First of all I'd like to say that I'm a huge fan of Science;Adventure franchise. I am familiar with nearly every entry in the series in every medium, be it visual novels, anime, manga, Drama CD, or light novels, etc. Now, I'm not saying this as justification of why you should pay attention to this review or how it is substantial or whatnot. The reason why I'm telling this is because I want reader of this review to understand how important the series is to me, how am I in love with it, so I'm ready to dedicate enormous amount of time to it. Yes, you can call me a fanboy, this would be complete truth.
And this is important for reader of this review to know because of what I'm going to say about the movie in subject. It's awful.
And of course, I am going to explain why it is awful.
The main reason behind this movie being a failure is it's far-fetched story, which contradicts all canon established before, which violates main rules of the setting.
I assume that you are already aware of what's going on in the movie.
It's basically "The Disappearance of Okabe Rintarou". After a year from the events of the original visual novel and anime series, Okabe Rintarou and everyone else are leading a normal everyday life, but one day Okabe just disappears in broad daylight and nobody remembers him. Except there is a barely perceptible feeling inside Kurisu that something is missing.
So far up to this point in the story, everything was pretty alright, if you forget about how fast pacing is or how poorly characters interact. Well, it's not completely as bad as I'm painting it. The movie tries really hard to appeal to watchers, tries to create funny situations and make characters interact like in the original, but poor time management makes it less believable. Even if that's so, movie is still very cute and enjoyable to some degree.
But from the point where you learn the real reason of Okabe's disappearance, it all goes straight to hell.
Because the real reason, as I said before, contradicts main rules established in story. There're basically two main interpretations of ongoing events. The one of this interpretations actually makes sense and from its point of view, no rules were violated. Except this interpretation builds upon assumption that everything characters are saying is incorrect or a lie.
And that can't be the case, the reason is very simple: this is not how storybuilding works.
If the writers really knew what they were doing, they would have planted a correct explanation to the story unless there is a significant reason for the plot to not to have the correct explanation. Which isn't like that in this movie, because such method only makes plot to be nonsensical. More to that, if we start to assume that everything characters said in the movie may be incorrect, why won't we go further in our assumptions and say that every other rule established in the original might be incorrect, since we have no solid proof that anything said in the original is truth.
And the other interpretation doesn't even need to be analysed to make no sense, you just have to keep in mind what Suzuha said about world lines in the series.
And because of how story has such significant plot holes I couldn't enjoy it at all. It had couple of great scenes, though. For example scene on the train station where Okabe and Kurisu were talking, mimicking Houoin Kyouma, the ending... and... and... well, that's it.
The other significant flaw of the movie are characters. Yup, you didn't misread it. That god-tier character cast which the original had are turned into something... I don't even know. Maybe the reason is that the movie had only 90 minutes, which clearly isn't enough to reveal characters. Maybe the problem is that there isn't anything new in their interactions, because basically 90% of all "good" (not really good) moments are a copypaste from the original.
The movie tries too hard to pander to the audience through pure fanservice, forgetting about everything else like plot or characters.
And yeah, well, it's pretty enjoyable fanservice-wise. So, if you really are able to not think while watching the movie and enjoy just how camera angle showing Kurisu's flat chest or how tearjerking forced drama moments are... well, you may even like this.
