on so far, but a lot can be gleaned from them. To make it easier to keep track of just a single leg, we’ve slowed things down and reddened one of them in the banner animation. Those legs seem to be providing a push but the forward motion is more likely supplied by the sails. The second video below shows it being pulled along by the type of strandbeest we’re all more used to seeing.

What follows is an analysis and best guess about how it works. Or you can just enjoy its graceful undulations in the videos below.

# Interference Scanner With Clear Instructions

Meticulous. Thorough. Exacting. These are all words we’d use to describe this video by [BrendaEM] about her Homemade 3D Optical Interference Scanner which can be seen after the break. The scanner uses 3D-printed parts and repurposed materials you might find lying around in your spare parts bin. An old optical drive tray acts to move the laser-wielding sled while a stripped-out webcam is an optical sensor. Links to relevant files such as 3D models and Arduino sketches will be found in the video’s author section.

The principle of operation is demonstrated with a water analog in the video at 2:00 with waves in a plastic container. By creating two small apertures between a light source and a sensor, it’s possible to measure the light waves which make it through. [BrendaEM] uses some powerful visualization software to convert her samples into 3D models which look really cool and simultaneously demonstrate the wave nature of light.

On the left side of her device are the control electronics which don’t need any special coatings since light won’t pass over this area. For the right side, where coherent light is measured, to borrow a Rolling Stones lyric: no colors anymore, I want them to turn black. Even the brass strips with apertures are chemically darkened.

Most of the laser hacks here use lasers rather than measure them, like this Laser Clock and a Laser Projector.