The movie is a good movie, with a plot that builds fairly well, and with many standard horror-movie ingredients. The main characters play well enough too.
I still hold back on the scoring, because the movie didn't give me enough back for the unpleasantness it presents.
One standard element for horror it uses is playing mind games on the characters - this works (maybe too?) well, especially in the first half of the movie. It also uses graphic and sudden gore, this also adds to the unpleasant feeling. Another standard element is isolation, and the element of being trapped.
Of course, a Horror/Sci-fi is not supposed to be pleasant, but you should have another feeling than just "I am glad the movie is over".
I still hold back on the scoring, because the movie didn't give me enough back for the unpleasantness it presents.
One standard element for horror it uses is playing mind games on the characters - this works (maybe too?) well, especially in the first half of the movie. It also uses graphic and sudden gore, this also adds to the unpleasant feeling. Another standard element is isolation, and the element of being trapped.
Of course, a Horror/Sci-fi is not supposed to be pleasant, but you should have another feeling than just "I am glad the movie is over".