In 1968, Charlotte Rude and Hjördis Olsson-Une were two young graduates of Sweden's Konstfack University, where they had studied art and design. The two moved to Älmhult, Sweden, where a glassworks was located; having caught the material exploration bug at design school, the two wanted to experiment with glass.
The pair had very little money and shared an apartment. To furnish it, they bought inexpensive leftover particle board from a nearby construction site, and built pieces they designed themselves.
Älmhult was also where Ikea had opened their first store, back in 1958, and was where their headquarters were based. Some of Rude and Olsson-Une's neighbors worked for Ikea, and when they saw the designers' self-created furniture, encouraged them to try to sell the designs to Ikea. The neighbors introduced them to Ikea manager Gillis Lundgren.
Lundgren didn't buy their designs. Instead he offered them full-time jobs. The duo accepted, and soon began designing furniture.
In 1970s, the Ikea store in Stockholm suffered a fire and needed to be rebuilt. The brass decided they may as well add a large play area for children. The task of designing the play area fell to Rude and Olsson-Une, who were then Ikea's youngest designers. The two designed a sort of indoor playground filled with pillows, ropes and platforms.
But "the biggest star of the play area," according to Ikea, "was the ball pit."
The idea came when Charlotte and Hjördis were opening boxes containing a new type of protective packing material. It consisted of small plastic balls, and reminded Charlotte of the then wildly popular bean bags that kids would sit and lie down in.
They imagined how one could jump and swim around in a sea of balls if it was deep and wide enough. However, these balls were too small. Children might put them in their mouths and choke. At the time, plastic was growing fast as a material, and the young designers soon found lighter and bigger multicoloured balls to use.
A huge wooden box – deep enough to jump into – was built with particleboard and filled with thousands of balls. When the play area opened in 1971, the ball pit became a huge hit. Kids loved it, and families were soon rushing to IKEA to let their children try out the new invention. Later in the 1970s, ball pits of all sorts started popping up in everything from amusement parks to fast-food restaurants, but the ball pit in the Stockholm IKEA store in 1971 was likely the first one in the world.
Rude and Olsson-Une didn't stay at Ikea for long; after just five years, in 1973, they moved to Copenhagen to pursue graduate studies at the Royal Danish Academy of Fine Arts. They took on freelance design work--and apparently faded into obscurity. I can find no record of their work after their time at Ikea.
Artistic representation of a ringing rotating black hole. Credit: Aurore Simonnet (SSU/EdEon).
Observations of gravitational waves produced by 2 black holes colliding and merging have allowed scientists to confirm fundamental predictions made by Albert Einstein and Stephen Hawking about the nature of the universe.
“This is the clearest view yet of the nature of black holes,” says astrophysicist Maximiliano Isi, who co-led the analysis published in the Physical Review Letters.
Cataclysmic cosmological events, such as the merging of 2 black holes, distort the fabric of the universe. This sends out ripples, or ‘gravitational waves’, which stretch and contract space-time.
Gravitational waves produced by merging black holes were first detected by the US National Science Foundation Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2015. LIGO detects changes in space-time smaller than 1/10,000 the width of a proton.
Today, it operates with international partners, the Virgo gravitational-wave detector in Italy and KAGRA in Japan. In January 2025, during LVK collaboration’s current observation run, LIGO picked up on the collision of 2 black holes 1.3 billion light-years away.
“This specific collision involved 2 black holes that looked pretty much identical to the first 2 we saw,” says Isi. “Intrinsically, the signal is equally loud, but our detectors are just so much more high fidelity now.
“We’re able to analyse the signal in ways that just weren’t possible 10 years ago.”
Advancements of gravitational wave observatories in observing black holes cosmic collisions, with registered signals shown comparing the 2015 black hole merger (GW150914) and the one observed in 2025 (GW250114). Credit: Dr Derek Davis (Caltech, LIGO Laboratory).
The researchers studied the event from the moment the black holes first collided, until the merged black hole settled into its new state just milliseconds later.
