dlazaro5d

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

159 comments
  • ryandrake5d

    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...

    • crazygringo5d

      This is why specifications are important, and why design is important.

      The reality is that we have certain conventions that are immediately understandable, and that too much visual complexity results in confusion rather than clarity.

      If the sky is hazy white when I expect it to be blue, I'm confused as to whether it's the sky or if the map is still loading. It's adding cognitive complexity for no reason. Stars similarly serve no functional purpose at night.

      What you built sounds great for an actual planetary view like Google Earth. And it sounds fun to build. But it's an anti-feature for a navigation view. When you're navigating, simplicity and clarity are paramount. Not realism.

      • dylan6045d

        > This is why specifications are important, and why design is important.

        Also the phrase "know your audience". No sense in casting pearls before the swine.

        • resonious5d

          Though sometimes the higher ups might not be the same as (or understand) the actual audience.

          In this case the higher ups may have been confused due to, say, looking at the app while indoors (and from the perspective of "let's judge this developer's work"), while the actual users would see it in a vehicle alongside the real sky (and from the perspective of "let's see how easy this is to match up with reality").

          • dylan6045d

            Ah, I see the confusion. You think the users are the dev's audience! /s

            • resonious5d

              I suppose this is the lesson OP learned!

              • edoceo5d

                I wish more people knew it. So many times frustration of the system is directed at devs. They couldn't figure out X? Why is Z feature so shit? Etc.

                That's a management thumbprint on the deliverable.

      • wkjagt4d

        Also, any fanciness you add in your product is something you need to then maintain. Even after the developer that built it leaves the company.

        • carlosjobim4d

          It takes thousands of years for the stars to have changed positions in a noticeable way, and my best guess is that the customers will not use their car GPS for so long that this will bother them.

          • crazygringo4d

            Very funny, but in case you're serious, it's not the stars changing...

            ...it's the software frameworks. A new screen size. A different color depth. A bug when the graphics library is upgraded for antialiasing. Etc.

            • carlosjobim4d

              That's not going to be an issue with devices already sold. And if developers of future devices can't handle it they should probably be fired from their job.

              • crazygringo4d

                It's not a question of whether future developers can "handle" it. It's a question of whether the additional time required to maintain it is worth the cost. Maintenance isn't free. It takes time, and every little bit adds up.

                Also, devices already sold often get updates, so it's not even just about future devices.

      • johnfn5d

        Oh come now. You are being no fun.

    • darknavi5d

      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)

    • jbverschoor5d

      Whipping down the innovator with the stupidity whip. Great management

      • woah5d

        It sounds like the developer spent a lot of time implementing something that nobody wanted. Drawing the sky accurately may be cool, but it wasn't required in this case. It's also not innovation. It's been done before.

        This is like if you were renovating your house and the drywall guy spends a huge amount of time building up round corners, but you just wanted regular square corners. Then on some drywall forum they're bitching about how "all clients are stupid" or something.

        • alwa4d

          And, from the sound of it, the developer confused truth with beauty. Sometimes we’d prefer to see the sky the way we wish it were rather than the way it is.

          That’s an aesthetic call, not a “who can do the math” call.

          “Good news, I accurately simulated the particulate load in the local atmosphere—so now you authentically can’t read the text on a given smoggy winter morning!”

          (FWIW, grace for management decisions notwithstanding, I think what gp did is awesome, and would switch on full realism mode every time :)

      • idiotsecant5d

        This is a wildly unprofessional attitude. Programmers are craft(wo)men. They employ their craft toward creating things people pay them to create.

        We aren't painting sistine chapels, we are running the plumbing in the sistine chapels basement. The job doesn't exist to give you emotional fulfillment. A mason doesn't insist that a client who needs a warehouse must pay him to spend a week detailing corbelled brick cornices. He makes a CMU wall, in the cheapest and most efficient way that still gets the job done.

