doom

96 Articles

Screenshot of Linux in a PDF in a browser

Nice PDF, But Can It Run Linux? Yikes!

February 10, 2025 by 21 Comments

The days that PDFs were the granny-proof Swiss Army knives of document sharing are definitely over, according to [vk6]. He has managed to pull off the ultimate mind-bender: running Linux inside a PDF file. Yep, you read that right. A full Linux distro chugging along in a virtual machine all encapsulated within a document. Just when you thought running DOOM was the epitome of it. You can even try it out in your own browser, right here. Mind-boggling, or downright Pandora’s box?

Let’s unpack how this black magic works. The humble PDF file format supports JavaScript – with a limited standard library, mind you. By leveraging this, [vk6] managed to compile a RISC-V emulator (TinyEMU) into JavaScript using an old version of Emscripten targeting asm.js instead of WebAssembly. The emulator, embedded within the PDF, interfaces with virtual input through a keyboard and text box.

The graphical output is ingeniously rendered as ASCII characters – each line displayed in a separate text field. It’s a wild solution but works astonishingly well for something so unconventional.

Security-wise, this definitely raises eyebrows. PDFs have long been vectors for malware, but this pushes things further: PDFs with computational power. We know not to trust Word documents, whether they just capable of running Doom, or trash your entire system in a blink. This PDF anomaly unfolds a complete, powerful operating system in front of your very eyes. Should we think lightly, and hope it’ll lead to smarter, more interactive PDFs – or will it bring us innocent looking files weaponized for chaos?

Curious minds, go take a look for yourself. The project’s code is available on GitHub.

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Running Doom On An Apple Lightning To HDMI Adapter

February 6, 2025 by 25 Comments

As a general rule of thumb, anything that has some kind of display output and a processor more beefy than an early 90s budget PC can run Doom just fine. As [John] AKA [Nyan Satan] demonstrates in a recent video, this includes running the original Doom on an Apple Lightning to HDMI Adapter. These adapters were required after Apple moved to Lightning from the old 30-pin connector which had dedicated pins for HDMI output.

As the USB 2.0 link used with Lightning does not have the bandwidth for 1080p HDMI, compression was used, requiring a pretty beefy processor in the adapter. Some enterprising people at the time took a hacksaw to one of these adapters to see what’s inside them and figure out the cause of the visual artifacts. Inside is a 400 MHz ARM SoC made by Samsung lovingly named the S5L8747. The 256 MB of RAM is mounted on top of the package, supporting the RAM disk that the firmware is loaded into.

Although designed to only run the Apple-blessed firmware, these adapters are susceptible to the same Checkm8 bootROM exploit, which enables the running of custom code. [John] adapted this exploit to target this adapter, allowing this PoC Doom session to be started. As the link with the connected PC (or Mac) is simply USB 2.0, this presumably means that sending keyboard input and the like is also possible, though the details are somewhat scarce on this aspect.

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You Can Now Play DOOM In Microsoft Word, But You Probably Shouldn’t

January 20, 2025 by 23 Comments

DOOM used to primarily run on x86 PCs. It later got ported to a bunch of consoles with middling success, and then everything under the sun, from random embedded systems to PDFs. Now, thanks to [Wojciech Graj], you can even play it in Microsoft Word.

To run DOOM inside Microsoft Word, you must enable VBA macros, and ignore security warnings, to boot. You’ll need a modern version of Word, and it will only work on Windows on an x64 CPU. As you might imagine, too, the *.DOCM file is not exactly lightweight. It comes in at 6.6 MB, no surprise given it contains an entire FPS. It carries inside it a library called doomgeneric_docm.dll and the whole doom1.wad data file. Once the file is opened, a macro then extracts all the game data and executes it.

If you think that Microsoft Word doesn’t really have a way of displaying live game graphics, you’d be correct. Instead, that DLL is creating a bitmap image of the game state for every frame, which is then displayed inside Word itself. It uses the GetAsyncKeyState function to grab inputs from the arrow keys, number keys, and CTRL and space so the player can move around. It certainly sounds convoluted, but it actually runs pretty smoothly given all the fuss.

While this obviously works, you shouldn’t get in the habit of executing random code in your word processor. It’s just not proper, you see, like elbows on the dinner table! And, you know. It’s insecure. So don’t do that.

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Nice PDF, But Can It Run DOOM? Yup!

