Despite of other kdramas which you see lots of good feed backs, you can see tones of negative comments here that I truly think this show doesn’t deserve them!!! The reasons why I believe it in this way are:
You have to watch it till the end to understand everything and for finding out more details you should go back and rewatch it again and again!!! You can understand it lil by lil and the the answers of all the questions are there so there’s no gap or bug!!!
In the other hand it’s sci series and this genre is always confusing which left you with a lot of question marks and answering to all of them is impossible cause the science itself lacks a lot !!! So watching sci-fic movies and series always can be kinda disappointing while it’s reasonable at the same time!
I guess 4.5 completely suits this series and the storyline is so enjoyable and fine but unfortunately you have to be ready for a sad ending:)