        It's profoundly disrespectful when we build monuments to our own ego instead of just getting the work done and it speaks to a professional immaturity of the highest order. That was one of the hardest lessons I learned as a fresh engineer and I see so often others that are just learning it. Sometimes people never learn it.

        • sgarland5d

          > We aren't painting sistine chapels, we are running the plumbing in the sistine chapels basement.

          Sure, but in plumbing - or any trade - there is a huge spectrum of quality of work. Tons of little details add up that confer the person’s skill level to anyone checking it out in the future.

          > It's profoundly disrespectful when we build monuments to our own ego instead of just getting the work done and it speaks to a professional immaturity of the highest order.

          When I insist that something must be done a certain way, it’s not for my ego, it’s because I know that a year from now, I will be called upon to fix it during an incident if I don’t do it right this time. I am so absolutely sick of hacky bandaids being thrown on the ever-increasing pile of tech debt. To me, it’s profoundly disrespectful when product tells engineering that yet again, they will not yield time to fix the backlog, and to ship New Feature X.

      • ChrisMarshallNY5d

        I've been in the developer's shoes. I've also been in the manager's shoes.

        It's not that simple. There's possibly better ways to deal with it, but for safety-critical stuff (like a navigation display in a vehicle), simple is much, much better. In many cases, there's actually laws and liability stuff involved.

        I once spent six months, developing an "un-asked-for" WiFi control app for a digital camera, and had it nuked. It worked much better than the shipping app (which was enjoying a richly-deserved one-star rating in the app store).

        The considerations had a lot to do with the corporate Process (note the capital "P"), which I sidelined. I thought I could do better, but the people with the hands on the brake, thought different. I didn't kiss the right rings. That's a very real consideration in any corporation.

        As a manager, however, I did go to bat for employees that displayed initiative. In some cases, I was successful. In some cases, not so much.

        • hobs5d

          There's so much decision making in companies that comes down to some dingus in management decided that it would Be Bad On Purpose. Fighting that battle is something you can try a few times in your career if you want, but it usually leads to burnout or a resume generating event.

      • ryandrake5d

        A foundational, core theme about making commercial software, that repeats over and over and I slowly got accustomed to is: companies really don't want these kinds of micro-innovations. 90% of companies are just looking at their competitors, making a checklist out of those products, and asking engineers to check the boxes and go home. They don't care about little details, about craftsmanship and polish, about lint warnings, about "oh, that's a nice touch," or even quality beyond "will the customer return the product?" They just want people to poop out software as fast as possible so everyone can get bonuses and drive around on their jetskis on Saturday.

        If you're the kind of developer who likes to "sand and finish the back side of the cabinet," either you need to find a very rare, special company, or do it at home as a hobby.

        • jbverschoor5d

          But it's exactly the thing that makes software "delightful". It's also a huge boost to the developer's appreciation, motivation, productivity, care for the product.

          But yeah, if you only care about checking the feature boxes.. Go ahead, make shit software with miserable people, but be sure to prepare to go out of business.

          • philipallstar5d

            The point is a real skybox is not great for satnav software. It's probably actually worse than a stylised mode, with a predictable colour background for anything that's going to sit on top of it.

            • jbverschoor4d

              That's exactly not the point. Where do you think innovation comes from?

              It comes from tinkering.

              • philipallstar3d

                It comes from all sorts of different things. Massive capital investment into R&D processes also. Depends on the thing.

        • cyberax5d

          > They don't care about little details, about craftsmanship and polish, about lint warnings, about "oh, that's a nice touch," or even quality beyond "will the customer return the product?"

          I worked at large companies, and there are reasons beyond that. I've been on the both sides of this fence.

          Senior engineers feel the pain of supporting all these features. You created a new streaming API prototype that provides a gradual response, progressively displaying details of the 3D model? Great. But it's 15000 lines of dense code without a lot of explanation. Who is going to support it once you leave the company? Is it secure? How does it work with kiosk-type browsers? Can you write a formal proposal so we can start the review process?

