So I know this doesnt add up, but I will explain.
Story: the story that they had going was AMAZING, I really wanted to see how they were going to get out and what they would find there. Who would survive and would it be a happy ending? I was so excited, then the ending. . . .oh the ending, but that has nothing to do with the story, the story was great the execution was great up until pretty much the very last episode.
Animation: The animation was cool. Lerche did a good job of the animation. It was pretty and did the series justice.
Sound: nothing special, but it was kinda cool.
Characters: I really liked the characters, I just wish that there had been more episodes to learn about them all some more. This would have really added to a series that was pretty good. They all had something unique about them, but we never really got to see any of it come out and be important. This was simply a problem with not having enough room to work with. I feel like Lerche had the capability to make this awesome but did not have the funding it needed to make this a masterpiece.
Overall: The ending was aweful, horrible. They canned the story for some HOPE LOVE AND TRUST WILL ALWAYS WIN EVEN IF THERE IS NO REASON FOR IT. This completely ruined the series for me. It had such great direction and completely screwed itself over. This is one of those animes that did everything right, but then decided to "try to make it something more". This is stupid, I personally think that an anime can be more just be being what it was trying to be. So many animes screw themselves when they flip directions like that. big dissapointment.
this is why this anime has so many high ratings but still gets a 7. I recommend watching it, but the ending ruined the whole build up of the anime. So dont expect an amazing finish.