Motion film for one product idea

The film is code. Every shape, line of text and movement is a Manim animation, and the score is a list of notes in film.json. A re-render gives the same film, frame for frame. No ElevenLabs, no stock music, no footage: the film costs nothing to make again.

For a walkthrough over screenshots, use the training-video skill. For web-style motion and an optional voice, use motion-web-video. This skill is for short films without a voice.

M="${CLAUDE_SKILL_DIR}/scripts/motion.py"

Tools: Manim Community, ffmpeg and ffprobe. The score uses the Python standard library only. On a Mac: brew install ffmpeg and uv tool install manim.

On Windows, install the tools like this:

• winget install --id Gyan.FFmpeg -e and uv tool install manim. Open a new shell, so that ffmpeg is on the PATH.
• Use python, not python3. Use font="Segoe UI", because Windows has no Helvetica Neue.
• To play a draft, use start <dir>\draft.mp4 instead of open.

1. Read the product first

• Read the product's own source of truth: its site, its docs, or the feature plan. Write down the one idea the film shows, in one sentence.
• Every claim on screen must be true today. A feature that is only on dev or only planned is not shown as live.

2. Ask two questions only

Ask with AskUserQuestion, both in one call. Skip any question that the request already answers.

• Visual style: offer 3 film ideas named after the picture, for example "Reach and fence", "Plan as a flow", "Before / after". Give each a one-line description of the scenes.
• Colours: offer the product's own palette first, then 2 others. Give hex values.

Default when nothing is said: 16:9 shape, about 20 seconds, 4 scenes.

3. Plan the scenes

Write the plan in 3–5 lines, one per scene: name, seconds, what moves. A common shape:

1. Wake (3 s): the subject appears.
2. Problem or Reach (5–6 s): what goes wrong, or what it touches.
3. Answer (6–7 s): the product acts on it.
4. Close (3–4 s): product name and tagline, held still at the end for the poster frame.

4. Make the folder and write the scenes

Folder: <scratchpad>/motion-<slug>/. Write scenes.py, one Manim Scene class per scene, and write them one at a time. After each scene, run a draft and look at one frame.

• Set self.camera.background_color in every scene, and use the same colour constants.
• Each scene starts from what the last one left on screen. Re-create that state at the start of the next scene with no animation.
• Use Text(..., font="Helvetica Neue") or the product's font. The default font is a serif.
• No LaTeX (Tex, MathTex): use Text.
• 9:16 and 1:1 trap: Manim keeps the frame width, so a row that fills 16:9 looks small in a tall frame. Stack content vertically and scale it up for 9:16.

5. Write the score in film.json

{"shape": "16:9", "scenes": ["Wake", "Reach", "Fence", "Close"],
 "score": {"master": 0.8, "events": [
   {"type": "pad",  "scene": "Wake",  "at": 0,   "pitches": ["C3", "G3", "E4"], "len": "scene", "gain": 0.1},
   {"type": "hit",  "scene": "Wake",  "at": 0.2, "sound": "whoosh", "gain": 0.4},
   {"type": "note", "scene": "Reach", "at": 0.5, "pitch": "E5", "len": 0.3, "wave": "triangle"},
   {"type": "hit",  "scene": "Fence", "at": 1.2, "sound": "thud", "gain": 0.6}]}}

• scenes sets the order. at is seconds from the start of that scene, so a cue stays on its movement when an earlier scene changes length.
• note: one tone (sine, triangle, square, saw). pad: a soft chord under a scene. hit: a sound effect (thud, pop, tick, whoosh). "len": "scene" lasts to the scene end.
• Put a hit or a note on each thing that lands on screen. Use one pad chord per scene, and keep each scene's chord in one key.
• The mix is normalised to master, so stacked notes never clip.

6. Draft, then final

• Draft (half size, 15 fps, a few seconds): python3 $M <dir> draft → <dir>/draft.mp4. It prints each scene's start and end time.
• Look before you report. Take frames from the middle of each scene and view them: ffmpeg -loglevel error -y -ss <sec> -i <dir>/draft.mp4 -frames:v 1 <dir>/f<sec>.png.
• Check that the sound is in the file: ffmpeg -i <dir>/draft.mp4 -af volumedetect -f null - 2>&1 | grep -E "Audio:|mean_volume". You need an Audio: aac line and a mean volume above about −40 dB.
• Then open <dir>/draft.mp4 so the user can watch it.
• Final, only after the user says the draft is right: python3 $M <dir> final → final.mp4 (full size, 30 fps) and poster.png (taken 1 second before the end).

7. Deliver

• Give the path to final.mp4 and poster.png, the scene plan and the one re-render command.
• Give a list of any on-screen claim you are not sure is true.
• To post it, check that the channel takes video uploads before you write the post.
• To keep it, copy scenes.py and film.json next to the post or the page that uses the film, so that someone can render it again.

Check the script

python3 ${CLAUDE_SKILL_DIR}/scripts/test_motion.py checks the pitch maths, the cue timing, the "len": "scene" length, the master level and that the sound effects come out the same each time.