          Oh, I see that you're already leaving the company :(

          And that's also why startups are often so much more successful initially. They just don't care about the long-term support and YOLO a lot of functionality.

          • jbverschoor4d

            Sure.. but all there prototypes don't have to be released. It's part of innovation. And maybe you'll even find a new product or a competitive edge.

    • zarzavat5d

      You should have added a duck.

      • otikik5d

        I understood that reference

    • netsharc5d

      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.

    • benrutter5d

      Ironically, I'm in the South of England wih clear blue sky, and the site thinks I have a much darker and beautiful reddish sunset. Im fairness, it's probably only out by an hour if that.

    • bravesoul25d

      The thing here is programming the job can be much more dull than programming the hobby. Occasionally (twice a decade) there can be a collision where you get to do something really cool like that at work. The higher ups want a realistic sky because their market research said it'll boost an OKR by 10 basis points. And then you are in luck!

      That said there are niches where jobs let you do cool stuff all the time. Hard to find. Probably why gaming jobs are notoriously underpaid and overworked.

    • Waterluvian5d

      I’ve had similar issues at work where people really overdo something and it’s difficult. On one hand you never want to kill that joy and passion someone has. That’s a great characteristic. But projects have scopes and too often instructions like “just draw a blue rectangle” get ignored.

      • ryandrake5d

        Totally. It was a harsh but needed lesson on the realities of getting work done in a commercial environment.

    • marcosdumay5d

      Yep, if you have to draw the Sun, you better draw it yellow. If you have to draw a cloudless day sky, you better draw it blue.

      That doesn't apply to every single instance of those, but if the sky isn't the focus of your application, a realistic one is just a distraction.

      • dylan6045d

        > Yep, if you have to draw the Sun, you better draw it yellow.

        This one always gets me in how dirty the sky must have been "back in the day" in order for people to see a yellow sun. I've never looked into what gas would be needed to make the sun look yellow, but it must have been hell to breathe.

        • card_zero4d

          Nah, the ancient Egyptians, and other cultures, depicted the sun a lot, and never made it white. Red, quite often, gold, very frequently - warm colors. If you paint a white sun people say it's the moon.

        • withinboredom5d

          The walls were black for a reason in big cities. All those chimneys and coal everywhere.

    • nkrisc4d

      That sounds really cool but I have to reluctantly agree with the senior: a cartoonish day/night sky is better than a half-implemented realistic one. I say “half-implemented” because it sounds as though yours didn’t account for local weather and cloud cover, which is reasonable but then incomplete. Even if you did, well, it’s turn-by-turn navigation. I expect the sky color to be selected for ideal contrast with the important UI elements to reduce the time spent looking at it while driving.

    • teaearlgraycold5d

      To be honest I don’t think anyone wants that kind of functionality - maybe in the satellite view but not in the vector map.

    • j_bum5d

      Fun (but not fun) story :)

    • maddmann4d

      Haha it sounds you applied the opposite of the YAGNI principle building this.

    • GuardianCaveman4d

      I identify so much with your sentiment and this type of overthinking overbuilding .

  • throwanem5d

    > 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.

    • mintplant5d

      Of course, the "http-equiv" means that this tag is supposed to stand in for an equivalent HTTP header, so you could accomplish the same by sending a "Refresh: 60" header :)

      • throwanem5d

        Sure, if you wanted to deal with configuring Apache. Or getting your hosting provider to do that. If you knew to ask, and didn't mind waiting, and your hosting provider knew how...

        • dudus5d

          Not sure what you are on about. Adding an HTTP header to a request is one of the easiest things to do.

          • urquhartfe5d

            I think you are the one who doesn't know what they are on about.

            First, the header must be added to the response, not the request.

            Second, in many environments (managed hosting etc.) there is not an easy way (or indeed a way at all) of adding headers to responses.

            • KTibow5d

              > Second, in many environments (managed hosting etc.) there is not an easy way (or indeed a way at all) of adding headers to responses.

