HTML Presentation Template

Reference architecture for generating slide presentations. Every presentation follows this structure.

Base HTML Structure

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Presentation Title</title>

    <!-- Fonts: use Fontshare or Google Fonts — never system fonts -->
    <link rel="stylesheet" href="https://api.fontshare.com/v2/css?f[]=..." />

    <style>
      /* ===========================================
           CSS CUSTOM PROPERTIES (THEME)
           Change these to change the whole look
           =========================================== */
      :root {
        /* Colors — from chosen style preset */
        --bg-primary: #0a0f1c;
        --bg-secondary: #111827;
        --text-primary: #ffffff;
        --text-secondary: #9ca3af;
        --accent: #00ffcc;
        --accent-glow: rgba(0, 255, 204, 0.3);

        /* Typography — MUST use clamp() */
        --font-display: "Clash Display", sans-serif;
        --font-body: "Satoshi", sans-serif;
        --title-size: clamp(2rem, 6vw, 5rem);
        --subtitle-size: clamp(0.875rem, 2vw, 1.25rem);
        --body-size: clamp(0.75rem, 1.2vw, 1rem);

        /* Spacing — MUST use clamp() */
        --slide-padding: clamp(1.5rem, 4vw, 4rem);
        --content-gap: clamp(1rem, 2vw, 2rem);

        /* Animation */
        --ease-out-expo: cubic-bezier(0.16, 1, 0.3, 1);
        --duration-normal: 0.6s;
      }

      /* ===========================================
           BASE STYLES
           =========================================== */
      * {
        margin: 0;
        padding: 0;
        box-sizing: border-box;
      }

      /* --- PASTE viewport-base.css CONTENTS HERE --- */

      /* ===========================================
           ANIMATIONS
           Trigger via .visible class (added by JS on scroll)
           =========================================== */
      .reveal {
        opacity: 0;
        transform: translateY(30px);
        transition:
          opacity var(--duration-normal) var(--ease-out-expo),
          transform var(--duration-normal) var(--ease-out-expo);
      }

      .slide.visible .reveal {
        opacity: 1;
        transform: translateY(0);
      }

      /* Stagger children for sequential reveal */
      .reveal:nth-child(1) {
        transition-delay: 0.1s;
      }
      .reveal:nth-child(2) {
        transition-delay: 0.2s;
      }
      .reveal:nth-child(3) {
        transition-delay: 0.3s;
      }
      .reveal:nth-child(4) {
        transition-delay: 0.4s;
      }

      /* ... preset-specific styles ... */
    </style>
  </head>
  <body>
    <!-- Optional: Progress bar -->
    <div class="progress-bar"></div>

    <!-- Optional: Navigation dots -->
    <nav class="nav-dots"><!-- Generated by JS --></nav>

    <!-- Slides -->
    <section class="slide title-slide">
      <h1 class="reveal">Presentation Title</h1>
      <p class="reveal">Subtitle or author</p>
    </section>

    <section class="slide">
      <div class="slide-content">
        <h2 class="reveal">Slide Title</h2>
        <p class="reveal">Content...</p>
      </div>
    </section>

    <!-- More slides... -->

    <script>
      /* ===========================================
           SLIDE PRESENTATION CONTROLLER
           =========================================== */
      class SlidePresentation {
        constructor() {
          this.slides = document.querySelectorAll(".slide");
          this.currentSlide = 0;
          this.setupIntersectionObserver();
          this.setupKeyboardNav();
          this.setupTouchNav();
          this.setupProgressBar();
          this.setupNavDots();
        }

        setupIntersectionObserver() {
          // Add .visible class when slides enter viewport
          // Triggers CSS animations efficiently
        }

        setupKeyboardNav() {
          // Arrow keys, Space, Page Up/Down
        }

        setupTouchNav() {
          // Touch/swipe support for mobile
        }

        setupProgressBar() {
          // Update progress bar on scroll
        }

        setupNavDots() {
          // IMPORTANT: Always clear before building — if outerHTML was
          // captured while dots were rendered, re-opening the file would
          // append a duplicate set on top of the existing ones.
          this.navDotsContainer.innerHTML = "";
          // Generate and manage navigation dots
        }
      }

      new SlidePresentation();
    </script>
  </body>
</html>

Required JavaScript Features

Every presentation must include:

