Frontend Slides Skill

Generate browser-based HTML presentations as a single self-contained .html file. Three entry paths: new build from topic/notes, PPTX-to-HTML conversion, or enhancement of an existing HTML deck.

Routing disambiguation: When the user says only "slides" or "deck" without specifying format, ask exactly one question before proceeding: "Should this be an HTML file (opens in browser) or a PowerPoint file (.pptx)?" Route to pptx-generator for PowerPoint/Keynote/Google Slides requests.

Reference Loading Table

Signal	Load These Files	Why
Phase 3 (style selection) or Phase 4 (build)	references/STYLE_PRESETS.md	CSS base block, 12 named presets, mood mapping, density limits, validation breakpoints
SlideController, keyboard nav, touch swipe, wheel scroll, Intersection Observer, reveal animation	references/slide-controller.md	Canonical JS implementation, navigating guard, wheel debounce, IO reveal pattern, anti-patterns with detection commands
PPTX, .pptx, python-pptx, convert slides, extract slides	references/pptx-conversion.md	Safe extraction loop, notes guard, GROUP shape recursion, base64 image embedding, error-fix mappings

Instructions

Phase 1: DETECT

Identify which of the three paths applies:

Path	Signal	Action
New build	User provides topic, outline, or notes -- no existing file	Proceed to Phase 2 to gather content
PPTX conversion	User provides a .pptx file path	Extract with python-pptx; collect slides, notes, and asset order; then proceed to Phase 3
HTML enhancement	User provides an existing .html deck	Read the file; identify what needs improving; skip to Phase 4

GATE 1: Do not proceed without identifying the path. If the input is ambiguous (e.g., "make me a deck" with no file and no topic), ask one question to resolve it.

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Phase 2: DISCOVER CONTENT

Ask exactly three questions -- no more:

1. What is the purpose of this presentation? (e.g., pitch, tutorial, conference talk, internal review)
2. How many slides? (approximate is fine)
3. What is the content state? (bullet points, full prose, raw notes, nothing yet)

Collect or generate the content before touching any style decisions.

GATE 2: Content exists (or the user has confirmed topic-only intent with an explicit "I'll provide content as we go") before Phase 3 begins. Do not start style work with no content direction.

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Phase 3: DISCOVER STYLE

Load skills/frontend-slides/references/STYLE_PRESETS.md now.

Two sub-paths:

Sub-path A -- User names a preset directly: Skip previews. Confirm the preset name exists in STYLE_PRESETS.md. Proceed to Phase 4.

Sub-path B -- User does not know the preset: Ask for mood using exactly these four options: impressed / energized / focused / inspired. Map the mood to candidate presets using the mood table in STYLE_PRESETS.md -- translate the user's mood description to a preset name rather than asking them to choose from a list. Generate 3 single-slide HTML preview files in .design/slide-previews/ -- one per candidate preset -- using real slide content (not placeholder lorem ipsum). Present the previews and ask the user to pick.

GATE 3: User has either named a preset from STYLE_PRESETS.md or selected one of the three previews. A vague direction like "make it look professional" is not sufficient -- a named preset must be confirmed before Phase 4. If no selection is made, regenerate previews with different presets. Never fall back to a generic purple gradient; presets exist to avoid exactly that.

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Phase 4: BUILD

Load skills/frontend-slides/references/STYLE_PRESETS.md if not already loaded.

Build the presentation as a single .html file with all CSS and JS inline (no external CDN dependencies). Follow these rules:

1. CSS base block verbatim: Copy the mandatory CSS base block from STYLE_PRESETS.md exactly as written -- do not paraphrase or rewrite it. Apply the chosen preset's theme variables on top. The base block must be present character-for-character because the validation script checks for it.

2. Viewport fit on every slide: Every .slide element must have height: 100vh; height: 100dvh; overflow: hidden. When content overflows, split the slide into multiple slides -- never shrink text, add scrollbars, or set min-height that could allow growth past 100dvh. A slide with scrollable content is a web page, not a slide.

3. Density limits: Apply the density table from STYLE_PRESETS.md without exception. Maximum 6 bullets per content slide. If content needs a 7th bullet, split into two slides -- dense text is unreadable in presentation context.

4. Responsive sizing: All body text must use clamp() for font sizing. No fixed-height content boxes (height: 300px on inner elements). For images or code blocks that need height constraints, use max-height: min(Xvh, Ypx) with overflow: hidden.

5. CSS negation rule: Never write -clamp(...) -- browsers silently compute it to 0, causing text to disappear. Always write calc(-1 * clamp(...)) when a negative value is needed.

6. JS controller class: Implement SlideController with all of the following (not optional):

   • Keyboard: ArrowRight/ArrowLeft/Space forward; ArrowLeft/Backspace backward; Home/End for first/last
   • Touch/swipe: touchstart/touchend with 50px threshold
   • Wheel: debounced wheel event (150ms) -- without debounce, wheel events cause multi-slide jumps. Add a navigating flag that blocks re-entry during transition.
   • Slide index indicator: currentSlide / totalSlides visible in corner
   • Intersection Observer: add .visible class when slide enters viewport for reveal animations. Use opacity: 0 + transform: translateY(20px) to hide slides before reveal -- never display: none, which prevents Intersection Observer callbacks.