              It's getting better. Most serverless hosts (including Cloudflare, which this site uses) follow the (req: Request) => Response pattern, which by definition allows sending headers.

            • bapak5d

              What are you talking about. Any non-static hosting will let you specify headers with a plain php function. Any baseline shared hosting offers that kind of control and has done so for the past 20+ years.

            • dylan6045d

              is that something that could have be done in the dot file for server override? what was it, .htaccess or something?

              • throwanem5d

                Sure, if you wanted to deal with configuring Apache. Or getting your hosting provider to do that. If you knew to ask, and didn't mind waiting, and your hosting provider knew how...and was willing to do it, a condition I forgot to add in my last comment here, but which applies equally there. (User-provided .htaccess files were the source of a number of relatively high-profile early CVEs, as I recall. Apache grew a number of options for trusting their content, and I want to say before very long you could not rely on anything working past simple HTTP-Basic credential management.)

                Oldschool shared web hosting was a shockingly deprived environment by modern standards, which is why my Linode account turned old enough a few months ago to buy a drink in a bar: $20 a month in 2004 was amply worth gaining a degree of control over web server configuration which is broadly the default assumption now.

                Since I was also administering some shared web hosting in my own right at the time - partially overlapping with my web design work targeting shared hosting, since some customers preferred to BYO - I don't blame admins for being difficult to work with; we all had good reason to be, with the afterthought security typically was everywhere in those days. But you begin perhaps to see why bypassing the whole rigamarole with a hint to the client was attractive.

                • dylan6045d

                  but that was the point of the dot file to allow vhosts to change the default server settings without needing access to the root config. maybe they weren't designed specifically for vhosts, but that was my main use of them.

                  • throwanem5d

                    Yes. If the main Apache config was set up to allow it to read a dotfile, and if configured not to ignore the options you wanted to use, that is what the dotfile did. That's why, if you wanted an option easily portable across hosting providers, you used the meta tag instead. Which is my point, and my only point, and not really up for debate by some pettifogging rando with nothing better to fill a Saturday night.

                    • dylan6045d

                      Wtf, seriously. I was just asking. Sorry if that resulted in me pissing in your cheerios. Just because a question was asked doesn’t mean it was challenging your knowledge. I was just asking to clarify based on personal experience. If you don’t have time for questions or feel personally slighted that someone would have the gall to question the written word of the almighty throwanem, then posting on the internet is probably something you stop doing

                      • throwanem5d

                        It isn't a question of "challenging [my] knowledge," it's a question of you acting like kind of a jerk. I realize you don't see yourself as the one starting an argument here, and I have observed your manners likewise lacking on many occasions on this website before. Your opinion of the matter is not well qualified. You're being an ass. Knock it off.

                        I realize you're probably not accustomed to being called on your lousy behavior. I doubt you will need to become so. But just for once, here we are. You don't bother to find out what you're talking about before you speak and then you want your hand held on points that were already clarified, had you but bothered to catch up. I don't tolerate that in candidates, I won't tolerate it in colleagues, and I see no very pressing reason to tolerate it here.

                        • radicalriddler4d

                          You're like the caricature of what other social media platforms represent HN users to be.

                          • throwanem3d

                            Wait, I'm confused. Do you mean that I correspond with the caricature by which you're accustomed to see HN users represented, presumably not by themselves, on other social media platforms? Or do you mean instead that I correspond with a caricature of the caricatured representation that etc.? Your comment is ambiguous. Please clarify.

                          • throwanem3d

                            Not really, that's more like N-Gate (pbuh, rip) [1].

                            [1] http://n-gate.com/hackernews/

              • astrange5d

                Ever tried doing it in nginx? You'll find `add_header` doesn't work at all the way you think it does.

                And it doesn't allow overrides in dotfiles since that's not performant or secure.

      • js25d

        There was also server[-side] push:

        https://www.oreilly.com/openbook/cgi/ch06_06.html

    • skrebbel5d

      I can’t wait till they hear about framesets

    • dlazaro5d

      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.

