I don't see why getting allies give you special effects instead of actually helping you in battle. You can fight multiple enemies but you can't have others assist in combat?
Why are all the obstacles always perfecly centered on your flight path? Also, why do the birds bounce from side to side? This makes them obnoxious to try to dodge.
I know this is solitare and the cards are supposed to be random...but if there there were cards that were always set in place then at least you could have SOME chance of successfuly finishing a level. Also, I think you should get some kind of currency going for completing levels so players could buy the number cards to use instead of just randomly finding them.
(close to wave 50) Me: ok doing good, no vehicals yet...
2 grenades kill all of my guys except 1, last guy gets gunned down by all my enemies
Me: ok...that was a good game. I think i can do that good again...
wave 12: INCOMING AIRPLANE
Me: shit...