Show HN: I recreated 90s Mode X demoscene effects in JavaScript and Canvas

https://jdfio.com/pages-output/demos/x-mode/

189•gneissguise•7mo ago

After 25 years of writing software, I was feeling nostalgic for the kinds of things that got me into programming in the first place: the old DOS demoscene. I spent a weekend seeing if I could recapture some of that INT 13H VGA magic using today's web tech, but with the old-school constraints of doing it from scratch.

The result is this portfolio of ten classic effects running in a single HTML file. It's all vanilla JavaScript writing to a <canvas> element, with no external libraries. It was a fun challenge to implement things like:

* The color palette cycling and smooth fading in the Plasma demo. * The buffer-averaging algorithm for the Fire effect to make the flames feel more natural. * The distance-based texture crossfading in the Tunnel to create the illusion of flying through different sections. * A 2D scalar field for the Metaballs to calculate the surface normals for that classic blended, metallic look (I did the best I could with the given constraints).

It was a great exercise in getting back to first principles and a reminder of how much those early demo programmers could accomplish with so little. I hope it brings back some good memories for others who grew up with this stuff.

I'd love to hear about your favorite classic demos or if there are any other iconic effects you think would be a fun challenge to add.

Cheers!

Comments

pentaphobe•7mo ago

Neat! The nostalgia is palpable.

Off topic: we always referred to mode-x variants as MCGA, TIL that's more of a colloquial term than a technically accurate one [1]

[1]: https://en.m.wikipedia.org/wiki/Multi-Color_Graphics_Array

gneissguise•7mo ago

Thanks for sharing, I do not believe that I was familiar with that term at the time.

snozolli•7mo ago

AFAIK, MCGA has nothing to do with Mode-X. Mode-X was 320x240, and was achieved by manipulating VGA settings. MCGA supported Mode 13h, but I see no evidence that it could be manipulated to output 320x240 or that it supported planar memory, which is generally considered synonymous with Mode-X. In fact, from what I can tell, MCGA didn't have enough memory to support planar mode.

guiambros•7mo ago

wow, well done! Pretty solid implementation, genuinely Future Crew-worthy :)

gneissguise•7mo ago

w00t! Greetz!!!1

pengaru•7mo ago

Neat, but beyond the 320x240 resolution I don't have the impression you're really emulating anything uniquely mode-X here (not that it would really make sense to do so)

gneissguise•7mo ago

You would be correct, it's more the appearance of the demoscene than the actual underlying mechanism.

A true in browser mode-x API would take me much longer than a weekend to implement.. But it does sound like a neat challenge!

juhanakristian•7mo ago

Well done! These look very authentic. I remember creating the fire and plasma effects when I was first learning how to code in the late 90s.

gneissguise•7mo ago

Oh yes, I have similar memories mixing asm and pascal together in Turbo Pascal to get interesting results!!

KingOfCoders•7mo ago

More like 80s Amiga effects :-)

gneissguise•7mo ago

I could see that too.

I didn't own an Amiga but a friend of mine from school did. We had a blast playing Gobliiins!

KingOfCoders•7mo ago

I think starfield was the first effect I wrote as a demo coder in the 80s. Then a Copper wobbling picture I think (Like the Star frontier intro) - or copper bars, then a sin scroller. Nearly joined TRSA because one coder in our group was a genius (not me!) but deal fell through :-(

gneissguise•7mo ago

Oh man that would have been so cool! Sorry that it fell through..

I remember making infinite ASCII mazes by alternating forward and backward slashes in the late 80s early 90s. That would have been the grade school computer lab days for me and I didn't have the to do anything better so it was mazes or controlling the turtle in LOGO

KingOfCoders•7mo ago

https://10print.org/ <3

gneissguise•7mo ago

Wow now that brings back memories! Thanks for the link!

dr_dshiv•7mo ago

Thanks for putting this together!

I’ve been thinking a lot about demoscene in a Vibecoding era. Demoscene was often very close to the metal; Vibecoding is often completely abstracted from it.

To explore this tension, I’m cohosting an 8bit game design workshop (pico8) in Amsterdam this summer. Just for fun.