      • throwanem5d

        Oh, don't worry about it at all, and I don't just mean in my own case. Every generation learns to age graciously or otherwise, partly through experience, and for me it's a regular source of joy to see you young 'uns independently rediscover things I long since quit bothering to remember.

        • phatskat5d

          Honestly it’s kind of cute, I had all but forgotten about http-equiv

  • nhinck35d

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

    • dlazaro5d

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

      • nativeit5d

        I was just thinking about how to slice up a star map projection, and apply it as an overlay. I don’t do such things often enough to do it quickly, although I can imagine how it could be achieved. I’d imagine someone working in game dev probably could whip up a mechanism for applying coordinates to a star map fairly quickly, but realizing it in pure CSS would probably require exporting all the slices to a folder as SVG squares that are labeled with coordinates, and then using a bit of JS to stitch it all together in the rendered page.

        • mpetroff5d

          I wrote a simple web-based night sky viewer a while ago [1], which renders the 750 brightest stars from coordinates in a data file (along with the moon). It uses D3.js to do fully client-side SVG-based rendering for interactive use, but it could be simplified to render server side to an SVG file. I think the main complication is that by adding stars, a projection needs to be decided on, and you'd need to consider the aspect ratio of the browser window.

          [1] https://github.com/mpetroff/nightsky

    • socalgal25d

      Suggestion for the author, I don't think there are any outdoor places where the sky is black. I don't know that gray would be any better. Stars? Some night clouds? or maybe even still a gradient?

      https://www.google.com/search?sca_esv=58e7983bf9f21fcd&udm=2...

  • jclarkcom5d

    Very cool. We are launching a sensor that mounts on the inside of your window and measure the sky color for a small cone of the sky and transmits this to our skylight and window fixtures inside (see innerscene.com) so they can replicate exactly the same thing indoors. You could potentially use a computer monitor to do this, but it generally doesn't provide great light due to using RGBs instead of wide-spectrum sources.

    One issue with the current code is it doesn’t model clouds, haze, or smoke so the rendered sky can differ from what you see outside (numerous HN comments notice this). You can partially correct for this by using semi-realtime satellite imaging but hard to get super accurate which is what pushed us to develop our own sensor. There are various CCT sensors on the market already but they only measure directional+diffuse+reflected light which is typically ~7500k but the sky color goes up to 40,000k.

    Here is a plot showing the color of the sky as it changes during the day from real sensor readings. Each one is 30s apart, so it change change quickly. https://www.innerscene.com/built_pages/cs_specsheet/cct/cct_...

    A bit more info as well: https://www.innerscene.com/SpecHelp/CircadianSky/cct/cct.htm...

  • cloudfudge5d

    As an old-timer who's not up on all the latest whiz-bang web stuff, I have to ask what is the astro/cloudflare/wrangler magic that allows the following to work:

      const { latitude = "0", longitude = "0" } = Astro.locals.runtime.cf || {};
    
    I gather you're using some cloudflare feature wrapped in astro to provide lat/long but I don't see the actual plumbing that gets it to you (and I did try to spelunk through a decent amount of documentation to find it). Can you elaborate?
    • dlazaro5d

      There is no visible plumbing because it kinda is magic! Astro provides adapters for different server runtimes (e.g., Vercel, Cloudflare, Netlify), and it's basically just plug and play. The Cloudflare adapter exposes a bunch of bindings [1] through `Astro.locals.runtime`, which can be accessed during each request. The `cf` binding contains incoming request properties [2], including latitude and longitude.

      These bindings (or at least some of them) are also mocked when developing locally, in a non-Cloudflare-Workers environment.

      [1] https://developers.cloudflare.com/workers/wrangler/api/#supp...

      [2] https://developers.cloudflare.com/workers/runtime-apis/reque...

      • Theodores4d

        Any ideas on how to do this without the Cloud flare magic, so entirely in the client? Just based on time will suffice, with latitude approximated to somewhere such as London?

      • cloudfudge5d

        Great explanation; thanks.

