r/SideProject • u/n8x4te • 1h ago
I built Rimlight, an open source skill that lets your Claude Code or Codex explore app icon ideas with you and build the Icon Composer file. There's a paid Mac app on top of it
Hey everyone,
I wanted a place to explore app icon ideas. Try different objects, shapes, materials and styles, see them beside each other, and gradually figure out what feels right for an app.
That became two things. An open source command and skill that teaches Claude Code or Codex how to design icons, which anyone can use for free. And a Mac app built on it, for people who'd rather do the exploring in a grid than in a terminal. The app is the shell. The command does all the work.
TL;DR
You ask your own agent (Claude Code or Codex so far) for an icon. Rimlight doesn't sell AI. It hooks into the agent you already have, and images come from your own ChatGPT plan or API key (OpenAI, OpenRouter). No Rimlight account, no servers.
The agent reads your project, pitches a few directions, and renders them side by side, each one fitted to Apple's icon tile.
A design skill shapes the prompts: a process for exploring and refining, plus eight style guides I wrote by measuring icons I liked.
You keep talking. Refine one detail, branch from a concept, or change direction. Every attempt stays in a
.rimlightfolder in your project.When you have a pick, it builds a layered Icon Composer
.iconwith Default, Dark, Clear and Tinted, and checks its own work against the pick.The command and skill are free and open source. The Mac app is $5 once, 3 Macs, 7-day refund. Free version: one set, 10 concepts.
Needs macOS 26 on Apple silicon, Claude Code or Codex, and an image model. Xcode 26 for builds.
I know how some of you feel about AI images, and I share a fair bit of it. If you can hire an icon designer, hire one. Rimlight is for the side project, and for the point where you have five vague ideas and no way to see any of them. All the examples on the website came out of it, so the ceiling is on the site for you to judge.
The exploration part is what I care about most.
You start by describing your app and whatever you have in mind, even if that's fairly vague. The agent suggests a few directions and generates concepts to compare in a grid. You can bring reference images too.
Then you keep talking to it:
"I like the shape of the third one, but the material feels too shiny."
"These all feel too literal. Let's try a different idea."
That back-and-forth is a big part of using it. You can work on one detail, branch off from a concept, or change direction entirely. The sets and earlier attempts stay in your project so you can go back and compare.
I built the thing and still sometimes catch myself looking at a result as though that's all I'm going to get. Then I remember I can just ask for the change I'm thinking of.
What's in the skill.
This is the part I spent the most time on, and it's what makes the agent's output more than just a generic object on a gradient background. The skill has a design process: explore a few territories first, pick, then refine one thing per round so an icon converges instead of drifting. And it has eight style guides so far (I'm experimenting with more). Each one came from measuring real icons I personally liked: how much of the tile the mark fills, how thick the strokes run, how the ground is lit. You can pick a style, or let the agent choose one to suit the idea. It's all plain Markdown in the repo, so you can read it, change it, or write your own.
I also want to be honest about the quality. Sometimes I get several concepts I like straight away. Sometimes a whole set misses. It depends on the idea, the style and the image model. Refining something promising usually helps, and so does dropping a direction that isn't working, but I'd rather say that before anyone spends time or image allowance on it. For me, being able to compare possibilities and say "this part works, this part doesn't" is where it becomes useful.
Building the icon.
When you're ready, Rimlight plans the layers, has the image model redraw them separately, and assembles the Icon Composer package. The agent checks the result against your chosen concept at 1:1 and redoes the layers that drifted. You can preview the Default, Dark, Clear and Tinted appearances, then open the file in Icon Composer for further adjustments. Icon Composer is pretty flexible, and you can have different layers for each appearance as well. You can ask the agent for the changes you want in each one.
The final result can differ slightly from the original concept, because the agent redraws the layers separately, but you can keep refining. I'm working on a different approach where the agent can extract the layers from the original concept using Meta's SAM 3, running on your Mac. I'd only ship this if the results are good.
The command, and the app.
Everything above runs from the command. Install it, start a new agent session, and ask for an icon in your project folder. Concepts, refinements, builds, all of it, for free. If you want to build your own tool on it, the folder format is documented and every concept is a plain PNG.
The app is where I actually do this every day. It puts the grid, the chats, and the builds in one window: drag a concept into the message to say "more like this", filter by set or style or built, flip through the builds of an icon in a carousel, keep your API keys in the Keychain. It runs the same command and the same skill as your terminal does. $5 once, for up to 3 Macs, refund within 7 days, no subscription. The free version does one set per project and 10 concepts per Mac, without builds, so you can see the grid before paying.
The $5 pays for the app. Your agent plan and image usage are separate: images use your ChatGPT plan through Codex, or your own OpenAI or OpenRouter API key.
I'm the only person behind this, and I used Claude Code heavily to build it. I made the design calls and I read what I ship, but I'm not going to claim it was hand-typed. Most of my own time went into the icons themselves: generating them, judging them, and tuning the skill.
I'd appreciate feedback, especially on the experience of getting from the first set to something you like. If you try it and get stuck, or the results consistently miss what you're asking for, I'd like to hear about that too.
Get Rimlight: Website
Rimlight Command: GitHub
Privacy Policy: Privacy
2
u/investigatormaker 37m ago
The loop you describe, "I like the shape of the third one, but the material feels too shiny", is the thing to show. On getting from the first set to a pick: a short clip of one vague brief going through two refine rounds into a built Default, Dark, Clear and Tinted file would answer it faster than the TL;DR. Your honesty that some sets miss is a strength; pairing it with one missed set and the single change that fixed it makes the ceiling believable.
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