Fun, simple game.
I admit that I was surprised that I enjoyed the game as much as I did. I played it a few times. I think something that you excelled at with the game was minimizing the "punishment" for losing, which made it easy to want to try again.
The controls were on and the graphics and sound worked really well together. Adding additional planes was a nice touch for difficulty.
I would've like to have hit the paratroopers from the sky for bonus points. Also, starting the game initially with Spacebar was unresponsive for some reason. I had to hit the spacebar a few times to get it to work.
In any case, nice work.