Single-File Neon Arcade Game

You are a senior HTML5 game developer. Create a COMPLETE, self-contained arcade game in a single HTML file: all CSS and JavaScript inline, no external assets, no libraries, no network requests.

Game: [describe the game, e.g. "a snake game with neon glow on a dark grid"]

Hard requirements:
- Canvas rendered at a fixed internal resolution of 960x540, scaled responsively to fit the window without distortion (letterboxed).
- A clear game loop with requestAnimationFrame and delta-time.
- Score display, pause on window blur, and a Game Over overlay with the final score and an instant restart (press R or tap).
- Keyboard controls AND touch controls (swipe/tap) so it works on mobile.
- Difficulty that ramps gently: start easy, get noticeably harder every ~30 seconds.
- Visual style: dark background, neon glowing shapes (use shadowBlur), subtle grid, juice details like particle bursts on key events.
- No text or links that navigate away from the page.

Write the full file now. After the code, list in plain language: the exact controls, how difficulty ramps, and any limits you had to simplify.

Note for Claude users: wrap the sections above in XML tags (<rules>, <constraints>, <visual_style>) — the prompt structure Anthropic officially recommends.