It's not often i find a game i can't win
I play a lot of games. And most of them on hard mode to boot. I decided to try this out since people were whining about how hard it is, only to find they're not joking. The concept is ok, I really liked the music, as even though it never changed it didn't feel repetitive at all. The upgrades are so rare (up till the point i gave up trying) and the enemies keep piling up whether you defeat the last set or not. By the time i got to Paris i was at that point where i wasn't feeling a sense of accomplishment, just a sense of too much effort for too little payout. The difficulty curve is too steep for my taste. I felt like it was easy in the first few missions then suddenly i was struggling just to shoot down one enemy. The Difficulty isn't the issue as much as the reward for survival. For that steep an incline i'd suggest adding a few things to assist, like NPC turrets, or even random bullets from the people on the ground or the healthy buildings. Perhaps making upgrades a little bit more useful, as i saw several levels where i got several upgrades after the weapons i used most that level were maxed, or not enough upgrades dropped leaving enemies nearly impossible to defeat, even with shields. Some people might enjoy retrying a level 20 times working out a strategy to beat it, but to me that get's boring after about the tenth time.