`. Theme values live in CSS custom properties so they are trivial to change. ```html Deck

Deck Title

Subtitle or tagline.

Key points

First point
Second point
Third point

``` ## Viewport fit (hard gate) - Every `.slide` uses `height: 100vh; height: 100dvh; overflow: hidden;`. - All type and spacing scale with `clamp()` — never a fixed pixel font that overflows small screens. - When content does not fit, split it into multiple slides. Never shrink text below readable size and never allow a scrollbar inside a slide. - Avoid invalid CSS such as a negated `-clamp(...)`. Validate at: 1920x1080, 1280x720, 768x1024, 375x667, 667x375. ## Typography and spacing - Strong hierarchy: one dominant heading per slide, supporting text clearly smaller. - Generous whitespace via `clamp()`-based padding and gaps. - A clear visual direction (atmospheric background, accent color) beats a generic template look. ## Accessibility - Semantic structure: `main`, `section`, real `h1`/`h2`, `ul`/`li`. - Readable contrast between `--fg` and `--bg`. - Keyboard-only navigation works (arrows, Page keys, Home/End). - Honor `prefers-reduced-motion` by disabling animation and transitions. ## Content density limits | 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 the viewport | ## Export to PDF (no dependency) The default path uses the browser's built-in Print-to-PDF. Add a print stylesheet so every slide becomes one page. ```css @media print { @page { size: 1280px 720px; margin: 0; } .progress { display: none; } .slide { position: static; display: flex !important; height: 720px; width: 1280px; break-after: page; } } ``` Then: open the deck in a browser, Print (Cmd/Ctrl+P), choose "Save as PDF", set margins to None and background graphics on. Open the deck with the platform opener: macOS `open deck.html`, Linux `xdg-open deck.html`, Windows `start "" deck.html`. Optional, if available: a headless browser (e.g. a Chromium `--print-to-pdf` invocation) can render the same print stylesheet to PDF unattended. Do not require or install it — the browser Print-to-PDF path always works. ## Anti-patterns - Generic gradient decks with no visual identity. - Long bullet walls; code blocks that need scrolling. - Fixed-height content boxes that break on short screens. - Disabling reduced-motion support. - Reaching for a framework or build tool when one HTML file suffices. ## Done when - The deck runs from a local file in any modern browser. - Every slide fits the viewport at all five test sizes with no scrolling. - Arrow/Page/Home/End keyboard navigation works and the progress bar tracks position. - Reduced-motion is respected. - Print-to-PDF produces one page per slide. - File path, slide count, and theme custom properties are explained at handoff.