d2

# D2 Diagram Standard D2 remains an installed specialist tool. Mermaid is the default for portable GitHub and Slidev diagrams; use D2 when its composition, styling, boards, or layout control materially improves the result. ## Use D2 When - The repository already owns `.d2` sources. - The diagram needs bespoke composition, nested containers, multiple boards, scenarios, layers, or steps. - A standalone SVG, PNG, PDF, PPTX, GIF, or ASCII export is the primary deliverable. - Mermaid cannot express the visual clearly without renderer-specific workarounds. Use [Mermaid](../mermaid/SKILL.md) for the ordinary case and [LikeC4](https://likec4.dev/) for a durable multi-view architecture model. ## Workflow 1. State the visual thesis, target medium, and expected reading size. 1. Write the smallest readable `.d2` source. Prefer containers, explicit directions, and short labels over manual coordinates. 1. Start with the default `dagre` layout. Try `elk` only when it produces a materially clearer topology; inspect supported engines with `d2 layout`. 1. Use a built-in theme as the base and override its tokens only for brand compliance. Discover current theme IDs with `d2 themes`. 1. Apply the Fmind palette and font guidance from [fmind-theme](../fmind-visuals/references/fmind-theme.md) when appropriate. 1. Format, validate, and render: ```bash d2 fmt diagram.d2 d2 validate diagram.d2 d2 diagram.d2 diagram.svg ``` 1. Trust the command exit status, not only the presence ...