The final reverberations, or ‘ringdown’, can be likened to the way a bell rings when it is struck.
“Ten milliseconds sounds really short, but our instruments are so much better now that this is enough time for us to really analyse the ringing of the final black hole,” Isi says. “With this new detection, we have an exquisitely detailed view of the signal both before and after the black hole merger.”
This allowed the team to calculate the mass and spin of the black hole to determine its surface area. They found that while the initial black holes had a total surface area of 240,000km2, this increased to about 400,000km2 after merging.
The observations confirm a foundational idea proposed by British physicist Stephen Hawking in 1972, which predicts that the surface area of a black hole’s event horizons can never decrease.
Hawking’s area theorem – also known as the second law of black hole mechanics – mirrors the second law of thermodynamics, which says that entropy (disorder) can only increase. The theorem led to the realisation that black holes are thermodynamic objects.
“It’s really profound that the size of a black hole’s event horizon behaves like entropy,” Isi says.
“It has very deep theoretical implications and means that some aspects of black holes can be used to mathematically probe the true nature of space and time.
“It tells us that general relativity knows something about the quantum nature of these objects and that the information, or entropy, contained in a black hole is proportional to its area.”
The researchers also confirmed that the merged black hole was consistent with what is known as the ‘Kerr metric’.
Left panel: Frequency and decay time (half-life) of the different ‘ringdown’ tones measured in the 2025 black hole merger (GW250114). The black markers indicate the values predicted for a Kerr black hole. Right panel: gravitational-wave signal (bottom spiral) emitted by the remnant black hole (bottom sphere) into the different tones, for a numerical simulation matching the measured parameters of GW250114. Credit: Dr. Keefe Mitman (Cornell University), Prof. Harald Pfeiffer (Albert Einstein Institute, Potsdam).
In 1963, New Zealand mathematician Roy Kerr solved Albert Einstein’s field equations of general relativity and showed that black holes can be described by just 2 characteristics: spin and mass.
“We’ve found some of the strongest evidence yet that astrophysical black holes are the black holes predicted from Albert Einstein’s theory of general relativity,” says Isi.
“Two black holes with the same mass and spin are mathematically identical. It’s very unique to black holes.”
Gravitational wave detectors are only expected to become more sensitive in the next decade, which will allow for even more rigorous tests of black hole characteristics.
“Listening to the tones emitted by these black holes is our best hope for learning about the properties of the extreme space-times they produce,” says astrophysicist Will Farr, who co-led the research.
“As we build more and better gravitational wave detectors, the precision will continue to improve.”
As a developer with a passion for state machines, I’ve often found myself inspired by articles like “A Complete State Machine Made with HTML Checkboxes and CSS.” The power of pure CSS-driven state machines intrigued me, and I began to wonder: could I create something simpler, more interactive, and without the use of macros? This led to a project where I built an elevator simulation in CSS, complete with direction indicators, animated transitions, counters, and even accessibility features.
In this article, I’ll walk you through how I used modern CSS features — like custom properties, counters, the :has() pseudo-class, and @property — to build a fully functional, interactive elevator that knows where it is, where it’s headed, and how long it’ll take to get there. No JavaScript required.
Defining the State with CSS Variables
The backbone of this elevator system is the use of CSS custom properties to track its state. Below, I define several @property rules to allow transitions and typed values:
These variables allow me to compare the elevator’s current floor to its previous one, calculate movement speed, and drive animations and transitions accordingly.
A regular CSS custom property (--current-floor) is great for passing values around, but the browser treats everything like a string: it doesn’t know if 5 is a number, a color, or the name of your cat. And if it doesn’t know, it can’t animate it.
That’s where @property comes in. By “registering” the variable, I can tell the browser exactly what it is (<number>, <length>, etc.), give it a starting value, and let it handle the smooth in-between frames. Without it, my elevator would just snap from floor to floor, and that’s not the ride experience I was going for.
