The best Hacker News stories from Show from the past day
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Show HN: Cynthia – Reliably play MIDI music files – MIT / Portable / Windows
Easy to use, portable app to play midi music files on all flavours of Microsoft Windows.<p>Brief Background - Used midi playback way back in the days of Windows 95 for some fun and entertaining apps, but as Windows progressed, it seemed their midi support (for Win32 anyway) regressed in both startup speed and reliability. Midi playback used to be near instant on Windows 95, but on later versions of Windows this was delayed to about 5-7 seconds. And reliability became somewhat patchy. This made working with midi a real headache.<p>Cynthia was built to test and enjoy midi music once again. It's taken over a year of solid coding, recoding, testing, re-testing, and a lot more testing, and some hair pulling along the way, but finally Cynthia works pretty solidly on Windows now.<p>Some of Cynthia's Key Features:
* 25 built-in sample midis on a virtual disk - play right out-of-the box
* Play Modes: Once, Repeat One, Repeat All, All Once, Random
* Play ".mid", ".midi" and ".rmi" midi files in 0 and 1 formats
* Realtime track data indicators, channel output volume indicators with peak hold, 128 note usage indicators
* Volume Bars to display realtime average volume and bass volume levels
* Use an Xbox Controller to control Cynthia's main functions
* Large list capacity for handling thousands of midi files
* Switch between up to 10 midi playback devices in realtime
* Playback through a single midi device, or multiple simultaneous midi devices with lag and channel output support
* Custom built midi playback engine for high playback stability
* Custom built codebase for low-level work to GUI level
* Also runs on Linux/Mac (including apple silicon) via Wine
* Smart Source Code - compiles in Borland Delphi 3 and Lazarus 2
* MIT License<p>YouTube Video of Cynthia playing a midi:
<a href="https://youtu.be/IDEOQUboTvQ" rel="nofollow">https://youtu.be/IDEOQUboTvQ</a><p>GitHub Repo:
<a href="https://github.com/blaiz2023/Cynthia" rel="nofollow">https://github.com/blaiz2023/Cynthia</a>
Show HN: OCR Arena – A playground for OCR models
I built OCR Arena as a free playground for the community to compare leading foundation VLMs and open-source OCR models side-by-side.<p>Upload any doc, measure accuracy, and (optionally) vote for the models on a public leaderboard.<p>It currently has Gemini 3, dots.ocr, DeepSeek, GPT5, olmOCR 2, Qwen, and a few others. If there's any others you'd like included, let me know!
Show HN: OCR Arena – A playground for OCR models
I built OCR Arena as a free playground for the community to compare leading foundation VLMs and open-source OCR models side-by-side.<p>Upload any doc, measure accuracy, and (optionally) vote for the models on a public leaderboard.<p>It currently has Gemini 3, dots.ocr, DeepSeek, GPT5, olmOCR 2, Qwen, and a few others. If there's any others you'd like included, let me know!
Show HN: OCR Arena – A playground for OCR models
I built OCR Arena as a free playground for the community to compare leading foundation VLMs and open-source OCR models side-by-side.<p>Upload any doc, measure accuracy, and (optionally) vote for the models on a public leaderboard.<p>It currently has Gemini 3, dots.ocr, DeepSeek, GPT5, olmOCR 2, Qwen, and a few others. If there's any others you'd like included, let me know!
Show HN: Stun LLMs with thousands of invisible Unicode characters
I made a free tool that stuns LLMs with invisible Unicode characters.<p>*Use cases:* Anti-plagiarism, text obfuscation against LLM scrapers, or just for fun!<p>Even just one word's worth of “gibberified” text is enough to block most LLMs from responding coherently.
Show HN: Stun LLMs with thousands of invisible Unicode characters
I made a free tool that stuns LLMs with invisible Unicode characters.<p>*Use cases:* Anti-plagiarism, text obfuscation against LLM scrapers, or just for fun!<p>Even just one word's worth of “gibberified” text is enough to block most LLMs from responding coherently.
Show HN: I built an interactive HN Simulator
Hey HN! Just for fun, I built an interactive Hacker News Simulator.<p>You can submit text posts and links, just like the real HN. But on HN Simulator, all of the comments are generated by LLMs + generate instantly.<p>The best way to use it (IMHO) is to submit a text post or a curl-able URL here: <a href="https://news.ysimulator.run/submit" rel="nofollow">https://news.ysimulator.run/submit</a>. You don't need an account to post.<p>When you do that, various prompts will be built from a library of commenter archetypes, moods, and shapes. The AI commenters will actually respond to your text post and/or submitted link.<p>I really wanted it to feel real, and I think the project mostly delivers on that. When I was developing it, I kept getting confused between which tab was the "real" HN and which was the simulator, and accidentally submitted some junk to HN. (Sorry dang and team – I did clean up after myself).<p>The app itself is built with Node + Express + Postgres, and all of the inference runs on Replicate.<p>Speaking of Replicate, they generously loaded me up with some free credits for the inference – so shoutout to the team there.<p>The most technically interesting part of the app is how the comments work. You can read more about it here, as well as explore all of the available archetypes, moods, and shapes that get combined into prompts: <a href="https://news.ysimulator.run/comments.html" rel="nofollow">https://news.ysimulator.run/comments.html</a><p>I hope you all have as much fun playing with it as I did making it!
