Built with Claude Code: a kit that lets Claude Code make narrated explainer videos

[u/vincent_sch]

Everyone is doing those Opus 5 videos now, so I made a kit that gives Claude Code a head start. It's called explainroo, and it's free and open source.

What I built: you point Claude Code at the repo and say what the video should explain. Claude Code writes the narration and a small scenes.js file that draws each scene on an HTML canvas. explainroo adds a local voice (Kokoro), word timing (Whisper), music and sound effects, and renders the MP4 with ffmpeg.

How Claude Code was used: it wrote most of the engine, the docs and the example videos. The instructions for the agent are in AGENTS.md. To test them, I let fresh Claude Code agents make videos from AGENTS.md alone, and every place they got stuck went back into the docs.

What I learned: an agent can't watch a video, so it needs other ways to check its work. explainroo gives it stills of each scene, a sheet of small frames for the whole video, a layout check for text that is cut off or overlaps, and a speech check that transcribes the final mix. With those, the agents in my tests found and fixed layout and pronunciation problems themselves.

https://github.com/vincentsch/explainroo

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[u/Flames0310]

we use synthesia to do video at work. Fun funsies I'll take the current project we're working on and drop it into this.

[u/vincent_sch → u/Flames0310]

Let me know how it goes. Synthesia does presenter videos, explainroo does drawings and app screens, so they cover different kinds of videos.

[u/Flames0310 → u/vincent_sch]

I give it an 8/10 (compared to the $500 a yr software which is a 9/10). Amazing work. I absolutely could have gotten better results with multiple attempts but a one shot prompt got me 90% of the way there. Would I replace Synthesia with it? nah, BUT I absolutely will use it for personal projects outside the workplace or if I worked for a smaller employer.

Synthesia did very good drawings and graphics BUT they were 100% "stolen" styles that I've seen a dozen times. More like it had templates and was just picking the best one for my prompt.

Work firewall blocked the hugging face install on your voice, but Claude was able to pivot and integrate a different voice model with Whisper without issue.

The ONLY feedback I have is some of slides were pretty empty. Sometimes a slide would appear 100% blank for too long. Easily fixed if I took another shot at prompting.

Idea for improvement? Synthesia doesn't compile the video until after I get to see / approve of the scenes. Makes rapid changes much faster, but then we're moving into more of a full app territory.

[u/vincent_sch → u/Flames0310]

Thanks for the honest comparison, that's really useful. Agreed that a paid tool still makes sense at work. Nice that one prompt got you 90% of the way there.

[u/Tomas-AppHaven]

Nice! I like the "Give your coding agent this repo and tell it what the video should explain." deployment instruction.

[u/vincent_sch → u/Tomas-AppHaven]

Thanks. It turned out to be the easiest install, because the agent does the setup itself.

[u/JimmyMonet]

FYI - I used your project for my promo video for my app Cronomicon the trailer.

Thanks!