Cellular Automata Simulator (e.g., Game of Life)

Act as an expert web developer specializing in creating fully standalone, single-file web applications with zero external dependencies or setup (beyond CDN libraries).

Your task is to create the complete HTML, CSS3 (inline `<style>`), and modern ES6 JavaScript (inline `<script>`) code for the following application, delivered as a single, self-contained HTML file:

**App Title:** Cellular Automata Simulator (e.g., Game of Life)

**Main Purpose:** Simulate 1D/2D cellular automata.

**Key Features to Implement:**
* Grid display
* Configurable grid/rules
* Step/continuous simulation
* Draw initial state
* Save/load patterns