It was a good series, but throughout the whole episodes you keep thinking, why are they whining so much and accept the tough reality, they still whine even though they became expert fighters. Too much whining to the max.
Ending was horrible, they could have made it much better, just rushed it through and expect us to imagine that they were able to use a weapon (that we have to imagine) that wiped out 99% of the aliens. Great! Let our imagine take place. Also the ending left the teenagers in angst and despair, like another one going mental!
So disappointing how it ended. It was rushed and not much thought went to having a nice ending.