mathews-tom/armory/marp-slides

MARP Slides Skill

Author slide decks as plain Markdown using the MARP ecosystem (Marpit + Marp Core + marp-cli) and export to PDF, PowerPoint, or self-contained HTML. Decks are single .md files, git-friendly, and themable with plain CSS.

When This Skill Triggers

• User asks for a MARP deck by name
• User wants "markdown slides" or "slides from markdown"
• User wants a .md file they can commit to git and regenerate deterministically
• User mentions marp-cli, Marpit directives, or asks to theme slides with CSS
• User wants CLI-exportable PDF or PPTX sourced from a text document

When NOT to Use This Skill

Step 0: Gather Requirements

Before generating anything, confirm in a single message. Use defaults silently for anything the user declines to specify — never ask twice.

Step 1: Load References On-Demand

Do NOT read all reference files up front. Based on user intent, load only what is needed. This keeps the skill within armory's token-efficiency budget.

Step 2: Compose the Deck

1. Start with frontmatter. Every deck begins with a YAML front-matter block setting theme, paginate, header, footer, and optionally global style. See DIRECTIVES.md for the full schema.
2. Split slides with `---`. A horizontal rule on its own line creates a new slide. Frontmatter must come before the first slide break.
3. First slide = title. Use <!-- _class: lead --> to center the title slide, and <!-- _paginate: skip --> to hide it from the page count.
4. Middle slides = content. Prefer one idea per slide. If density is dashboard, use metric cards and SVG charts from COMPONENTS.md. If density is minimal, use large headings and whitespace.
5. Last slide = summary/CTA. Mirror the lead class on the closing slide for visual symmetry.
6. Background images use extended syntax: ![bg](url), ![bg left:40%](url), ![bg brightness:0.3 blur:2px](url). Multiple ![bg] tags on one slide arrange horizontally; add vertical for a column layout.

Step 3: Verify Before Handoff

• Frontmatter block present and valid YAML
• theme: matches a known name (built-in or custom in the file's global style: block)
• Every slide break is --- on its own line with blank lines around it
• Relative image paths only (MARP's --allow-local-files requires this for PDF export)
• If using raw HTML (SVG, custom divs), confirm the export command uses --html
• Run the export command once locally to confirm no directive warnings

Step 4: Export

See references/EXPORT.md for the full command reference. Minimal invocation:

npx @marp-team/marp-cli@latest slides.md --pdf --allow-local-files --html

This skill wraps the MIT-licensed MARP ecosystem. See root `ATTRIBUTIONS.md` for upstream credits.

Design Rules

1. One idea per slide. MARP clips overflow silently — there is no warning for content that runs off the bottom.
2. Paginate: skip on title and divider slides. paginate: hold on appendix slides.
3. Relative paths only for images. Absolute paths break in VS Code preview and PDF export.
4. `--html` is required for any SVG, <div>, <details>, or inline styling. Without it, MARP escapes HTML tags to text.
5. Cap lists at 6 rows on content slides. Use details collapsibles or a second slide for more.
6. Headings carry meaning: h1 for slide title, h2 for subtitle, h3 for uppercase section labels. Consistent hierarchy = consistent visual rhythm.
7. Never hardcode theme CSS into every slide. Define it once in the global <!-- style: | --> directive or a separate .css file loaded via theme:.