    • gregsadetsky5d

      You can enable a feature in Cloudflare which will inject the approximate user's lat/lng (based on their IP (and other factors?)) as an HTTP header added to the original request:

      https://developers.cloudflare.com/network/ip-geolocation/

      "This Managed Transform adds HTTP request headers with location information for the visitor's IP address, such as city, country, continent, longitude, and latitude."

  • mourner5d

    Author of Suncalc here — this is exactly the kind of stuff I love to see my code being used in, thanks for sharing!

    • gregsadetsky5d

      Hey, small note that your excellent https://suncalc.net/ is showing an error due to the Google Maps API token having expired.

      I know that you deeply know map tech :-) but if I may make a suggestion - you might consider switching from Google Maps to Protomaps? https://github.com/protomaps/protomaps-leaflet

      Cheers

      • mourner5d

        Yeah, I think I last updated that website even before I released the first version of Leaflet. Life is very hectic at the moment, but I do really want to get to it sooner than later and modernize everything.

    • sheerun5d

      Author or contributor? Great work, by the way, I love such shows

  • esafak5d

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

  • 1010085d

    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

  • jaharios5d

    I refreshed the page, enabled js, refreshed again and again and finally I gave up thinking it is not loading because it was hugged to death. While reading the comments here it dawned on me that it was just a black background because it is night outside and the paged worked fine from the start...

  • SeanAnderson5d

    Oh nice, this is actually something I very specifically wanted for https://ant.care/! I was trying to have the background sky for the ant farm be reflective of the user's current environment, but I didn't do anything more than a naïve approach. Maybe I'll work on adopting your approach at some point :) Still a bit torn on if the whole thing should be Rust/WASM or just the core simulation in Rust and defer as much as possible to JS/HTML.

  • xattt5d

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

    • fudged715d

      It would be awesome for a fake window in a basement

  • fmbb5d

    It’s way too dark for this time of year at this time of day here at 60 degrees north.

    But it looked very cool earlier today when it matched!

  • joeyh5d

    This reminds of of a web page that did this for Ithaca NY circa 1995. The page was a static hardcoded shade of grey.

  • cgijoe5d

    Ooh, how about this as a live desktop wallpaper!

  • nisten5d

    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

  • ianbicking5d

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

    I wonder what it would take to account for weather?

    • craftkiller5d

      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.

  • card_zero5d

    Useful, saves me looking at the thing.

  • fastasucan5d

    This might be a stupid question, but is it the background of https://html.energy/html-day/2025/index.html that shows the current sky? I am a bit confused since neither the post or the github repo says so outright.

    Edit: I think its this link: https://sky.dlazaro.ca/ OP - put it in the HN post and first on your github repo! Good work.

  • kylegalbraith5d

    Tid bits like this are why HN is still the best corner of the internet most of the time.

    This is really cool. I’ll probably see if I can make it my new tab background in Chromium.

  • leokennis5d

    Should anyone appreciate it, this Shortcut for your iOS/iPadOS device will set your wallpaper to the current sky based on this nice tool:

    https://www.icloud.com/shortcuts/c8ba254a0272453cbe39357b144...

    Just make sure that your last (or only) iDevice Home Screen is set to type “image”.

  • yonatan80705d

    Very cool, though I opened it at night so it's just black. Is there a way to adjust the time it renders to see what it would look like at different times?

  • bigwheels3d

    Tried this out now- it's totally gray outside as far as the eye can see, but the sky.dlazaro.ca shows it as clear blue. I wonder where the disconnect / divergence is originating from! Super neat idea in concept :)

  • ryukoposting5d

    Would be cool if it considered current weather conditions. The sky is presently much grayer than what the site showed me.

  • Biganon5d

    Not often does a project make me think "adorable", and it's a compliment. Just lovely.

  • mushufasa5d

    would love this to be a desktop background -- linux or macOS

  • j455d

    Neat tool, would love to be able to set the location when the registered IP location isn’t accurate.

