Hmm...

Cons:
No sound.
No instructions.
Limited control - up, down, and shoot only.
Very repetitive.

Pros:
Um...you shoot stuff. That's about it.

Ahh!

How do you shoot???

Seriously buggy...

I started on "Easy", got killed. Then clicked "legendary", and it seemed no more difficult than Easy... once I died I clicked the "fun" in the corner, died again and clicked Legendary one more time. This time there was a constant stream of like 50 of the enemy swarming across the screen. I couldn't even fly down into them to get a shot off, they were so dense. But I did find that if I clicked in the swarming mass of enemies that any click that landed on an enemy gave me 100 points for no good reason. And also, when I died, it was extremely difficult to click the "again" text through all of the baddies... but once I did, on the intro-screen to start the enemies were still swarming across the screen. So yeah... this is very, very buggy, and needs to be fixed, put in sound, more levels, power-ups, variety, etc.