Show HN: I built an interactive HN Simulator
Hey HN! Just for fun, I built an interactive Hacker News Simulator.<p>You can submit text posts and links, just like the real HN. But on HN Simulator, all of the comments are generated by LLMs + generate instantly.<p>The best way to use it (IMHO) is to submit a text post or a curl-able URL here: <a href="https://news.ysimulator.run/submit" rel="nofollow">https://news.ysimulator.run/submit</a>. You don't need an account to post.<p>When you do that, various prompts will be built from a library of commenter archetypes, moods, and shapes. The AI commenters will actually respond to your text post and/or submitted link.<p>I really wanted it to feel real, and I think the project mostly delivers on that. When I was developing it, I kept getting confused between which tab was the "real" HN and which was the simulator, and accidentally submitted some junk to HN. (Sorry dang and team – I did clean up after myself).<p>The app itself is built with Node + Express + Postgres, and all of the inference runs on Replicate.<p>Speaking of Replicate, they generously loaded me up with some free credits for the inference – so shoutout to the team there.<p>The most technically interesting part of the app is how the comments work. You can read more about it here, as well as explore all of the available archetypes, moods, and shapes that get combined into prompts: <a href="https://news.ysimulator.run/comments.html" rel="nofollow">https://news.ysimulator.run/comments.html</a><p>I hope you all have as much fun playing with it as I did making it!
Show HN: I built an interactive HN Simulator
Hey HN! Just for fun, I built an interactive Hacker News Simulator.<p>You can submit text posts and links, just like the real HN. But on HN Simulator, all of the comments are generated by LLMs + generate instantly.<p>The best way to use it (IMHO) is to submit a text post or a curl-able URL here: <a href="https://news.ysimulator.run/submit" rel="nofollow">https://news.ysimulator.run/submit</a>. You don't need an account to post.<p>When you do that, various prompts will be built from a library of commenter archetypes, moods, and shapes. The AI commenters will actually respond to your text post and/or submitted link.<p>I really wanted it to feel real, and I think the project mostly delivers on that. When I was developing it, I kept getting confused between which tab was the "real" HN and which was the simulator, and accidentally submitted some junk to HN. (Sorry dang and team – I did clean up after myself).<p>The app itself is built with Node + Express + Postgres, and all of the inference runs on Replicate.<p>Speaking of Replicate, they generously loaded me up with some free credits for the inference – so shoutout to the team there.<p>The most technically interesting part of the app is how the comments work. You can read more about it here, as well as explore all of the available archetypes, moods, and shapes that get combined into prompts: <a href="https://news.ysimulator.run/comments.html" rel="nofollow">https://news.ysimulator.run/comments.html</a><p>I hope you all have as much fun playing with it as I did making it!
Show HN: I built an interactive HN Simulator
Hey HN! Just for fun, I built an interactive Hacker News Simulator.<p>You can submit text posts and links, just like the real HN. But on HN Simulator, all of the comments are generated by LLMs + generate instantly.<p>The best way to use it (IMHO) is to submit a text post or a curl-able URL here: <a href="https://news.ysimulator.run/submit" rel="nofollow">https://news.ysimulator.run/submit</a>. You don't need an account to post.<p>When you do that, various prompts will be built from a library of commenter archetypes, moods, and shapes. The AI commenters will actually respond to your text post and/or submitted link.<p>I really wanted it to feel real, and I think the project mostly delivers on that. When I was developing it, I kept getting confused between which tab was the "real" HN and which was the simulator, and accidentally submitted some junk to HN. (Sorry dang and team – I did clean up after myself).<p>The app itself is built with Node + Express + Postgres, and all of the inference runs on Replicate.<p>Speaking of Replicate, they generously loaded me up with some free credits for the inference – so shoutout to the team there.<p>The most technically interesting part of the app is how the comments work. You can read more about it here, as well as explore all of the available archetypes, moods, and shapes that get combined into prompts: <a href="https://news.ysimulator.run/comments.html" rel="nofollow">https://news.ysimulator.run/comments.html</a><p>I hope you all have as much fun playing with it as I did making it!
Show HN: PolyGPT – ChatGPT, Claude, Gemini, Perplexity responses side-by-side
I built PolyGPT to solve a problem I had: constantly tab-switching between ChatGPT, Claude, and Gemini to
compare their responses.<p><pre><code> It's a desktop app (Mac/Windows/Linux) that lets you type a prompt once and see all three AI models respond
simultaneously in a split view. Useful for:
- Comparing technical explanations
- Getting multiple perspectives on code problems
- Fact-checking answers across models
The app is free, open source, and runs locally - your credentials stay on your machine.
