This is solely my opinion:
Theme: There is not much exploration to do as the path is straight forward. I understand we are in darkness but the only thing referencing to discovery is the rocket to see the monsters. And even that gets progressively removed. Therefore can't give it more than 3 stars.
Fun: It was super fun to play and I really enjoyed the overall experience. Specially fighting the enemies and moving around. 5 stars.
Controls: They are tight and good but the portal has some immortality glitches and enemies seem to have more life in darkness than revealed. I needed three-four shots to take them down on dark and one shot on light. 4 stars.
Sound: There is no soundtrack therefore can't give it much thoughts. Although this game reminds me of FNAF mini-games. Therefore it might not need it. Anyway SFX is cool for the style but the soundtrack lack removes some charm. Therefore 3 stars.
Originality: It's something I haven't seen before in games but I do see one or two mini-games of this. Therefore excluding exceptions, I give it 5 stars.