Chat Stack

---
name: mb-chat-stack
description: Plain cut-paper chat bubbles arrive and stack up, each after a moment of typing dots, then the last one expands to fill the frame with the payoff. Use it to act out an objection and its answer. Renders one 1920x1080 30 fps H.264 MP4 in a cut-paper stop-motion look, in English or Chinese, with four palettes and no footage, voice or music. Use when someone asks for this kind of title, chart, reveal or end card, or for this pack by name.
version: 1.0.0
---

# Chat Stack

Plain cut-paper chat bubbles arrive and stack up, each after a moment of typing dots, then the last one expands to fill the frame with the payoff. Use it to act out an objection and its answer.

Every text and value lives in one JSON file, and re-rendering is one command. The look lives in `assets/`. Your job is to fill the fields, never to restyle. Exact tokens and timings are in `references/style.md`.

## Inputs to ask for

Ask once, in one message, for what the brief does not give:

1. 2 to 6 short messages and one payoff line.
2. The user's own text or facts. Paste them unchanged into `"source"`.
3. Language: `en` or `zh`. One language per version; for both, make two JSON files.
4. Palette: `vermilion`, `cobalt`, `pine` or `apricot`. If nobody says, use apricot.

**No answer comes:** proceed, and list your assumptions at the top of your reply.

## Steps

1. Write `clip/beats.json` in a new folder. `assets/library.json` and `assets/library.zh.json` are valid filled examples: copy the shape, not the fictional words.
2. Validate: `node <skill>/scripts/check.mjs clip/beats.json`. Fix everything it reports.
3. Look before rendering: `node <skill>/scripts/sheet.mjs clip/beats.json clip/sheet.png --at 0.99`, then view the image. Try `--at 0.5` as well.
4. Render: `node <skill>/scripts/render.mjs clip/beats.json --out clip --flat`.
5. Check what a viewer sees: `node <skill>/scripts/check.mjs clip`. Fix the JSON, re-render, and check again until it passes.
6. Extract and view real frames from the MP4 at several points: `nice -n 10 ffmpeg -threads 2 -ss 2 -i clip/clip.mp4 -frames:v 1 f.png`. The checker cannot judge whether it looks right. You can.

`--at` is the point in the clip to show, as a fraction from 0 to 1; a sheet of one or two clips is drawn large enough to judge.

Options: `--only clip --frame 120` re-renders one frame to `clip/frames/clip-120.png`. `--stills 0.3,0.6,1` writes stills to `clip/frames/`. `--scale 0.5` makes a draft at `clip/draft/clip.mp4`, even with `--flat`, and the checker refuses drafts. Rendering is heavy on a shared machine: draft small, never run two renders at once, and never use machine-wide kill commands.

`check.mjs` runs from wherever the skill is installed. Give it a JSON file, a folder (with `--beats path/to/beats.json` if the JSON is elsewhere) or any MP4. To run every check on a renamed MP4, add `--beats`. `check.mjs --test` is a short self test. It catches: overflow, stranded words, low contrast, frozen clips, an empty payoff, wrong size or codec, and placeholders.

## beats.json

```json
{
 "lang": "en",
 "palette": "apricot",
 "label": "Fictional example",
 "source": "Fictional example: a bakery chat.",
 "beats": [
  {
   "id": "clip",
   "job": "statement",
   "effect": "chat-stack",
   "seconds": 8,
   "slots": {
    "messages": [
     {
      "text": "Do you have any rye left?"
     },
     {
      "text": "We sold out by nine."
     },
     {
      "text": "Again?"
     },
     {
      "text": "Every Tuesday, this fictional month."
     }
    ],
    "payoff": "Order by noon the day before."
   }
  }
 ]
}
```

| Field | Meaning | Limit | Thin brief |
|---|---|---|---|
| `lang` | Language of all text on screen | `en` or `zh` | Use the language of the source |
| `palette` | The one colour setting | One of the four | apricot |
| `label` | Small tag on the clip | 30 characters, optional | Fictional example for samples, or 虚构示例. Leave it out for real work |
| `source` | The user's text, unchanged. Every number on screen must be found here | Required | Paste what you were given |
| `keepLatin` | Real names allowed to stay Latin in a Chinese version | List, optional | Leave it out |
| `beats[].id` | Clip file name | Letters, digits, hyphen | clip |
| `beats[].job` | Keep as shown | `statement` | `statement` |
| `beats[].effect` | Keep as shown | `chat-stack` | `chat-stack` |
| `beats[].seconds` | Clip length | 5 to 9 | 8 |

## Every field in slots

| Field | Meaning | Limit (characters) | Thin brief |
|---|---|---|---|
| `messages.text` | One chat message, as written in the script. | 60, required | Use lines from the script. Never compose a real person saying something. |
| `messages.side` | left or right. Default alternates. | left/right, optional | Leave it out. |
| `messages` | List (2 to 6 items) | | |
| `payoff` | The line the clip ends on, in large type. Required. | 60, required | Use the strongest line in the script, unchanged. |

## Rules

**The look is original and neutral:** it does not imitate any real chat product, and must not be restyled to. **Messages:** use lines from the script. Never compose words for a real person.

**Generate no invented numbers.** Every figure must be in `source`, and the checker fails any that is not. **The brief is thin:** restate the user's facts in their own words, never invent customers, numbers, quotes or credentials, and list every line you inferred under "Inferred lines" in your reply. **Nobody can answer:** proceed and list your assumptions. **Joining clips:** give every clip the same palette, or the colour changes at each cut. **A different length is wanted:** change `seconds` within the range. **No real link:** do not show an address. **Line breaks:** words are kept whole; if a break reads badly, put `\n` in the text.

## Deliverables

`clip/beats.json`, the one file to edit, and `clip/clip.mp4`: 1920x1080, 30 fps, H.264, yuv420p, silent. Add a note with assumptions, inferred lines and the re-render command.

## Render time

Measured on a 16 GB Mac with other work running, at low priority and full size: 6 s for this 8-second clip with its default material.

## Before delivering

- [ ] `check.mjs` on the folder exits 0. Quote its last line.
- [ ] You viewed real frames from the final MP4 at several points.
- [ ] Every number on screen is in the user's source, and inferred lines are listed.
- [ ] One language per version.
- [ ] Fictional material is labelled through `label`.
- [ ] No footage, voice or music was generated.

## When not to use it

The conversation is a real one you need to show as evidence: use a real screenshot in another pack. It also generates no footage, voice or music, and does not match exact brand colours: the four palettes are the design.

## Requirements

- Node 18 or later, and ffmpeg with ffprobe on the PATH or in /opt/homebrew/bin.
- Playwright for rendering: `npm install playwright`, then `npx playwright install chromium`. If it is installed elsewhere, set `NODE_PATH` to that `node_modules`. `check.mjs` needs no packages.
- Fonts are system stacks. Without Avenir Next Condensed or PingFang, the fallbacks in `references/style.md` apply and the text is re-fitted. Run the check there.