Working with intense constraints can bring a lot of creativity. I really want to see how AI affects the workshop vibe.

gneissguise•7mo ago

It was my pleasure to work on and share, glad you liked it!

elpocko•7mo ago

>very close to the metal

>(pico8)

But PICO-8 with its integrated tools and Lua programming is super high level, pretty far removed from "8bit". It's only 8 bit in aesthetics, entirely artificial and forced. Why not write games for the 2600, the C64 or the NES to experience real constraints of an actual 8 bit platform, the actual "metal."

dr_dshiv•7mo ago

I know, tell me about it, we’ve been debating this, tbh. We landed on pico8 to introduce the ideas of creativity within constraints as there is a very active community and nice tooling. We’ve done NES workshops before, but always with CS students and eproms. 6502 assembly isn’t that complicated, but can be scary.

elpocko•7mo ago

I've been thinking about making a fantasy computer/console that uses an emulated 65C02 CPU, maybe a bit simplified -- every instruction only taking 1 cycle, for example. You could use all existing tools for the 6502, like the amazing 64tass, and there's an interesting high level language called prog8 (https://github.com/irmen/prog8) that's relatively easy to use. Not sure if there's any interest for something like that.

Lerc•7mo ago

I was working on something using AVR assembly as a fantasy console.

I never quite completed it, but I managed a emulator/assembler IDE in the browser. Making my own assembler let me play around with some ideas for macros.

It could even load programs from gists.

https://k8.fingswotidun.com/static/ide/?gist=ad96329670965dc...

Reflecting on it now, I think one feature that could help a assembler on devices like this is the ability to inline compile assignment expressions that use values of only one type. It would be easy enough to emit a stream of instructions for

    x=32+(x*(y+2))

or even

    r15=32+(r15*(y+2))

using registers as expression values.

The result would usually be what an assembler writer would write themselves.

I think a macro assembler that did that would ease a lot of the tedium of assembly while maintaining the near absolute control over memory use and IO that you need for low level coding.

ceronman•7mo ago

Hi! That sounds very interesting, where can I find information about this workshop? I am interested in participating.

dr_dshiv•7mo ago

thanks! my contact info is in my bio. Drop me a line -- the website might be up later today... or next week haha. But several friends flying into Amsterdam to make this a reality.

imiric•7mo ago

Vibecoding is entirely antithetical to demos.

Demos aren't just pretty visuals. Their entire purpose is to showcase the skills of the programmer in accomplishing something remarkable within a constrained environment, or within artificially imposed constraints. Using exorbitant amounts of resources to run a machine learning model to generate a muddy mixture of existing demos goes completely against this spirit. The idea of the two together is, frankly, repulsive.

dr_dshiv•7mo ago

Be repulsed then! We are doing the workshop specifically to explore this tension. I’m well aware that times are weird.

This workshop is actually a forerunner to a workshop on demos with quantum computers, where the constraints are very real and creative participation is very lacking.

esafak•7mo ago

The game is to see who can prompt the LLM spit out the tightest code!! Sergey Brin says threatening the LLM works in a pinch!

kookamamie•7mo ago

Nice. Except that Mode X was not usually called 13h. The former would be 320x240 and the latter 320x200. Technically X would be a variant of the 13h, though.

ale42•7mo ago

And actually, INT 13h is the BIOS interrupt to access block-based disk I/O functions (like sector read, track format, etc.). The INT used for mode-setting is 10h (with AH=00h and AL=13h as mode for 320x200 at 256 colors).

gneissguise•7mo ago

Thank you both for the corrections, I was a teen in the 90s so I could have had it wrong or misremembered.

I just looked up the 13h interrupt and you are absolutely right!

kookamamie•7mo ago

An awesome contribution nevertheless!

gneissguise•7mo ago

Thank you!

QuiCasseRien•7mo ago

thank for make me back to 25 years ago with the star windows screensaver ^^

gneissguise•7mo ago

Anytime! I was also trying to add a Star Wars like hyperspace feature to the starfield demo but I failed miserably at implementing it!

abrookewood•7mo ago

Thank you - takes me back :)

gneissguise•7mo ago

You're welcome, it's my pleasure to share with ya!

luismedel•7mo ago

Nice. But if I remember correctly, Mode X was a special VGA mode to squeeze a bit more performance (due to planes and full graphics memory addressing), not the "normal" MCGA 320x200x256 (13h)

If you're interested, I also implemented a few effects like lens[0] and Jare's fire[1] along with some other amusements[2]

[0] https://toys.luismedel.com/lens/index.html

[1] https://toys.luismedel.com/fire/index.html

[2] https://github.com/luismedel/js-toys

gneissguise•7mo ago

Thanks for sharing the link! I remember the lense demos, and I remember downloading one or two of them from a BBS that had NSFW pictures rendered in the background.

wvh•7mo ago

That's one way to stimulate memory...

