Hate to be that guy, but I just can't help it: this is an impressive demo, but for me a "boss fight" is something interactive, which this program obviously isn't. That's probably the reason why the title of the article is (now?) simply "Endbot", while the name of the HTML file is (still?) "A_whole_boss_fight_in_256_bytes.html".
That domain is such a blast from the past for me. I spent so many hours working on projects with free webhosting as a teen!
dang/HN: this domain should probably be added to the list where the subdomain is shown next to the title, since subdomains are users' webspaces. (Might be a good candidate for the public suffix list: "[DNS labels] under which Internet users can (or historically could) directly register names".)
The demoscene has a curated collection of "best 16 bytes ever"
https://nanogems.demozoo.org/#16_byte_intros
As well as 32,64 and so on ...
It even goes down to 8(!) Byte productions
Unless I'm overlooking something, the demo only requires DOSBox to have a machine with predefined execution speed. There are no DOS interrupt calls that I can see. Other than that, the program could probably even be trivially modified to fit in a floppy disk MBR and could potentially run without underlying OS.
To be more exact (in an excessive way), it uses the BIOS's code to set the video mode (INT 10h) which is probably a few dozen bytes (at least?) although I have been remiss at not ever reading them. And it depends on DOS configuring the memory space to leave an INT 20h call (to terminate the program) at a place that's easy to RET to. But, yeah, very little extra. But I'm not being negative at all and this is pretty nice code and on the impressive side of 256 byte demos from the 80s and 90s (and onward).
Yes, this is very minimal; if it were self-booting the INT 20h call wouldn't be needed, but there's no getting around the INT 10h, unless you specialize for very specific hardware.
The entire 5150 BIOS fit in 8k, so even if it were laden with BIOS calls (which it's not) then that would be an upper-bound.
Why is that bad? If the bytes could easily run within the same constraint in another env/language why the hate?
I am with u on the excessive ram of browsers. It is insane. Still, it is one of the most portal and easy ways to share something. Heck, u can run a dos emulator in your browser.
This is probably in reference to things like Dwitter.net (https://news.ycombinator.com/item?id=46557489), where the browser (plus the Dwittet-specific runtime harness) contributes significantly higher-level functions than traditional demoscene targets like DOS PCs.
It’s just a different thing. I see no “hate”, only an expression of preference for “bare-metal” demos.
Probably because JS has larger runtime, in JS you don't have to write about most of the low level code. So it's easier to squeeze code in JS than in ASM or machine code.
This takes me back to the NES era, where developers squeezed entire worlds into a few kilobytes of ROM. What blows my mind here is that even the NES had ~40KB of program space — and this entire boss fight, complete with sprite animation, scrolling landscape, and MIDI music, fits in 256 bytes. The NES ROM header alone is 16 bytes. Incredible work.
For all lovers of 256Bb intros (and 128,64 and so on)
there is a curated "best of" selection maintained by
Demosceners : https://nanogems.demozoo.org/#256_byte_intros
"A mind is born" is of course included there =)
Didn't run it (yet) but it looks nice. Great that some people are still able to optimize code! I'm wondering if this would run on actual hardware (VGA + a sound card supporting MPU401 emulation)
Hate to be that guy, but I just can't help it: this is an impressive demo, but for me a "boss fight" is something interactive, which this program obviously isn't. That's probably the reason why the title of the article is (now?) simply "Endbot", while the name of the HTML file is (still?) "A_whole_boss_fight_in_256_bytes.html".
https://www.pouet.net/prod.php?which=105909
The "silent" version is only 219 bytes
A new version that adds new features into
the remaining bytes is in the works
That domain is such a blast from the past for me. I spent so many hours working on projects with free webhosting as a teen!
dang/HN: this domain should probably be added to the list where the subdomain is shown next to the title, since subdomains are users' webspaces. (Might be a good candidate for the public suffix list: "[DNS labels] under which Internet users can (or historically could) directly register names".)
And it came in 5th place in the competition. The winner was this one which is 16 bytes...
https://www.youtube.com/watch?v=QKLhH_ANwIc
The demoscene has a curated collection of "best 16 bytes ever" https://nanogems.demozoo.org/#16_byte_intros As well as 32,64 and so on ... It even goes down to 8(!) Byte productions
You can do amazing things in 8 bytes [1].
[1] https://tromp.github.io/blog/2026/01/28/largest-number-revis...
