I have not played the mobile game before, and as a result this is a review from an anime only.
This "movie" is a short one lasting for less than half an hour. The plot is hard to follow since it seemed like the staff animated the most important scenes and cut the rest of the story making the whole movie less cohesive. As a result don't expect any real character development or feel any strong bond towards any of them.
The art is well done however as expected of production I.G the action scenes in particular were fun
The music itself didn't feel out of place with the scenes but was not something extrodinary. The ending song was well chosen but not notably good enough to not skip.