So so boring
It's a well done game. However, the strategy that gets you the most points is to always shoot at the smallest piece you see, carefully avoiding hitting any of the larger pieces. That way you keep the number of squares on screen as small as possible, greatly reducing your chances of getting hit. Slow and steady wins the race.
The one catch is, this is the most slow and boring thing to do, taking you an extremely long time and a lot of patience.
But it's a well done game and I say good job anyway.