SlidePresentation Class — Main controller with:
- Keyboard navigation (arrows, space, page up/down)
- Touch/swipe support
- Mouse wheel navigation
- Progress bar updates
- Navigation dots
Intersection Observer — For scroll-triggered animations:
- Add .visible class when slides enter viewport
- Trigger CSS transitions efficiently
Optional Enhancements (match to chosen style):
- Custom cursor with trail
- Particle system background (canvas)
- Parallax effects
- 3D tilt on hover
- Magnetic buttons
- Counter animations
Inline Editing (only if user opted in during Phase 1 — skip entirely if they said No):
- Edit toggle button (hidden by default, revealed via hover hotzone or E key)
- Auto-save to localStorage
- Export/save file functionality
- See "Inline Editing Implementation" section below

Inline Editing Implementation (Opt-In Only)

If the user chose "No" for inline editing in Phase 1, do NOT generate any edit-related HTML, CSS, or JS.

Do NOT use CSS ~ sibling selector for hover-based show/hide. The CSS-only approach (edit-hotzone:hover ~ .edit-toggle) fails because pointer-events: none on the toggle button breaks the hover chain: user hovers hotzone -> button becomes visible -> mouse moves toward button -> leaves hotzone -> button disappears before click.

Required approach: JS-based hover with 400ms delay timeout.

HTML:

<div class="edit-hotzone"></div>
<button class="edit-toggle" id="editToggle" title="Edit mode (E)">✏️</button>

CSS (visibility controlled by JS classes only):

/* Do NOT use CSS ~ sibling selector for this!
   pointer-events: none breaks the hover chain.
   Must use JS with delay timeout. */
.edit-hotzone {
  position: fixed;
  top: 0;
  left: 0;
  width: 80px;
  height: 80px;
  z-index: 10000;
  cursor: pointer;
}
.edit-toggle {
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s ease;
  z-index: 10001;
}
.edit-toggle.show,
.edit-toggle.active {
  opacity: 1;
  pointer-events: auto;
}

JS (three interaction methods):

// 1. Click handler on the toggle button
document.getElementById("editToggle").addEventListener("click", () => {
  editor.toggleEditMode();
});

// 2. Hotzone hover with 400ms grace period
const hotzone = document.querySelector(".edit-hotzone");
const editToggle = document.getElementById("editToggle");
let hideTimeout = null;

hotzone.addEventListener("mouseenter", () => {
  clearTimeout(hideTimeout);
  editToggle.classList.add("show");
});
hotzone.addEventListener("mouseleave", () => {
  hideTimeout = setTimeout(() => {
    if (!editor.isActive) editToggle.classList.remove("show");
  }, 400);
});
editToggle.addEventListener("mouseenter", () => {
  clearTimeout(hideTimeout);
});
editToggle.addEventListener("mouseleave", () => {
  hideTimeout = setTimeout(() => {
    if (!editor.isActive) editToggle.classList.remove("show");
  }, 400);
});

// 3. Hotzone direct click
hotzone.addEventListener("click", () => {
  editor.toggleEditMode();
});

// 4. Keyboard shortcut (E key, skip when editing text)
document.addEventListener("keydown", (e) => {
  if (
    (e.key === "e" || e.key === "E") &&
    !e.target.getAttribute("contenteditable")
  ) {
    editor.toggleEditMode();
  }
});

CRITICAL: exportFile() must strip edit state before capturing outerHTML.

When the user presses Ctrl+S in edit mode, document.documentElement.outerHTML captures the live DOM — including body.edit-active, contenteditable="true" on every text element, and .active/.show classes on the toggle button and banner. Anyone opening the saved file sees dashed outlines, a checkmark button, and an edit banner, as if permanently stuck in edit mode.

