A whole boss fight in 256 bytes

https://hellmood.111mb.de//A_whole_boss_fight_in_256_bytes.html

by HellMood • 4 months ago

130 52 4 months ago

hellmood.111mb.de

HellMood12• 4 months ago

Technical write up for "Endbot" 256 bytes MSDOS program with plot, sync, sound, and payoff. Released April 4th at Revision Demoparty 2026.

ale42• 4 months ago

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)

bitwize• 4 months ago

We're gonna find that Claude Mythos can do something like this in 255 bytes

HellMood12• 4 months ago

I mean now that the (human written) source for this is out in the wild, of course it can ;)

streetfighter64• 4 months ago

Optimizing away one byte of this, given the source code? Yeah, could happen. Making a good 256 byte demo from scratch? No way.

HellMood12• 4 months ago

I ran a patched version of it on WinXP (DOS NTVDM), the sound works there! But it requires a few extra bytes to enable MIDI UART Mode first. On DosBox-X, this can simply be set in the config ;)

lucb1e• 4 months ago

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".)

flopsamjetsam• 4 months ago

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.

rustystump• 4 months ago

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.

senfiaj4• 4 months ago

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.

layer8• 4 months ago

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.

irishcoffee• 4 months ago

It is misleading to say "I wrote X in 1k bytes" when those 1k bytes were library calls to library calls totaling 300MB.

xg15• 4 months ago

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".

gmueckl• 4 months ago

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.

ErroneousBosh• 4 months ago

But there's nothing stopping you running it on a real DOS machine.

I expect someone will then say "though in practice today it's 256 bytes of binary plus a whopping 64kB of BIOS ROM and 16kB of video RAM" ;-)

rwoerz• 4 months ago

Or a 256 bytes prompt

TeMPOraL• 4 months ago

That actually deserves a competition of its own. Just what can you accomplish with a 256 bytes prompt? Or maybe 32 bytes, to compensate for expressiveness of natural language.

TapamN• 4 months ago

Well, it's "256 bytes of x86" (plus X KB of VESA bios) (plus Y KB of FM synth patches) (plus Z KB of microcode) (plus...)

philxor• 4 months ago

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

omoikane• 4 months ago

Writeup:

https://www.reddit.com/r/tinycode/comments/1se0iyt/writeup_f...

HellMood12• 4 months ago

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

tromp• 4 months ago

You can do amazing things in 8 bytes [1].

[1] https://tromp.github.io/blog/2026/01/28/largest-number-revis...

parkertomatoes• 4 months ago

Audio doesn't work, but here's an emulator link

https://parkertomatoes.github.io/v86/?type=com&content=aACgB...

HellMood12• 4 months ago

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

s3anw3• 4 months ago

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.

vermilingua• 4 months ago

Another incredible 256b demo: https://linusakesson.net/scene/a-mind-is-born/

HellMood12• 4 months ago

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 =)

senfiaj4• 4 months ago

This one as well https://frankforce.com/city-in-a-bottle-a-256-byte-raycastin...

HellMood12• 4 months ago

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

rob744• 4 months ago

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".

HellMood12• 4 months ago

it's fine, you're right ;)

i'm thinking of making that interactive, remove (a bit of) sound and plot timing (which takes surprisingly many bytes!)

but i won't spoil anything until it's ready ;)

JoshBlythe• 4 months ago

What a throwback! Reminds me of older gameboy games! Really nice project!

gavinray• 4 months ago

My favorite SNES game (Uncharted Waters 2) is a 2MB ROM.

I think about that every time I send a screenshot. The depth, complexity, and audiovisual beauty of that game stuffed into a space roughly a few times larger than a capture of my 1440p monitor in 2026.

A whole boss fight in 256 bytes

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