I was so into this in the mid-90s. I tried some assembly but I wish I would have been better at the maths part back then.

bhouston•7mo ago

X-Mode is formally:

320x240 (square pixels) with 256 colours

Full details:

https://en.wikipedia.org/wiki/Mode_X

rareitem•7mo ago

Amazing, I was not born in that era but it makes me feel nostalgic too. How does on go on to learn to make animations like this?

gneissguise•7mo ago

Start off small, you gotta know your underlying API. For this demo it's JavaScript and the HTML5 canvas API (which is MUCH easier to learn than the languages of the 90s except for BASIC)

https://www.freecodecamp.org/news/drawing-on-a-canvas-elemen...

From there, you'll need a good understanding of loops, control flow, data structures like arrays to store the pixels, lines, shapes, and colors, wiping and redrawing the screen between "ticks" (a single pass of the main loop), and refresh timing to control the speed of the animations.

On a side note there's actually a refresh bug in my plasma demo I just noticed a moment ago... if you leave it open for too long on plasma it starts redrawing faster and faster until it looks like glitch-art!

rollulus•7mo ago

Good job. Looks authentic. But you forgot the rotozoom!

gneissguise•7mo ago

D'oh! Now that I'm in my mid 40s there's so much I've forgotten!

Thank you for the reminder

leptons•7mo ago

You should check out dwitter.net if you have not already.

gneissguise•7mo ago

Just took a look, very cool algorithmic art! Thanks for sharing!

stuaxo•7mo ago

Wonderful. Did you simulate through weird bitplains of VGA?

I found them hard to get my head round, still do.

gneissguise•7mo ago

Excellent question. This is more a modern chunky pixel framebuffer, not planar.

The spirit of the project, however, was to emulate the tricks that bitplanes made famous. The plasma and flag effects, for example, don't move any pixels; they just cycle the color palette's offset against a static pattern, which is a direct software simulation of that classic Amiga hardware hack.

TrackerFF•7mo ago

The vector one is still alive and kicking. I've lost count how many current websites have that one on their landing page.

gneissguise•7mo ago

Yep it has totally made a resurgence with the background animation trend showing up in modern web UI.. except without the pixelated appearance and the green phosphor color.

p1dda•7mo ago

Thanks! So great to watch these demos in 80-90's of the wizards creating these spectacular visuals.

gneissguise•7mo ago

Heck yeah you're welcome! It was a blast to put together

gneissguise•7mo ago

If anyone is interested in doing algorithmic art while learning Clojure/ClojureScript then I highly recommend checking out the Quil library:

https://landofquil.clojureverse.org/

http://quil.info/

https://github.com/quil/quil

Just lean into the declarative lisp style and immutable data and make some beautiful art to share with others!

stuaxo•7mo ago

Would like to see an old school vowel landscape.

TuringNYC•7mo ago

Great nostalgia! You should also do the multi-colored rolling pipes, that was a staple!

layer8•7mo ago

Already in the 80s, though.

bhouston•7mo ago

good job!

gneissguise•7mo ago

Thank you very much!

I love how I never get any accolades for my other engineering work, but this demoscene recreation was a smash hit! Not complaining at all, I'll take any recognition I can get.

I've been recovering from major burnout earlier this year, and this has lifted my spirits exponentially.

I appreciate your comment and all the kind words others have shared.

bhouston•7mo ago

BTW I myself was a demo scene coder back in high school, which for me was 1995-7:

https://github.com/bhouston/2DBumpMapDemo1996

https://github.com/bhouston/3DMaskDemo1997

gneissguise•7mo ago

Nice bumpmapping and phong shading!

lofaszvanitt•7mo ago

Second Reality waaa

layer8•7mo ago

Has anyone ported it to JS yet?

gneissguise•7mo ago

Not sure, but Future Crew was soooo good. Someone should take a stab at it!

I can offer what little I know to help.

ryan42•7mo ago

I always liked this one. it is really impressive and I used it as a screensaver for many years.

https://www.pouet.net/prod.php?which=53816

gneissguise•7mo ago

Indeed, that is very impressive!!!

doublerabbit•7mo ago

https://www.wab.com is another beautiful resource for demo enthusiasts. JS too.

gneissguise•7mo ago

Whoa cool, thank you for sharing that link!

rep_movsd•7mo ago

May I humbly request you to join the dwitter.net community?

gneissguise•7mo ago

You're the second person to mention dwitter.net, now I feel like I have to... Got a busy week coming up but when I have more downtime I'll join and share!

tmaly•7mo ago

this reminds me of choosing a screen saver for my CRT monitor in the early days.

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Comments