Seeing that it's based on a manga for boys and rising young popular actors were cast in it, obviously, this movie was targeted at 10s to early 20s. As such, the gore and violence was pretty tame for a Miike movie.
The death games that the high schoolers have to survive are so simple, thus not so interesting, but the opening sequence with the Daruma doll, where gore was replaced with 80,000 red marbles/bouncy balls, was well executed along the theme of child's play succeeding in creating surrealistic imagery and is considered as the highlight of the movie.
The CG was not so bad overall. I like the modeling of the Daruma doll with glaring bloodshot eyes. Also I like the twisted casting for the deadly matreshka dolls dubbed by the voice actors who play Doraemon and Jibanyan, 2 iconic anime characters loved by the nation.
Acting wise, feels like Ryunosuke Kamiki stole the show and the character played by Nao Omori was totally unnecessary.