  • tinco5d

    21pm in The Netherlands, the sky is a clear blue down to a baby pink right now, however the app shows a black to dark red. Other people are saying it matches exactly for their location so maybe there's some sort of bug?

    • croisillon5d

      during the day it was good here, now that it is night it's a bit off for me too

  • cosmicgadget5d

    That is awesome but now I want to check what my SF bros see when they look up.

  • dddgghhbbfblk5d

    I'll have to check this out tomorrow. I can tell you that black is not very accurate for my current conditions (midnight in Manhattan) but curious to see how it does in the day!

  • tcumulus5d

    Very cool! Might be interesting to combine this with cloud data or sunset forecast data from Sunsethue to create some sort of sky/sunset simulation. Well done!

  • CodeVerseEx4d

    Very cool concept. Would be great if there’s an option to tweak the gradient before copying, so devs can match it exactly to their design needs.

  • meatjuice5d

    This project looks amazing and fun. However, the website did not seem to take the cloudy weather at my current location into account, which is a bit of a disappointment.

  • djoldman5d

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

        <body style={{backgroundColor: bottom}}> </body>
    
    is not needed.
  • dehugger5d

    Is this all done server side? I was shocked to inspect the page to discover zero js or even a stylesheet. Not so much as a single div. Very impressive.

  • mgdm5d

    I have been meaning to do it for ages! I got as far as finding a paper on the topic and reading it and then forgetting all about it. Nice work.

  • jama2114d

    This would be cool on a fake window for your house, like a screen in a basement

  • DonHopkins5d

    Why doesn't it respect dark mode??? ;)

  • 2OEH8eoCRo04d

    My sky is blue and orange right now though and your site shows black.

  • stephenlf5d

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

    • verandaguy5d

      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).

  • jhardy545d

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

  • mcintyre19945d

    This is really cool! And from skimming your code, TIL about Math.hypot!

  • gdubs5d

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

  • jama2115d

    Ok this is incredible, it was exactly right, I did a double take!

  • chrz4d

    Fully black web page for me here. Well its correct

  • cwmoore5d

    I like this, but I’m newly concerned about the unitary horizon.

  • ComputerGuru5d

    Ahhh you’re not taking light pollution into account!

  • mlhpdx5d

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

    • dlazaro5d

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

  • verelo5d

    Feels like this would be great for fake skylights…

  • sudosteph5d

    Looks pretty Carolina blue to me. Good job.

  • lazystar5d

    sunsetting in the monroe, wa area. only a month left to live out here, gonna miss it dearly

  • nnnnico5d

    incredible <3 not much else to say

  • sheerun5d

    Bit darker blues, please!

  • michelreij5d

    Beautiful, thank you!

  • i_love_retros5d

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

    • dlazaro5d

      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.

      • nnnnico5d

        it's beautiful. btw, could this be all done in client side js? didnt look at the implementation, probably server is used to resolve location?

        • wonger_5d

          (not author) from the source:

            const { latitude = "0", longitude = "0" } = Astro.locals.runtime.cf || {};
          
          To do it client-side, you would probably have to call some less-reputable IP geolocation service, or settle for navigator.geolocation which has a permission popup
          • mcteamster5d

            Depending on how "approximate" is acceptable, I've found that using timezone names can be a good proxy for location. As most users have their timezones set correctly it's more consistent and private than IP or GPS.

            I've made a library for my own use cases that does this (https://github.com/mcteamster/virgo), but it's also pretty straightforward to parse the city/state name out of the timezone and look it up somewhere.

    • ascorbic5d

      Astro is a great way to write HTML

      • dlazaro5d

        I'm sure that's your totally unbiased opinion ;)

        • ascorbic5d

          I was a fan of Astro long before I became a maintainer. That's why I joined!

  • natewww5d

    that is really cool, thanks for sharing

  • therealfiona5d

    Works in Hawaii.

  • hoppp5d

    Seems to work :)

  • siva75d

    how i missed this small hn posts. thanks