The user wants me to create a Matrix-style digital rain effect. This is a classic visual effect where green characters (typically katakana) fall down the screen in columns, with a trailing fade effect and a brighter leading character.

Let me create a single HTML file with:
1. Full-screen black canvas
2. Green katakana characters falling in columns
3. Trailing fade effect (older characters fade out)
4. Brighter leading character at the front of each column

I'll need to:
- Set up a canvas that fills the screen
- Create an array of columns, each with its own position and speed
- Use katakana characters
- Draw the characters with appropriate colors (brighter at the head, fading behind)
- Clear the canvas with a semi-transparent black to create the trail effect

Let me write this in a single index.html file with inline CSS and JavaScript.

Done! I've created a complete Matrix digital rain effect in a single HTML file. The effect includes:

1. **Full-screen black canvas** - Uses CSS to ensure the canvas fills the viewport
2. **Falling green katakana glyphs** - Uses Japanese katakana characters mixed with some latin letters and numbers
3. **Trailing fade effect** - Achieved by drawing a semi-transparent black rectangle over the canvas each frame (rgba(0,0,0,0.05)), which creates trails as characters fade out
4. **Brighter leading character** - The head of each column is drawn in white/bright green, with the trail fading to darker green

Key features:
- Responsive to window resizing
- Multiple columns with staggered starting positions
- Random speed variations for each column
- Characters change as they fall
- Smooth 30fps animation
- No external dependencies or network requests

The file is completely self-contained with inline CSS in a `<style>` tag and JavaScript in a `<script>` tag.