Always implement exportFile() like this:

exportFile() {
    // Temporarily strip edit state so the saved file opens cleanly
    const editableEls = Array.from(document.querySelectorAll('[contenteditable]'));
    editableEls.forEach(el => el.removeAttribute('contenteditable'));
    document.body.classList.remove('edit-active');

    // Also strip UI classes from toggle button and banner
    const editToggle = document.getElementById('editToggle');
    const editBanner = document.querySelector('.edit-banner');
    editToggle?.classList.remove('active', 'show');
    editBanner?.classList.remove('active', 'show');

    const html = '<!DOCTYPE html>\n' + document.documentElement.outerHTML;

    // Restore edit state so the user can keep editing
    document.body.classList.add('edit-active');
    editableEls.forEach(el => el.setAttribute('contenteditable', 'true'));
    editToggle?.classList.add('active');
    editBanner?.classList.add('active');

    const blob = new Blob([html], { type: 'text/html' });
    const a = document.createElement('a');
    a.href = URL.createObjectURL(blob);
    a.download = 'presentation.html';
    a.click();
    URL.revokeObjectURL(a.href);
}

Inline Edit — Enter Key & Paste Fix

When contenteditable is active on elements inside a themed <div> or <section>, pressing Enter inserts a <div> (Chrome default) instead of a <br>, which inherits none of the element's styles and makes the new line appear unstyled. Pasting rich text injects foreign fonts and colors that override the theme.

Add these three guards to every inline-editing implementation:

// 1. Force <br> on Enter instead of <div>
document.execCommand('defaultParagraphSeparator', false, 'br');

// 2. Intercept Enter to prevent the browser default <div> insertion
document.addEventListener('keydown', e => {
    if (e.key === 'Enter' && document.querySelector('[contenteditable]:focus')) {
        e.preventDefault();
        document.execCommand('insertLineBreak');
    }
});

// 3. Strip rich-text formatting on paste — keep plain text only
document.addEventListener('paste', e => {
    const active = document.activeElement;
    if (!active?.isContentEditable) return;
    e.preventDefault();
    const text = e.clipboardData.getData('text/plain');
    document.execCommand('insertText', false, text);
});

Without these fixes: after pressing Enter, new lines render with no theme font or color (issue #49); pasting from a browser or document injects foreign styles that break the theme.

Image Pipeline (Skip If No Images)

If user chose "No images" in Phase 1, skip this entirely. If images were provided, process them before generating HTML.

Dependency: pip install Pillow

Image Processing

from PIL import Image, ImageDraw

# Circular crop (for logos on modern/clean styles)
def crop_circle(input_path, output_path):
    img = Image.open(input_path).convert('RGBA')
    w, h = img.size
    size = min(w, h)
    left, top = (w - size) // 2, (h - size) // 2
    img = img.crop((left, top, left + size, top + size))
    mask = Image.new('L', (size, size), 0)
    ImageDraw.Draw(mask).ellipse([0, 0, size, size], fill=255)
    img.putalpha(mask)
    img.save(output_path, 'PNG')

# Resize (for oversized images that inflate HTML)
def resize_max(input_path, output_path, max_dim=1200):
    img = Image.open(input_path)
    img.thumbnail((max_dim, max_dim), Image.LANCZOS)
    img.save(output_path, quality=85)

Situation	Operation
Square logo on rounded aesthetic	`crop_circle()`
Image > 1MB	`resize_max(max_dim=1200)`
Wrong aspect ratio	Manual crop with `img.crop()`

Save processed images with _processed suffix. Never overwrite originals.

Image Placement

Use direct file paths (not base64) — presentations are viewed locally:

<img src="assets/logo_round.png" alt="Logo" class="slide-image logo" />
<img
  src="assets/screenshot.png"
  alt="Screenshot"
  class="slide-image screenshot"
/>

.slide-image {
  max-width: 100%;
  max-height: min(50vh, 400px);
  object-fit: contain;
  border-radius: 8px;
}
.slide-image.screenshot {
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 12px;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
}
.slide-image.logo {
  max-height: min(30vh, 200px);
}

Adapt border/shadow colors to match the chosen style's accent. Never repeat the same image on multiple slides (except logos on title + closing).

Placement patterns: Logo centered on title slide. Screenshots in two-column layouts with text. Full-bleed images as slide backgrounds with text overlay (use sparingly).

Code Quality

Comments: Every section needs clear comments explaining what it does and how to modify it.

Accessibility:

Semantic HTML (<section>, <nav>, <main>)
Keyboard navigation works fully
ARIA labels where needed
prefers-reduced-motion support (included in viewport-base.css)

File Structure

Single presentations:

presentation.html    # Self-contained, all CSS/JS inline
assets/              # Images only, if any

Multiple presentations in one project:

[name].html
[name]-assets/

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