ill start with the negatives, because they are very few
it starts really slow. the first 5 episodes are confusing and the rest 10 episodes are slow. bbut then the epic emotional journey begins.
STORY 10 / 10 : the story is simple and confusing at the same time. what i mean is, they took a simple overused theme/story such as time travelling but they put many theories by real life existed scientists and they combined them and made a rather magnifisent theory using the butterfly effect to bring in the "drama" part of the anime.
ART 8 / 10 : the art style is unique, its really good, nothing too exciting, the animation is great and simple.
SOUND 9 / 10 : there arent many soundtracks but the 2 main ones (gate of steiner and believe me) are amazing outstanding overplayed ones. the ending song tho is magnificent
CHARACTERS 9 / 10 : likable, UNIQUE, developed the way they sould be
ENJOYMENT 8 / 10 : at first boring but then i loved it (i even teared up a little :P )
VOICE ACTING 10 / 10 : AMAZING!!!!
OVERALL : 9 / 10