At first, when I saw the spaceship shooting turtle speed bullets, I was thinking "uh-oh", this might be bad. But somehow, after I got the 3-way bullet and then... 9-way... bullet? Things start to get entertaining. The laser and the heavy bomb also have their own use in the right situation. I simply use all my heavy bombs in the asteroid fields as the regular shots (since they drain energy) can't destroy those asteroids fast enough. Same goes with the boss, once it stopped shooting, I simply went in right in front of it and spam everything I got and it goes down very quickly. So the game hooked me back after I had an not positive impression. Great job.
You got all the visuals serviceable, but if you want to kick things up a notch, I recommend having some "impact" visual and audio feedback effects for the regular shots, laser and what not. This is to give the player some gratification of destroying things. Also, you can hype things up, perhaps by moving the background faster when fighting the boss and you know shake the screen a bit.
For the font, it is a bit hard to read. You can use the current font for the title logo or a huge text label, but this font is not suitable for reading.
Other than that, great work. :)