Empire of the Absurd: A Brief History of the Absurdities of the Soviet Union (laurivahtre.ee)

For HTML Day 2025 [1], I made a web service that displays the current sky at your approximate location as a CSS gradient. Colours are simulated on-demand using atmospheric absorption and scattering coefficients. Updates every minute, without the use of client-side JavaScript.

Source code and additional information is available on GitHub: https://github.com/dnlzro/horizon

[1] https://html.energy/html-day/2025/index.html

Comments (29)

ryandrake · 1h ago

Awesome. I remember much earlier in my career I was working on a 3D turn-by-turn navigation software, and one of my tasks was to draw the sky in the background. The more senior guy on the team said, just draw a blue rectangle during the day and a dark gray one at night and call it job done. Of course, I had to do it the hard way, so I looked up the relevant literature on sky rendering based on the environment, latitude, longitude, time of day and so on, which at the time was Preetham[1] ("A Practical Analytic Model for Daylight"), and built a fully realistic sky model for the software. I even added prominent stars based on a hard-coded ephemeris table. It was quite fast, too.

Well, the higher ups of course hated it, they were confused as to why the horizon would get hazy, yellowish, and so on. "Our competitors' skies are blue!" They didn't like "Use your eyes and look outside" as an answer.

Eventually, I was told to scrap it and just draw a blue rectangle :(

All that to say, nice job on the site!

1: https://courses.cs.duke.edu/cps124/fall01/resources/p91-pree...

zarzavat · 5m ago

You should have added a duck.

darknavi · 42m ago

A past coworker who worked on Cobalt[1] told me that they spent entirely too much time implementing stars in the sky of the game with some amount of real(ish) star system physics behind them.

I can understand people removing polish things like that if there are usability concerns, but those small things add up to a lot in an end product and are a joy to find and explore.

1: https://en.wikipedia.org/wiki/Cobalt_(video_game)

netsharc · 1h ago

Not even as an easter egg?

You could've sold it with telling them Vincent Van Gogh's paintings had the location of stars accurately, you were inspired by those paintings to reproduce the sky color accurately.

j_bum · 1h ago

Fun (but not fun) story :)

throwanem · 1h ago

> the little-known meta http-equiv="Refresh" HTML tag

Oh, don't mind me, I'll just be over here in the corner laughing ruefully as my bones crumble to dust: back when I started, if you wanted a page to refresh on its own, this was the only way.

Beautiful work! A splendid example of formal minimalism at its best.

dlazaro · 1h ago

Thank you! And umm, not to make you feel ancient, but I think I wasn't even alive yet when `setTimeout(() => location.reload(), ...)` first became widely available.

nhinck3 · 1h ago

Opened this up and sat there for a good 20 seconds waiting for something to happen... only to remember it's midnight here.

dlazaro · 43m ago

Maybe someone smarter than me could add stars to the night sky, so it's not just black.

esafak · 37m ago

More sophisticated than I expected. It relies on a research paper: https://github.com/ebruneton/precomputed_atmospheric_scatter...

101008 · 26m ago

Put my phone against the window and I had to call over my wife to come to check it: it matches 100% (clear sky right now). It's amazing, congratulations

nisten · 1h ago

i put my laptop next to the window and it was spot on wtf

what got me the most is opening chrome dev tools and seeing nothing there

xattt · 25m ago

This would be an awesome background for a smart home dash!

gdubs · 41m ago

Well, that's delightful. Works really well here in the Pacific Northwest :)

djoldman · 1h ago

@dlazaro, I believe that style={{backgroundColor: bottom}} is not needed in:

    <body style={{backgroundColor: bottom}}> </body>

is not needed.

dlazaro · 50m ago

I actually included that so the tab and status bars are themed on iOS/Safari. Here's someone else's writeup on that: https://medium.com/@evkirkiles/coloring-the-webkit-browser-b...

peterldowns · 42m ago

That's a cool thing to know, thanks for sharing. Great job on the sky site!

ianbicking · 1h ago

I'm around so much wildfire smoke lately that my sky expectations have changed...

I wonder what it would take to account for weather?

craftkiller · 59m ago

That'd be a pretty large introduction of a dependency. The sky can be calculated with just lat/lon and the current date+time. Adding in weather would mean querying some external weather service.

i_love_retros · 1h ago

Curious why a celebration of HTML needed a full stack javascript framework?

dlazaro · 46m ago

A server is needed to calculate the sun's position from latitude + longitude + time, and then render the gradient. I could use HTML templating in some other language/framework, but I used Astro because that's what I'm familiar with and it's very easy to deploy to Cloudflare Pages.

stephenlf · 2h ago

Fantastic. I’ve always wondered why the sky wasn’t blue around the horizon. Fascinating stuff.

verandaguy · 1h ago

There's two main reasons for this:

- First and most impactful: as the earth curves down and away from the observer's horizon, your line of sight goes through a thicker slice of the atmosphere.

Looking straight up you might have 100km of atmosphere until space (the distance is made up here, but I'm using the Kármán line as an arbitrary ruler), but looking out towards the horizon (assuming a perfectly spherical Earth), it's much, much more than that 100km, so the light will scatter off of (and/or be filtered by, depending on angle and time of day) more particles in the atmosphere, affecting the colour of the sky.

- The compounding factor here is if there are environmental factors that boost the particle count in the air, and especially particles that'd stay in lower layers of the atmosphere. Where I am, we've been dealing with wildfire smoke of varying strengths for a few weeks. Today's gentle enough, but it's bad enough that my gradient goes from rgb(115, 160, 207) at the top of the sky to rgb(227, 230, 227) at the horizon (which is shockingly accurate).

mlhpdx · 1h ago

Which direction am I looking? Deeper blue to the north.

dlazaro · 42m ago

It's always facing the sun (although it doesn't include the sun itself).

nnnnico · 1h ago

incredible <3 not much else to say

jhardy54 · 46m ago

Super neat. Looking forward to checking out your implementation and learning about this!

hoppp · 1h ago

Seems to work :)

siva7 · 1h ago

how i missed this small hn posts. thanks