January 15, 2025 by 12 Comments

DOOM is a classic game to implement on a variety of platforms, but doompdf by [ading2210] is one we didn’t see coming. It runs a bit slow and controls are a little awkward but it does run. Entirely within a PDF file, at that.

How is this possible? PDFs are technically capable of much more than just displaying static content, and support JavaScript with their own library of functions. Adobe Acrobat implements the full spec, but modern web browsers implement at least a subset of the functionality in a sandboxed JavaScript runtime environment. Input and output are limited to things one might expect from a fancy PDF form (text input boxes, clickable buttons, things of that nature) but computation-wise, just about anything goes.

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Hackaday Links: January 5, 2025

January 5, 2025 by 4 Comments

Good news this week from the Sun’s far side as the Parker Solar Probe checked in after its speedrun through our star’s corona. Parker became the fastest human-made object ever — aside from the manhole cover, of course — as it fell into the Sun’s gravity well on Christmas Eve to pass within 6.1 million kilometers of the surface, in an attempt to study the extremely dynamic environment of the solar atmosphere. Similar to how manned spacecraft returning to Earth are blacked out from radio communications, the plasma soup Parker flew through meant everything it would do during the pass had to be autonomous, and we wouldn’t know how it went until the probe cleared the high-energy zone. The probe pinged Earth with a quick “I’m OK” message on December 26, and checked in with the Deep Space Network as scheduled on January 1, dumping telemetry data that indicated the spacecraft not only survived its brush with the corona but that every instrument performed as expected during the pass. The scientific data from the instruments won’t be downloaded until the probe is in a little better position, and then Parker will get to do the whole thing again twice more in 2025. Continue reading “Hackaday Links: January 5, 2025” →

Protect Your Site With A DOOM Captcha

January 1, 2025 by 25 Comments

We all know that “Can it run DOOM?” is the first question of a hardware hacker. The 1993 first person shooter from id Software defined an entire genre of games, and has since been made open source, appearing on almost everything. Everything, that is, except a Captcha, those annoying “Are you a human” tests where we’re all expected to do a search giant’s image classification for them. So here’s [Guillermo Rauch] with a DOOM captcha, in which you must gun down three bad guys to proceed.

As a way to prove you’re a human we can’t imagine a more fitting test than indiscriminate slaughter, and it’s interesting to read a little about what goes on behind the scenes. It’s a WebAssembly application as you might have guessed, and while it’s difficult to shake that idea from the early ’90s that you needed a powerful computer to run the game, in reality it shows just how powerful WebAssembly is, as well as how far we’ve come in three decades.

We’d prefer a few different entry points instead of always playing the same level, and we were always more handy with the mouse than the keyboard back in the day, but it’s certainly a bit of fun. It’s worth noting that simply playing the game isn’t enough to verify your humanity — if you’re killed in the game before vanquishing the required three foes, you’ll have to start over. As the game is running at “Nightmare” difficulty, proving your worth might be a tad harder than you’d expect…

Need more DOOM? How about seeing it on hardware nobody would have believed in 1993?

The Business Card Of DOOM

December 28, 2024 by 11 Comments

This account of running DOOM on a PCB business card isn’t really about serving the “Will it DOOM?” meme of getting the classic game to run on improbable hardware. Rather, this project has more to do with getting it done right and leveraging work that’s already been done.

We’ll explain. You may recall [rsheldiii]’s previous DOOM keycap build, which was quite an accomplishment for someone who doesn’t fancy himself a hardware hacker. But he made a fair number of compromises to pull that build off, and rather than letting those mistakes propagate, he decided to build a more general platform to serve as a jumping-off point for the DOOM building community. The card is centered on the RP2040, which keeps things pretty simple. The card has a tiny LCD screen along with USB jacks for power and a keyboard, so you can actually play the game. It also has GPIO lines brought out to pads on the edge of the board, in case you want to do something other than play the game, which is shown in the brief video below.

Pretty standard stuff, right? Perhaps, but where this project stands out for us is that it stresses the importance of relying on reference circuits. We’ve all seen projects that have been derided for pulling the example circuit from the datasheet, but as [rsheldiii] points out, that seems a little wrongheaded. Component manufacturers put a lot of effort into those circuits, and they don’t do it out of the goodness of their hearts. Yes, they want to make it easier for engineers to choose their parts, but in doing so they’ve done a lot of the work for you. Capitalizing on that work wherever possible only makes sense, and in this case the results were perfect for the task at hand.

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