The user wants me to build a top-down alien shooter game using Phaser.js. Let me plan out the requirements:

1. Use phaser.min.js that's already in the current directory
2. Single HTML file (index.html) with CSS in <style> tag and JS in <script> tag
3. No external resources - everything must be self-contained
4. Game features:
   - WASD movement
   - Aim and fire at advancing aliens
   - Health system
   - Score system
   - Increasing difficulty (waves get harder)

5. Procedural graphics - use Phaser's drawing methods (graphics, shapes, etc.)
6. No external images or audio files

Let me create a complete game:

Key game mechanics:
- Player: Top-down view, WASD to move, mouse to aim, click to shoot
- Enemies: Aliens advancing from top of screen towards player
- Health: Player has HP, take damage from aliens reaching player or touching them
- Score: Points for killing aliens
- Difficulty: Increase enemy spawn rate or speed with each wave
- Waves: End when all aliens are defeated, start next wave with more/stronger enemies

Procedural graphics:
- Player: Draw as a shape (triangle/rocket)
- Aliens: Draw as aliens with greenish color
- Bullets: Small circles or lines
- Background: Dark color with procedural stars

Let me write this game:

I've created a complete top-down alien shooter game using Phaser.js. Let me verify it has all the required features:

1. ✓ Single self-contained HTML file with CSS in <style> tag and JS in <script> tag
2. ✓ Uses phaser.min.js from the current directory
3. ✓ No external resources or network requests
4. ✓ WASD movement
5. ✓ Mouse aiming
6. ✓ Shooting at advancing aliens
7. ✓ Health system
8. ✓ Score system
9. ✓ Increasing difficulty (waves get harder)
10. ✓ Procedurally generated graphics (player ship, aliens, bullets, explosions, stars)

The game includes:
- Player controlled by WASD keys, aiming with mouse, shooting with click
- Wave-based enemy spawning with increasing difficulty (more enemies, faster, tougher)
- Health system that decreases when aliens touch the player
- Score tracking
- Wave counter
- Game over screen with final score
- Start screen with instructions
- Procedural graphics for all game elements (no external images)
- Particle effects for explosions and hits
- Engine glow effect when moving
- Starfield background with parallax-like movement
- Grid pattern for visualreference