A Simple UI: Radio Buttons for Floors
Radio buttons provide the state triggers. Each floor corresponds to a radio input, and I use :has() to detect which one is selected:
--abs gives the absolute number of floors to move.
--relative-speed makes the animation slower when moving across more floors.
So, if the elevator jumps from floor 1 to 4, the animation lasts longer than it does going from floor 2 to 3. All of this is derived using just math expressions in the CSS calc() function.
Determining Direction and Arrow Behavior
The elevator’s arrow points up or down based on the change in floor:
While the delay runs, the --previous value lags behind the --current-floor. That lets me calculate direction and speed during the animation. Once the delay ends, --previous catches up. This delay-based memory trick allows CSS to approximate state transitions normally done with JavaScript.
Floor Counters and Unicode Styling
Displaying floor numbers elegantly became a joy thanks to CSS counters:
The \278A to \2783 characters correspond to the ➊, ➋, ➌, ➃ symbols and give a unique, visual charm to the display. The elevator doesn’t just say “3,” but displays it with typographic flair. This approach is handy when you want to go beyond raw digits and apply symbolic or visual meaning using nothing but CSS.
Accessibility with aria-live
Accessibility matters. While CSS can’t change DOM text, it can still update screenreader-visible content using ::before and counter().
This keeps the experience inclusive and aligned with accessibility standards.
Practical Applications of These Techniques
This elevator is more than a toy. It’s a blueprint. Consider these real-world uses:
Interactive prototypes without JavaScript
Progress indicators in forms using live state
Game UIs with inventory or status mechanics
Logic puzzles or educational tools (CSS-only state tracking!)
Reduced JavaScript dependencies for performance or sandboxed environments
These techniques are especially useful in static apps or restricted scripting environments (e.g., emails, certain content management system widgets).
Final Thoughts
What started as a small experiment turned into a functional CSS state machine that animates, signals direction, and announces changes, completely without JavaScript. Modern CSS can do more than we often give it credit for. With :has(), @property, counters, and a bit of clever math, you can build systems that are reactive, beautiful, and even accessible.
If you try out this technique, I’d love to see your take. And if you remix the elevator (maybe add more floors or challenges?), send it my way!
If you're like me, you don't love the ergonomics of writing long text
messages on your mobile phone keyboard. We own an “Arteck HB066”
Bluetooth keyboard for this use-case which works great and costs $45.
But I'm not interested in spending money today.
What if
I could write text messages, both SMS or iMessage, using any computer keyboard?
This little tool does just that: write text messages in
this browser window, and it'll generate a QR code which you can scan with your phone camera to send the message.
If you are sending to multiple recipients, use a comma (,) to delimit the different recipient
phone numbers. I recommend using international codes (+1 for the USA), but it appears to work at least on iOS without them.
Don't know or don't want to type in your recipient phone number directly? Add a 1 as the recipient, scan the QR code,
and then fill in the recipients on your phone to use auto-complete from your contacts list.
All data stays within the browser: your data is not processed, saved, or sent to
any other server. If this tool is useful: bookmark the page for later use and let me know what you think.
QR codes generated using qrcode-svg, licensed MIT and Copyright (c) 2020 datalog.
In America, the phrase "Now we're cooking with gas" was slang for "Now we're really operating efficiently."
It originated as a marketing slogan in the 1930s, created by the American Gas Association to push newfangled gas-fired ranges and ovens. And back then, gas stoves were indeed a step up from its predecessor: The wood-fired stove.
Times have changed. We now know that "cooking with gas" could be likened to "playing with fire," in terms of our health. "You wouldn't stand over the tailpipe of a car breathing in the exhaust from that car. And yet nearly 50 million households stand over a gas stove, breathing the same pollutants in their homes," Rob Jackson, an environmental scientist at Stanford University and lead author on a study on pollution from gas cooking, told Food Manufacturing. Gas stoves release pollutants like nitrogen dioxide, which is linked to asthma, and benzene, which is linked to cancer.