7. Reduced-motion: Include a @media (prefers-reduced-motion: reduce) block that suppresses all transitions and animations.

8. Font loading: Use @font-face with font-display: swap and a system font stack fallback. Never reference external CDN fonts without a local fallback. Missing font-display: swap causes invisible text during load (FOIT).

9. PPTX path: If converting from PPTX, use python-pptx to extract text, notes, and asset paths. Preserve slide notes and maintain asset order. If python-pptx is unavailable, print a clear error and ask the user to install it (pip install python-pptx) or provide content manually -- do not silently skip content.

Optional features (off by default, add only when user requests):

• Speaker notes panel toggled by n key
• @media print CSS for PDF-via-browser export
• Configurable countdown timer overlay

GATE 4: The output HTML file exists on disk and contains the verbatim mandatory CSS base block from STYLE_PRESETS.md. Verify with a string search before proceeding -- a file that "looks right" is not sufficient.

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Phase 5: VALIDATE

Run the deterministic validation script:

python3 skills/frontend-slides/scripts/validate-slides.py path/to/output.html

Exit codes:

• 0 -- All slides pass at all 9 breakpoints. Proceed to Phase 6.
• 1 -- Overflow detected. The script prints which slides overflow at which breakpoints. Fix by splitting the overflowing slides. Re-run validation. Do not proceed until exit code is 0. Content that fits at 1920x1080 but overflows at 375x667 still fails -- clamp() sizing solves most cases; if not, split the slide.
• 2 -- Playwright unavailable. Fall back to the manual checklist gate below. Tell the user validation is running in manual mode and is less reliable.

Manual checklist gate (fallback, only when exit code is 2):

For every slide, verify all of the following. If any item fails, fix it before proceeding.

• height: 100vh and height: 100dvh present on .slide
• overflow: hidden present on .slide
• All body text uses clamp() for font sizing
• No fixed-height content boxes (no height: 300px on inner elements)
• No min-height on .slide that could allow growth past 100dvh
• No -clamp(...) patterns anywhere in CSS

GATE 5: Exit code 0 from the validation script, or -- only if Playwright is unavailable (exit code 2) -- explicit user confirmation that the manual checklist passed for every slide. User confirmation must enumerate the slide count checked.

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Phase 6: DELIVER

1. Delete .design/slide-previews/ unless the user explicitly asked to keep them:

   rm -rf .design/slide-previews/
   

2. Open the file with the OS-appropriate command:

   • macOS: open path/to/output.html
   • Linux: xdg-open path/to/output.html
   • Windows: start path/to/output.html

3. Print a delivery summary:

   File:    path/to/output.html
   Preset:  [preset-name]
   Slides:  [N]
   Theme:   [3 CSS custom properties easiest to change for re-theming]
   

GATE 6: Delivery summary printed. File exists at the stated path. Previews deleted (or user confirmed to keep). Task is complete only when all three conditions are met.

Error Handling

Error	Cause	Resolution
-clamp(...) in CSS	CSS negation of clamp() is silently ignored by browsers -- it computes to 0	Replace every instance with calc(-1 * clamp(...)). Run a grep search for -clamp before delivery.
Font load failure / FOUT	External font CDN unreachable, or @font-face src missing format() hint	Use font-display: swap on every @font-face. Include a system font stack fallback. Test offline.
PPTX extraction error	python-pptx unavailable, or PPTX uses embedded OLE objects	Print a clear error message naming the missing dependency. Ask the user to pip install python-pptx or provide content manually. Do not silently skip slides.
Playwright unavailable (exit 2)	playwright not installed or Chromium browser not available	Fall back to the manual checklist gate in Phase 5. Explicitly tell the user validation is running in manual mode and is less reliable.
Overflow at one breakpoint only	Content fits at 1920x1080 but overflows at 375x667	clamp() sizing solves most cases. If not, split the slide. Never set a smaller viewport as "not important."
Reveal animations not triggering	Intersection Observer threshold too high, or slides hidden with display:none	Use display: flex with opacity: 0 + transform for hidden slides. Never use display: none on slides that need IO callbacks.
JS controller not advancing	wheel event not debounced, causing multi-slide jumps	Enforce 150ms debounce on wheel. Add a navigating flag that blocks re-entry during transition.

References

File	Load At	Contains
skills/frontend-slides/references/STYLE_PRESETS.md	Phase 3 (DISCOVER STYLE) and Phase 4 (BUILD)	Mandatory CSS base block, 12 named presets, mood mapping, animation feel mapping, CSS gotchas, density limits, validation breakpoints
skills/frontend-slides/references/slide-controller.md	Phase 4 (BUILD) — JS controller section	Canonical SlideController implementation, navigating guard, wheel debounce, IO reveal, anti-patterns with grep detection commands
skills/frontend-slides/references/pptx-conversion.md	Phase 1 (DETECT) — PPTX path	Safe python-pptx extraction loop, notes guard, GROUP shape recursion, base64 image embedding, error-fix table