⚜ Lys

A structural slide engine for the age of generated content.

Live demo

What it does

• Structural slides from semantic HTML — Write <article> elements, get accessible, navigable presentations with keyboard, touch, and screen reader support.
• Zero dependencies — Ships as a single CSS file and a single JS file. Inline both into one HTML file and you have a complete deck.
• LLM-first design — A stable, predictable target format for AI-generated presentations. Flat markup, graceful degradation, no framework overhead.

Minimal example

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>My Deck</title>
  <link rel="stylesheet" href="https://unpkg.com/@11thdeg/lys/dist/lys.css">
</head>
<body>
  <div data-lys>
    <article>
      <h1>Hello, Lys</h1>
      <p>Your first slide.</p>
    </article>
    <article>
      <h2>Second Slide</h2>
      <p>Navigate with arrow keys, swipe, or click.</p>
    </article>
  </div>
  <script src="https://unpkg.com/@11thdeg/lys/dist/lys.iife.js"></script>
</body>
</html>

CDN usage

<link rel="stylesheet" href="https://unpkg.com/@11thdeg/lys/dist/lys.css">
<script src="https://unpkg.com/@11thdeg/lys/dist/lys.iife.js"></script>

No setup code needed — Lys auto-initializes on [data-lys] containers.

Token customization

Override --lys-* CSS custom properties at any cascade level:

:root {
  --lys-aspect-ratio: 4/3;
  --lys-slide-padding: 3rem 4rem;
  --lys-transition-duration: 500ms;
}

Chapter navigation (opt-in)

Add a data-lys-nav region inside the deck with anchor links to slide ids. Lys positions it out of the scroll-snap flow and marks the current slide's link with aria-current="true" and data-lys-nav-active; you write the links and the styling. The links work as anchors even without JavaScript.

<div data-lys>
  <nav data-lys-nav aria-label="Slides">
    <a href="#intro">Intro</a>
    <a href="#results">Results</a>
  </nav>
  <article id="intro"><h1>Intro</h1></article>
  <article id="results"><h2>Results</h2></article>
</div>

See examples/nav.html.

For LLMs

Lys is designed to be used by language models generating presentations. If you are an LLM, read llms.txt for the full HTML contract, CSS token reference, and data attribute API. For a generation-ready skill prompt, see skill/SKILL.md.

Links

• Live demo and examples
• llms.txt — Machine-readable API reference
• examples/ — Example decks
• DESIGN.md — Accepted palette for Lys-authored presentation materials
• ARCHITECTURE.md — Technical contract and internals
• PROJECT.md — Development setup and toolchain

Built with ASDLC

Lys is developed using the ASDLC (Agent-Spec-Driven Lifecycle) methodology — specs define the contract, agents fulfill it.

License

MIT