Gas stoves can also be a hassle for those who live in cities. Imagine an entire apartment building filled with gas stoves. If a gas leak is detected, as happens a lot—U.S. fire departments are called to some 125,000 residential gas leaks each year—gas to the entire building must be shut off while the problem is addressed. No one in the building can cook until it's fixed—and that can literally take months.
Electric stoves emit no fumes and are more efficient, with up to 80% of the heat generated reaching the target pots and pans. (Gas stoves waste about 50%.) Induction stoves are better still; since they only heat the surface that contacts the pot, their efficiency is around 90%.
The main hassles of switching to an electric or induction stove are the higher cost of the units, and the added expense of retrofitting them. Electric and induction stoves require 240V outlets, higher-amperage breakers and new wiring, which means you've got to hire an electrician to get into the walls.
Now a California-based company called Copper has solved at least one of those problems. They've designed Charlie, a revolutionary induction stove that comes with a battery. Why? Because you can plug it into a regular 120V outlet, no rewiring necessary. The battery draws power at night, when electricity costs are cheaper; when it's time to cook during the day, Charlie's got all the juice it needs. It can run all four burners and the oven at the same time.
The problem Copper hasn't yet solved is the cost. Charlie runs six grand, about double what you'd pay for a high-end electric or gas stove. Hopefully those costs will come down over time.
Even with the high price tag, the company has managed to strike a deal with the NYC Housing Authority to deliver 10,000 units. Clean-energy government incentives—which will probably go away under the new administration—brought the price down to $3,200 per unit at the time the deal was struck. The Charlie units will be a boon for building managers who don't want to deal with gas hassles and don't have the budget to retrofit every apartment's kitchen with 240V.
One challenge with installation I should mention is, the battery-laden Charlie units are extremely heavy, at over 350 lbs. (Electric or gas stoves usually weigh less than half that.) For the sake of the installers, hopefully they're going into elevator buildings.
Ryobi is not exactly the Cadillac of cordless tools, but one still has certain expectations when buying a product. For most of us “don’t randomly stop working” is on the list. Ryobi 18-volt battery packs don’t always meet that expectation, but fortunately for the rest of us [Badar Jahangir Kayani] took matters into his own hands and reverse-engendered the pack to find all the common faults– and how to fix them.
[Badar]’s work was specifically on the Ryobi PBP005 18-volt battery packs. He’s reproduced the schematic for them and given a fairly comprehensive troubleshooting guide on his blog. The most common issue (65%) with the large number of batteries he tested had nothing to do with the cells or the circuit, but was the result of some sort of firmware lock.
It isn’t totally clear what caused the firmware to lock the batteries in these cases. We agree with [Badar] that it is probably some kind of glitch in a safety routine. Regardless, if you have one of these batteries that won’t charge and exhibits the characteristic flash pattern (flashing once, then again four times when pushing the battery test button), [Badar] has the fix for you. He actually has the written up the fix for a few flash patterns, but the firmware lockout is the one that needed the most work.
[Badar] took the time to find the J-tag pins hidden on the board, and flash the firmware from the NXP micro-controller that runs the show. Having done that, some snooping and comparison between bricked and working batteries found a single byte difference at a specific hex address. Writing the byte to zero, and refreshing the firmware results in batteries as good as new. At least as good as they were before the firmware lock-down kicked in, anyway.
He also discusses how to deal with unbalanced packs, dead diodes, and more. Thanks to the magic of buying a lot of dead packs on e-Bay, [Badar] was able to tally up the various failure modes; the firmware lockout discussed above was by far the majority of them, at 63%. [Badar]’s work is both comprehensive and impressive, and his blog is worth checking out even if you don’t use the green brand’s batteries. We’ve also embedded his video below if you’d rather watch than read and/or want to help out [Badar] get pennies from YouTube monetization. We really do have to give kudos for providing such a good write up along with the video.
Log in
