Show HN: Knowthemat.com a free site I vibe-coded to help you learn BJJ rules

1 vcarrico 0 8/7/2025, 12:37:03 PM knowthemat.com ↗

Hey HN,

Any fellow BJJ folks around? o/

So, last week I registered for my first BJJ competition, and while reading the IBJJF rulebook, I realized I’m not as familiar with it as I thought. So, I decided to “vibe-code” this app to generate quizzes based on different rulesets (IBJJF, ADCC, AJP).

It’s very simple: 1. You choose the ruleset (example: IBJJF) 2. Pick the topics you want to focus on (Points Scoring, Advantages) 3. Select the number of questions 4. That’s it — it gives you a quick quiz with multiple-choice questions pulled from the official rulebook.

If you try it out, I’d love to hear some honest opinions. Just letting me know if you find it useful.

Some technical details: * All the questions are pre-generated by AI, not created on the fly. I’ll probably keep adding more and maybe focus on situational type of questions. * I completely vibe-coded this using vscode and copilot in agent mode with Claude Sonnet 4. It’s impressive how fast it could prototype and make it grow until the point I was almost lost in my own project!

[]s

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Show HN: Knowthemat.com a free site I vibe-coded to help you learn BJJ rules

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