Constell does this in a "cosmic" way by turning a webpage into a drifting space scene with stars, nebula clouds, subtle mouse movement interactivity, and the occasional shooting star.

What Is Constell?

Constell is a self contained animated background component built with JavaScript and the HTML canvas element along with css to fancy it up. You give it a canvas, initialize it, and it handles drawing and animating the scene behind the rest of your page. It is just a background effect that is easy to add, easy to customize, and easy to remove if you eventually decide outer space was a questionable design decision.

There is no framework required, no build process, and no runtime dependency. The main pieces are constell.js for the actual rendering and animation, and an optional constell.css file that gives you page styling and theme variables.

Constell is running on this post, so the stars and motion behind these words are the same code this post is about. Change up the theme (top of this page) to see how it looks in dark/light modes.

What Does It Actually Do?

The background is made from several small effects working together instead of one giant LOOK AT ME animation. The result is movement that is noticeable without constantly fighting your actual page content for attention.

Constell includes:

• Stars with different sizes, brightness levels, depths, drift speeds, and twinkle behavior
• Soft nebula clouds that slowly move behind the stars
• Mouse based parallax that gives the scene a little depth
• Random shooting stars that occasionally streak across the screen
• Dark, light, and system theme support
• Runtime configuration so the scene can be adjusted after it starts

The star depth is probably one of the more important pieces visually. Stars at different depths move and render differently, which keeps the background from looking like somebody sprinkled white pixels on a canvas and called it space.

The parallax helps with that too. Moving the mouse creates a small shift through the scene, enough to make the layers feel separated without turning the webpage into one of those old desktop screensavers that made everyone seasick.

The Nice Part, It Is Just JavaScript

One thing I wanted with Constell was for it to be easy to drop into a normal webpage. I did not want somebody to need React, Vue, three package managers, a spiritual relationship with Node, and a Saturday afternoon just to get some stars moving around.

At the simplest level, the setup looks something like this:

<link rel="stylesheet" href="constell.css" />

<canvas id="scene"></canvas>

<script type="module">
    import { Constell } from "./constell.js";

    Constell.init("#scene");
</script>

That is the basic idea. Put the files in your project, add the canvas, initialize Constell, and your webpage now has considerably more outer space than it had five minutes ago.

Because constell.js is an ES(ECMAScript) module, the page needs to be served through a web server instead of opened directly as a local file. If you are already building a website, you are probably doing that anyway.

Run The Included Demo

The repo includes an index.html file whose main job is to be a working demo. It gives you a complete page you can run immediately, with the animated canvas, some example configuration, and a theme toggle already wired up. Before copying pieces into your own site, it is probably worth running that page once so you can see what everything is supposed to do when nobody has broken it yet.

To get the demo running on your machine, clone the repo, move into the folder, and start a small local web server:

git clone https://github.com/emo333/constell.git
cd constell
python -m http.server 7070

Then open http://localhost:7070 in your browser. You should see the included index.html demo running Constell, complete with the animated background and theme button. From there you can open index.html, constell.js, and constell.css side by side and start seeing how the pieces fit together.

If Python is not part of your normal setup, any static web server is fine. The important part is serving the folder over HTTP because the JavaScript is loaded as an ES module. The README includes a few other options if your preferred method of starting a tiny web server is different.

It Is Configurable, But This Is Not The Manual

The defaults are meant to give you a usable scene immediately, but there is quite a bit you can change. Star count, colors, motion speed, parallax sensitivity, glow, nebula behavior, shooting stars, background colors, and other visual details can all be adjusted.

You can pass settings when Constell starts:

Constell.init("#scene", {
    star: {
        count: 70
    },
    motion: {
        speed: 4
    }
});

You can also change settings while it is already running. That makes it possible to connect Constell to controls on your page, user preferences, or whatever weird experiment you are currently convincing yourself is absolutely necessary.

I am intentionally not dumping the entire configuration reference into this post. The Constell README has the full list of options, defaults, examples, theme configuration, and more detailed setup instructions.

Use It As A Starting Point For Your Own Animated Background

You also do not have to use Constell exactly as I wrote it. One of the reasons I kept the project fairly small and dependency free is that the JavaScript is approachable enough to open up, poke around, and start changing things without first needing a map of the map.

If you like the general idea but stars are not your thing, dig into constell.js and start experimenting. Change how particles are drawn, replace the nebula effect, alter the movement, make objects react differently to the mouse, or remove entire pieces and build something completely different on top of the same basic canvas setup.

That is probably one of the more useful ways to look at this project. Constell can be the finished background you drop into a site, but it can also be a starting point for learning how a canvas animation is put together and then turning it into your own thing. Break it, change it, make it weird, then act like the weird part was intentional from the beginning.

Even better, throw it in a AI coding harness and ask an LLM to do what you want with it.

Dark Mode, Light Mode, And System Mode

Constell supports dark, light, and system themes. The canvas scene itself changes along with the supporting CSS, so switching themes does not leave you with a light webpage floating over a giant dark hole in space.

System mode can follow the operating system preference and react when that preference changes. If your site already has its own theme switcher, Constell can also be connected to that instead of trying to become the boss of your entire color scheme.

This was important because animated backgrounds are already dangerously close to being decorative nonsense. At minimum, the decorative nonsense should match the rest of the website.

Motion Without Making The Page Annoying

There are a lot of ways to make an animated background technically impressive and visually terrible. I wanted the default behavior to stay on the calmer side, with slow movement, soft glows, and shooting stars that show up occasionally instead of attacking the screen every twelve milliseconds.

The overall animation speed can be changed, and the motion behavior can be reduced or frozen through configuration when needed. You can also turn shooting stars off completely if meteors are somehow where you draw the line.

Since the scene is drawn on a canvas behind the normal page content, the actual website can remain normal HTML and CSS. Constell is decoration, your content is still your content, and the two do not need to become entangled like your power/data cables behind your desk.

Where I Think It Fits

Constell makes the most sense on pages where a little atmosphere helps the design. Personal sites, project pages, landing pages, portfolio pages, dashboards, or a simple static page can all use it without having to restructure the entire site around the effect.

It is probably not the thing I would put behind a 97 field insurance form. Context matters.

I also like that it can be subtle. You can slow things down, reduce the number of stars, tone down the nebula colors, or disable the shooting stars and use it as background texture instead of making SPACE the entire personality of the site.

The Pitch

Constell is not a graphics engine, it is not a game framework, and it is not trying to solve every animation problem on the web. It draws a nice animated "space" or "cosmic" background, gives you enough control to make it fit your site, and otherwise tries to stay out of your way. Pretty much plug-and-play.

If you want an animated constellation style background without pulling a pile of dependencies into your project, grab the files, initialize the canvas, tweak it until it looks right, and get back to building the actual website.

For the full setup instructions and all the knobs you can turn, read the README. There are enough knobs in there to keep you busy if the defaults make you barf.

Resources

• Constell on GitHub
• Constell README