I absolutely loved this game! I do have a couple of minor gripes with it though.
Gameplay:
First, the walking was rather clunky, often forcing me in a straight line when I attempted to turn. The flashlight running animation played when I just held down shift, even without moving. Turning the flashlight on in general was rather annoying, with it staying pointed down and to the left for around a second or so. This animation could be interrupted though if I very slightly sprint, putting it into the sprinting animation which returns to normal quicker.
The "find the exit" minigame was a bit frustrating, considering the amount of dead-ends, and by the time I became good enough at it to avoid the enemy, it lost its scariness.
The parkour minigame was more frustrating than scary. At one point I got stuck on the side of a ledge where it looked like I could step up it, resulting in me falling off.
Scares:
I didn't encounter all the scares, but here are a couple that I did find ineffective.
As mentioned previously, the "find the exit" minigame lost its scariness after a bit, and playing it twice lets you know what to expect.
I found the losing screen at the end of the parkour minigame to be rather bland. Losing in that style of game in general isn't exactly scary, since you know that you're going to lose. The timer in the parkour minigame also took away the sense of urgency present in the other minigames. I think it would be much more frightening if something was chasing you down the tunnel. Something large would really create a sense of claustrophobia in the confines of the cavern. The thing could even move slightly faster than the player, nearly catching up only to be held back by a particularly small section of tunnel that it must burst through, buying the player some extra time.
With those aside, there are many things this game does fantastically.
Gameplay:
The detailed environments help to really increase the immersion. The audio design is amazing, and the story is intriguing.
I especially enjoyed the "close the doors" and "follow the light" minigames. These were incredibly nerve-wracking, and had me more frightened than any other part of the game. These two were extremely well made.
Scares:
Opening my eyes to see the creature outside the window nearly gave me a heart-attack. The anticipation of not knowing what will be there upon opening my eyes seriously helped to set the mood.
The sense of panic from the "close the doors" and "follow the light" minigames was phenomenal. Forcing me to concentrate and observe what happened around me, before jolting into action set me on edge like nothing else.
I will definitely check out the early access on Steam, and look forward to where you will go from here!