A decent space invaders clone. Going to second Gumball's comment on the movement... as I recall one of the key strategies in Space Invaders was trimming invaders off the sides to slow down how quickly they advance. I also think there was a greater limit on the number of shots in flight, so there was much more incentive to not miss, otherwise you had to wait for your next shot. In your game I could just hold down shoot and move around dodging incoming fire, so it was more about dodging than shooting.

The special attack was an awesome surprise - really liked that!

Here's my scores:

Nice space invaders clone, but the enemies move oddly.  When an entire column on the left or right is destroyed the rest of the enemies should move all the way to the edge of the screen.  The game instead acts like the column is still there.  This makes the enemies drop much quicker than in the original game.