Martian Marine Lander - feedback help

I have released my game - Martian Marine Lander. It has received a couple of mixed reviews. I would like more feedback on it since sales on it have so far been a bit sluggish.

Brief Description
The game is inspired by a classic retro game called Lunar Lander. The object of the game is to conquer the planet Earth by successfully landing a transport ship full of Martian marines in 40 key invasion zone locations.

Demo link
http://www.martianmarinelander.com/Downloads/MartianMarineLander_Demo.zip

Main website
http://www.martianmarinelander.com

Let me know what you think.
Thanks.