Problems with this anime :
Scientific Accuracy - It is based on science which is an intresting concept but it isn't mostly accurate. I don't really mind the inaccuracy of the scientific factors but the science explantions are long so the incuarrcy is a bit annoying.
Plot - The main problem with this anime is it's plot, halfway through the series it starts making less and less sense, and you will have so many questions. The story has a great start but the many plot holes it has, just pulls it down. Also the story could have moved in so many ways, but it always takes the most boring direction.
Characters - The character design is very good, but they dont have as intresting personalities as their designs. They are just fine and you don't really relate or feel anything for any character. None of them stands out. Well I think the characers would stand out a bit, if their stories were given a little more screen time.
Good points :
Animation - This anime has a nice, clean style and also very good animation. I don't understand much about animation but this series is visually very pretty.
Sound - It also good soundtrack which adds charm to it's beatiful animation. It just enhances the anime overall.
Last thoughts, this series has so much potential but the plot just sucks big time. If it hadn't for the animation i would have dropped it right after the origin of the village was revealed.