You can (on real MSDOS!) go as low as 6 bytes
https://www.pouet.net/prod.php?which=63538
But most people wouldn't find that visually satisfying
The technical details why this works are very interesting though :)
Writeup:
https://www.reddit.com/r/tinycode/comments/1se0iyt/writeup_f...
I clicked on this fearing it was a "256 bytes of JS" (plus X GB of browser), and was pleasantly surprised it was actually 256 bytes.
Had a similar thought. In theory, you're right, though in practice today it's "256 bytes of binary plus X MB of DOS emulator".
Unless I'm overlooking something, the demo only requires DOSBox to have a machine with predefined execution speed. There are no DOS interrupt calls that I can see. Other than that, the program could probably even be trivially modified to fit in a floppy disk MBR and could potentially run without underlying OS.
To be more exact (in an excessive way), it uses the BIOS's code to set the video mode (INT 10h) which is probably a few dozen bytes (at least?) although I have been remiss at not ever reading them. And it depends on DOS configuring the memory space to leave an INT 20h call (to terminate the program) at a place that's easy to RET to. But, yeah, very little extra. But I'm not being negative at all and this is pretty nice code and on the impressive side of 256 byte demos from the 80s and 90s (and onward).
The VBIOS is around 32-64k. The modesetting path is probably a few k.
And it depends on DOS configuring the memory space to leave an INT 20h call (to terminate the program) at a place that's easy to RET to.
This has always been the case, and actually inherited from CP/M.
Yes, this is very minimal; if it were self-booting the INT 20h call wouldn't be needed, but there's no getting around the INT 10h, unless you specialize for very specific hardware.
The entire 5150 BIOS fit in 8k, so even if it were laden with BIOS calls (which it's not) then that would be an upper-bound.
Or a 256 bytes prompt
Why is that bad? If the bytes could easily run within the same constraint in another env/language why the hate?
I am with u on the excessive ram of browsers. It is insane. Still, it is one of the most portal and easy ways to share something. Heck, u can run a dos emulator in your browser.
This is probably in reference to things like Dwitter.net (https://news.ycombinator.com/item?id=46557489), where the browser (plus the Dwittet-specific runtime harness) contributes significantly higher-level functions than traditional demoscene targets like DOS PCs.
It’s just a different thing. I see no “hate”, only an expression of preference for “bare-metal” demos.
Here's a 13-byte demo that runs on Chrome browsers:
It is misleading to say "I wrote X in 1k bytes" when those 1k bytes were library calls to library calls totaling 300MB.
Right... on the flipside its one thing to where it is X+minor overhead inclined lib calls
Then a whole nother level of awesome where its literally just ASM
Probably because JS has larger runtime, in JS you don't have to write about most of the low level code. So it's easier to squeeze code in JS than in ASM or machine code.
Technical write up for "Endbot" 256 bytes MSDOS program with plot, sync, sound, and payoff. Released April 4th at Revision Demoparty 2026.
This takes me back to the NES era, where developers squeezed entire worlds into a few kilobytes of ROM. What blows my mind here is that even the NES had ~40KB of program space — and this entire boss fight, complete with sprite animation, scrolling landscape, and MIDI music, fits in 256 bytes. The NES ROM header alone is 16 bytes. Incredible work.
Audio doesn't work, but here's an emulator link
https://parkertomatoes.github.io/v86/?type=com&content=aACgB...
The sound works in DosBox-X if you use the providesd config file
It also works on real old DOS PCs (or Windows XP/98 "DOS") but it would require changing a few bytes, mainly to setup UART MIDI mode
Another incredible 256b demo: https://linusakesson.net/scene/a-mind-is-born/
Absolutely!
For all lovers of 256Bb intros (and 128,64 and so on) there is a curated "best of" selection maintained by Demosceners : https://nanogems.demozoo.org/#256_byte_intros "A mind is born" is of course included there =)
Didn't run it (yet) but it looks nice. Great that some people are still able to optimize code! I'm wondering if this would run on actual hardware (VGA + a sound card supporting MPU401 emulation)
We're gonna find that Claude Mythos can do something like this in 255 bytes
Optimizing away one byte of this, given the source code? Yeah, could happen. Making a good 256 byte demo from scratch? No way.
I mean, give it a try?
the source is right there ;)
I mean now that the (human written) source for this is out in the wild, of course it can ;)