I really like the game, so I'm going to express my love in my own special way;
HARSH CRITICISM!
The pixel art is good! Everything is nice and pretty. The AA is really nice!
The crystals don't really look glow-y. :S (The fungi do though!)
EDIT: An odd thing I just noticed... in the thumbnail his cloak is red, but in the game it's white... ?
However, some of the art looks off to me... simply because it's shaded.
Some sprites, like the main character, are shaded even though light sources are dynamic, which can look really odd.
Speaking of which, the dynamic lighting blew me away- it's really cool! I loved how the lights changed when doors closed and stuff, it was entertaining to just mess with that for a while!

The music is good! The sound effects really add a lot to the game and I feel a little on edge all of the time because of it.
I feel that in the beginning of the game there isn't reason to really be afraid of the cave other than it being creepy, and that the music should reflect that.
It would also be really cool to have a much more forboding and creepy music play when you approach the bat things... reactive music, you know?
I don't really like the gameplay though.

There isn't a driving mechanic to make me want to play more... if I stand still nothing will happen.
I think it needs to be a bit more active, and have a driving force so you're always moving and doing things.
Spoilers --*
The father's death seems like it should have been a bit more dramatic/traumatic...
There were five seconds of "OH NO HE'S DEAD" *sob* and nothing more really came out of it. :S
Maybe while you're returning to him you should hear him scream?
Being just a bit too late to save your father is much more moving than just finding him dead.
I think perhaps the boy should have had a bit more hatred for the bats? They killed his father, after all.
I'm not saying it's unreasonable to just make the boy scared of them, but it seems like that shouldn't be the only emotion.
The father seemed like a charming fellow, and you did a nice job on that!
I feel (mildly) attached to the father- which is good! You don't know how many games completely fail at character development!
... but perhaps you should have given the player more time to know the father. It's sort of odd to not really care about the father and then have the boy sob about his death... it would help the player feel the boy's pain.
*--
Despite the flaws I still like it.

Favorited!