html-slides

name	html-slides
description	Create zero-dependency, animation-rich HTML presentations from scratch or by converting PowerPoint/PPTX files. Use when the user wants to build a presentation, convert a deck to web, or create slides for a talk/pitch.

HTML Slides

Create zero-dependency, animation-rich HTML presentations that run entirely in the browser.

Inspired by the visual exploration approach showcased in work by zarazhangrui (credit: @zarazhangrui).

When to Activate

• Creating a talk deck, pitch deck, workshop deck, or internal presentation
• Converting .ppt or .pptx slides into an HTML presentation
• Improving an existing HTML presentation's layout, motion, or typography
• Exploring presentation styles with a user who does not know their design preference yet

Non-Negotiables

1. Zero dependencies: default to one self-contained HTML file with inline CSS and JS.
2. Viewport fit is mandatory: every slide must fit inside one viewport with no internal scrolling.
3. Show, don't tell: use visual previews instead of abstract style questionnaires.
4. Distinctive design: avoid generic purple-gradient, Inter-on-white, template-looking decks.
5. Production quality: keep code commented, accessible, responsive, and performant.

Before generating, read STYLE_PRESETS.md for the viewport-safe CSS base, density limits, preset catalog, and CSS gotchas.

Workflow

1. Detect Mode

Choose one path:

• New presentation: user has a topic, notes, or full draft
• PPT conversion: user has .ppt or .pptx
• Enhancement: user already has HTML slides and wants improvements

2. Discover Content

Ask only the minimum needed:

• purpose: pitch, teaching, conference talk, internal update
• length: short (5-10), medium (10-20), long (20+)
• content state: finished copy, rough notes, topic only

If the user has content, ask them to paste it before styling.

3. Discover Style

Default to visual exploration.

If the user already knows the desired preset, skip previews and use it directly.

Otherwise:

1. Ask what feeling the deck should create: impressed, energized, focused, inspired.
2. Generate 3 single-slide preview files in .ecc-design/slide-previews/.
3. Each preview must be self-contained, show typography/color/motion clearly, and stay under roughly 100 lines of slide content.
4. Ask the user which preview to keep or what elements to mix.

Use the preset guide in STYLE_PRESETS.md when mapping mood to style.

4. Build the Presentation

Output either:

• presentation.html
• [presentation-name].html

Use an assets/ folder only when the deck contains extracted or user-supplied images.

Required structure:

• semantic slide sections
• a viewport-safe CSS base from STYLE_PRESETS.md
• CSS custom properties for theme values
• a presentation controller class for keyboard, wheel, and touch navigation
• Intersection Observer for reveal animations
• reduced-motion support

5. Enforce Viewport Fit

Treat this as a hard gate.

Rules:

• every .slide must use height: 100vh; height: 100dvh; overflow: hidden;
• all type and spacing must scale with clamp()
• when content does not fit, split into multiple slides
• never solve overflow by shrinking text below readable sizes
• never allow scrollbars inside a slide

Use the density limits and mandatory CSS block in STYLE_PRESETS.md.

6. Validate

Check the finished deck at these sizes:

• 1920x1080
• 1280x720
• 768x1024
• 375x667
• 667x375

If browser automation is available, use it to verify no slide overflows and that keyboard navigation works.

7. Deliver

At handoff:

• delete temporary preview files unless the user wants to keep them
• open the deck with the platform-appropriate opener when useful
• summarize file path, preset used, slide count, and easy theme customization points

Use the correct opener for the current OS:

• macOS: open file.html
• Linux: xdg-open file.html
• Windows: start "" file.html

PPT / PPTX Conversion

For PowerPoint conversion:

1. Prefer python3 with python-pptx to extract text, images, and notes.
2. If python-pptx is unavailable, ask whether to install it or fall back to a manual/export-based workflow.
3. Preserve slide order, speaker notes, and extracted assets.
4. After extraction, run the same style-selection workflow as a new presentation.

Keep conversion cross-platform. Do not rely on macOS-only tools when Python can do the job.

Implementation Requirements

HTML / CSS

• Use inline CSS and JS unless the user explicitly wants a multi-file project.
• Fonts may come from Google Fonts or Fontshare.
• Prefer atmospheric backgrounds, strong type hierarchy, and a clear visual direction.
• Use abstract shapes, gradients, grids, noise, and geometry rather than illustrations.

JavaScript

Include:

• keyboard navigation
• touch / swipe navigation
• mouse wheel navigation
• progress indicator or slide index
• reveal-on-enter animation triggers

Accessibility

• use semantic structure (main, section, nav)
• keep contrast readable
• support keyboard-only navigation
• respect prefers-reduced-motion

Content Density Limits

Use these maxima unless the user explicitly asks for denser slides and readability still holds:

Slide type	Limit
Title	1 heading + 1 subtitle + optional tagline
Content	1 heading + 4-6 bullets or 2 short paragraphs
Feature grid	6 cards max
Code	8-10 lines max
Quote	1 quote + attribution
Image	1 image constrained by viewport

Anti-Patterns

• generic startup gradients with no visual identity
• system-font decks unless intentionally editorial
• long bullet walls
• code blocks that need scrolling
• fixed-height content boxes that break on short screens
• invalid negated CSS functions like -clamp(...)

Related clarc Skills

• frontend-patterns for component and interaction patterns around the deck
• liquid-glass-design when a presentation intentionally borrows Apple glass aesthetics
• e2e-testing if you need automated browser verification for the final deck

Deliverable Checklist

• presentation runs from a local file in a browser
• every slide fits the viewport without scrolling
• style is distinctive and intentional
• animation is meaningful, not noisy
• reduced motion is respected
• file paths and customization points are explained at handoff

Complete Single-Slide HTML Example

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Slide: API Latency Fix</title>
  <style>
    /* Viewport-safe: fills exactly one screen, no scroll */
    *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

    html, body {
      width: 100vw;
      height: 100vh;
      overflow: hidden;           /* No scroll — this is a slide */
      font-family: system-ui, sans-serif;
    }

    .slide {
      width: 100vw;
      height: 100vh;
      display: grid;
      grid-template-rows: auto 1fr auto;  /* header / content / footer */
      padding: 4vh 5vw;
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    }

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      : center;
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    }

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    API Latency — Before vs After

    
      
        800ms
        Before (SEA users)
      
      →
      
        240ms
        After edge caching
      
    

    
      Engineering All-Hands · March 2026
    
  

Key CSS patterns used:

• overflow: hidden on html/body — prevents any scroll, enforces single-slide
• clamp(min, preferred, max) — scales all text and stats with viewport size
• grid-template-rows: auto 1fr auto — header/footer fixed, content fills middle
• No fixed pixel values — everything relative to vh/vw or clamp()