/Pretty-mermaid-skills

name: pretty-mermaid
description: |
  Generate and render Mermaid diagrams for architecture docs, READMEs, PRs,
  terminals, chats, and CI as themed SVG, PNG, or ASCII/Unicode art. Use this skill whenever
  the user provides Mermaid code or .mmd files; asks for a flowchart,
  sequence/state/class diagram, ERD, XY chart, or architecture/workflow/data-model
  visualization; or wants to beautify, theme, batch-convert, or make a diagram
  terminal-friendly. Runs locally without a browser or DOM, with 15 built-in
  themes and custom colors.

Pretty Mermaid

Create or render Mermaid diagrams with the bundled Node.js CLI. Use SVG for scalable documentation, PNG for sharing or raster-only consumers, and ASCII or Unicode for terminals and plain text.

Working directory

Treat the directory containing this file as `<skill-root>`. Run bundled scripts from that directory, or invoke them with absolute paths. Keep user source and rendered output in the user's requested location; do not copy the renderer into their project.

Workflow

1. Determine whether the user supplied Mermaid source or needs a diagram authored from prose. 2. Choose the diagram type and output format from the tables below. 3. Read only the relevant reference file when syntax, theme selection, or API behavior needs more detail. 4. Save new source as a `.mmd` file, preserving user terminology and relationships. 5. Render with a named theme or explicit colors. 6. Inspect the result. Fix syntax, clipping, crowded layout, or unclear labels and render again. 7. Return the source and output paths, plus the selected format and theme.

Do not overwrite an existing source or output file unless the user asked for replacement.

Choose a diagram type

| Need | Diagram type | Starter | | --- | --- | --- | | Process, decision tree, architecture | Flowchart | `flowchart LR` | | API calls, messages, interactions | Sequence | `sequenceDiagram` | | Lifecycle or finite-state machine | State | `stateDiagram-v2` | | Classes, modules, relationships | Class | `classDiagram` | | Database entities and cardinality | ER | `erDiagram` | | Bars, lines, trends, comparisons | XY chart | `xychart-beta` |

Read `references/DIAGRAM_TYPES.md` when authoring non-trivial Mermaid syntax.

Choose an output

| Output | Best for | Notes | | --- | --- | --- | | SVG | READMEs, docs, slides, websites | Scalable, themed, supports transparency | | PNG | Chats, previews, raster-only tools | Set `--format png`; no external converter required | | Unicode | Modern terminals and readable text previews | Default ASCII renderer output | | Plain ASCII | Logs and restricted terminals | Add `--use-ascii` | | ANSI-colored text | Interactive terminals | Set `--color-mode` |

Core commands

Run these from `<skill-root>`.

List themes

node scripts/themes.mjs

Render SVG

node scripts/render.mjs \
  --input diagram.mmd \
  --output diagram.svg \
  --theme tokyo-night

Render terminal text

node scripts/render.mjs \
  --input diagram.mmd \
  --output diagram.txt \
  --format ascii \
  --color-mode none

Add `--use-ascii` when Unicode box-drawing characters are not acceptable.

Render PNG

node scripts/render.mjs \
  --input diagram.mmd \
  --output diagram.png \
  --format png \
  --width 1200 \
  --theme tokyo-night

Batch render a directory

node scripts/batch.mjs \
  --input-dir ./diagrams \
  --output-dir ./rendered \
  --format svg \
  --theme github-dark \
  --workers 4

Use batch rendering for three or more diagrams or when consistent options must be applied to a directory.

Theme selection

• General dark documentation: `tokyo-night`
• GitHub dark or light surfaces: `github-dark`, `github-light`
• Print and presentations: `zinc-light`
• High-contrast color: `dracula`
• Cool, restrained palette: `nord`, `nord-light`

Read `references/THEMES.md` or open `docs/THEME_GALLERY.md` when visual theme choice matters. A named theme can be refined with explicit color flags.

Useful options

Shared styling

| Option | Purpose | | --- | --- | | `--theme <name>` | Apply one of the 15 built-in themes | | `--bg`, `--fg` | Set required base colors | | `--line`, `--accent`, `--muted` | Refine connectors, highlights, and secondary text | | `--surface`, `--border` | Refine node fill and stroke | | `--font <name>` | Set the SVG font family |

SVG

| Option | Purpose | | --- | --- | | `--transparent` | Remove the SVG background | | `--padding <n>` | Set canvas padding | | `--node-spacing <n>` | Set horizontal node spacing | | `--layer-spacing <n>` | Set vertical layer spacing | | `--component-spacing <n>` | Separate disconnected components | | `--interactive` | Enable XY chart hover tooltips |

PNG

| Option | Purpose | | --- | --- | | `--width <n>` | Set output width from 100 to 10000 pixels while preserving aspect ratio | | `--transparent` | Preserve a transparent background |

Terminal output

| Option | Purpose | | --- | --- | | `--use-ascii` | Replace Unicode box drawing with plain ASCII | | `--padding-x`, `--padding-y` | Tune diagram spacing | | `--box-border-padding` | Tune padding inside node boxes | | `--color-mode <mode>` | `none`, `auto`, `ansi16`, `ansi256`, `truecolor`, or `html` |

Run `node scripts/render.mjs --help` or `node scripts/batch.mjs --help` for the authoritative CLI list.

Authoring guidance

• Prefer short, concrete labels; preserve domain-specific terms from the user.
• Use explicit edge labels when a branch or message is ambiguous.
• Keep large diagrams readable by splitting unrelated concerns instead of shrinking text.
• Use `LR` for wide flows and `TB` for narrow documents.
• Avoid communicating meaning through color alone.
• Use a light theme for print and confirm contrast against the final background.
• For unfamiliar syntax, start from `assets/example_diagrams/` and consult the diagram reference.

Validation

After rendering:

1. Confirm the