Can I vibecode Rendemo?

KINDA · weekend project

price $39/moyou'd save $468/yrbuild time a weekendcategory 🎬 audio & videoreplaced by 0 people

The mechanics of a demo builder are not mysterious: capture or import clips, trim them, add zooms, captions and a background, then render an MP4. An agent can wire that up locally with ffmpeg and a canvas timeline in a weekend, and for a solo founder shipping one launch video that is probably enough. What it will not hand you is the taste baked into the presets: the easing on the auto-zoom, the mouse smoothing, the default padding that makes a raw screen recording look intentional. You also lose hosted playback, analytics on who watched, and the ability to re-render at 4K without your laptop fans screaming. Fine if you make demos occasionally, annoying if demos are your job.

the prompt

Build a local-only product demo video editor. No accounts, no cloud, no telemetry.

Stack, no substitutions:
- Vite + React + TypeScript
- Tailwind for UI
- Zustand for editor state
- fluent-ffmpeg driving a locally installed ffmpeg binary, via a small Express server on port 8787
- Projects stored as JSON files in ./projects, media in ./media

Features in scope:
1. Import: drag and drop .mp4 / .mov / .webm files, plus an in-app recorder using navigator.mediaDevices.getDisplayMedia that saves a .webm to ./media.
2. Timeline: single video track, drag to reorder clips, trim handles for in/out points, delete clip.
3. Keyframed zoom: user clicks a point on the preview at a given time and sets a zoom level; interpolate between zoom keyframes with an ease-in-out cubic curve. Default zoom is 1.6x over 700ms.
4. Framing: solid or linear-gradient background, configurable padding, corner radius and drop shadow on the video frame. Presets: 16:9, 1:1, 9:16.
5. Captions: text overlays with start/end time, position, font size, one clean sans font.
6. Preview: canvas-based scrubbing preview at reduced resolution, driven by requestAnimationFrame.
7. Export: POST the project JSON to the server, which builds an ffmpeg filter_complex chain and writes ./exports/NAME.mp4 at 1080p, 30fps, h264, yuv420p. Stream progress back over SSE and show a progress bar.

Out of scope, do not build:
- multi-track audio, music library, transitions beyond hard cuts
- hosted sharing, embeds, view analytics, collaboration
- auto zoom detection from cursor movement
- any login or hosted storage

Requirements:
- Fail loudly at startup if ffmpeg is not on PATH, with the install command in the error.
- No secrets needed, but include .env.example with PORT and MEDIA_DIR anyway.
- README with setup, a worked example project, and a short note on expected render times.
- Type-check clean, no any.

$ open in your agent (prompt prefilled, you press enter) or copy it raw · this prompt is generated from the build plan · improve it via PR

why people still pay

Because the output is public-facing. A demo video is marketing material, and nobody wants to ship a launch clip that looks slightly off because the zoom eased wrong. Paying a small monthly fee to get presets that were tuned by someone who does this all day is a rational trade against an afternoon of tweaking cubic-bezier values, especially when the alternative also means babysitting your own renders.

what you lose

xPreset motion design that actually looks good without fiddling: easing, mouse smoothing, sensible padding

xHosted playback with a share link, embeds and view analytics

xFast cloud rendering instead of pinning your own CPU for ten minutes

xTemplate library and brand kits, so every demo looks like part of a set

xSomeone else keeping up with codec and browser capture quirks

prior art · use these instead of building, if you'd rather

Nothing worth pointing at. That's why the prompt exists.

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