Dragon controller

Act as an expert game developer. I want to build a playable 2D arcade-style web game in HTML, CSS, and JavaScript contained in a single file. 

### Game Requirements:

1. Theme: Player controls a flying dragon navigating through obstacle pipes while dodging enemy knights on bats.

2. Core Mechanics:

   - Dragon flaps/flies upward when pressing the Spacebar, affected by gravity.

   - Fireball Attack: Pressing 'F' shoots a fireball forward to destroy obstacles/enemies.

   - Score increases over time and by destroying enemies.

3. Visuals: 

   - Use clean, modern Canvas drawing (vector shapes or basic colored primitives with glowing fire effects).

   - Dynamic sky background with moving clouds.

4. UI & Flow:

   - Start Screen, Game Over Screen with "Restart" button, and High Score tracker.

Please provide the complete, fully functional single-file code ready to save as index.html and run in a browser.