Download: https://polygpt.app
Source: https://github.com/ncvgl/polygpt
Would love feedback from the HN community. What other features would make this more useful?</code></pre>
Show HN: A tool to safely migrate GitHub Actions workflows to Ubuntu-slim runner
Hi HN!<p>I’ve been running GitHub Actions workflows for a while, and when GitHub announced the new ubuntu-slim runners as a cheaper alternative to ubuntu-latest, I wanted to migrate—but figuring out which workflows are safe to switch turned out to be surprisingly tedious.<p>You need to check for Docker usage, services, containers, step failures due to missing packages, and whether jobs rely on tools not available in the slim image.<p>So I built gh-slimify, a GitHub CLI extension that automates all of this. It scans your repository, detects which jobs can be migrated, flags incompatible patterns, identifies missing commands, and can update only the safe workflows with a single command.<p>gh extension install fchimpan/gh-slimify
gh slimfy # Analyze workflows
gh slimfy fix # Update only jobs that are safe to migrate<p>It’s open source (MIT).
As a bonus: the README also includes an AI agent prompt that reproduces the same workflow-migration analysis—useful if you want to integrate the logic into an LLM agent or experiment with automated refactoring.<p>I’d love feedback—especially on edge cases, false positives/negatives, or patterns it should detect better.
Show HN: I wrote a minimal memory allocator in C
A fun toy memory allocator (not thread safe, that's a future TODO). I also wanted to explain how I approached it, so I also wrote a tutorial blog post (~20 minute read) covering the code which you can find the link to in the README.
Show HN: I wrote a minimal memory allocator in C
A fun toy memory allocator (not thread safe, that's a future TODO). I also wanted to explain how I approached it, so I also wrote a tutorial blog post (~20 minute read) covering the code which you can find the link to in the README.
Show HN: I wrote a minimal memory allocator in C
A fun toy memory allocator (not thread safe, that's a future TODO). I also wanted to explain how I approached it, so I also wrote a tutorial blog post (~20 minute read) covering the code which you can find the link to in the README.
Show HN: Gitlogue – A terminal tool that replays your Git commits with animation
Gitlogue is a CLI that turns your Git commits into a typing-style replay.<p>It visualizes diffs line by line, shows the file tree, and plays back each edit as if it were typed in real time.<p>Key points<p>• Realistic typing animation<p>• Syntax-highlighted diffs<p>• File-tree view<p>• Replay any commit<p>• Self-contained CLI<p>Demo video is in the README.<p>Repo: <a href="https://github.com/unhappychoice/gitlogue" rel="nofollow">https://github.com/unhappychoice/gitlogue</a>
Show HN: Gitlogue – A terminal tool that replays your Git commits with animation
Gitlogue is a CLI that turns your Git commits into a typing-style replay.<p>It visualizes diffs line by line, shows the file tree, and plays back each edit as if it were typed in real time.<p>Key points<p>• Realistic typing animation<p>• Syntax-highlighted diffs<p>• File-tree view<p>• Replay any commit<p>• Self-contained CLI<p>Demo video is in the README.<p>Repo: <a href="https://github.com/unhappychoice/gitlogue" rel="nofollow">https://github.com/unhappychoice/gitlogue</a>
Show HN: Vibe Prolog
Like a lot of people I got the $250 Claude Code credit and didn't use it up.<p>I decided to try to use it up over the weekend using (mostly) my phone and vibe coded a Prolog interpreter.<p>Now I'm seeing how far I can push it.
Show HN: Vibe Prolog
Like a lot of people I got the $250 Claude Code credit and didn't use it up.<p>I decided to try to use it up over the weekend using (mostly) my phone and vibe coded a Prolog interpreter.<p>Now I'm seeing how far I can push it.
Show HN: I built a wizard to turn ideas into AI coding agent-ready specs
I created vibescaffold.dev. It is a wizard-style AI tool that will guide you from idea → vision → tech spec → implementation plan. It will generate all the documents necessary for AI coding agents to understand & iteratively execute on your vision.<p>How it works:
- Step 1: Define your product vision and MVP
- Step 2: AI helps create technical architecture and data models
- Step 3: Generate a staged development plan
- Step 4: Create an AGENTS.md for automated workflows<p>I've used AI coding tools for awhile. Before this workflow (and now, this tool), I kept getting "close but not quite" results from AI coding tools. I learned that the more context & guidance I gave these tools up front, the better results I got.<p>The other thing I have found with most tools that attempt to improve on "vibe coding" is that they add abstraction. To me, this just adds to the problem. AI coding agents are valuable, but they are error-prone - you need to be an active participation in their work. This workflow is designed to provide a scaffolding for these AI agents, while minimizing additional abstraction.<p>Would love feedback on the workflow - especially curious if others find the upfront planning helpful or constraining.