Loved the goblin characters they were so cute! I really enjoyed the audio aspect, I think the way the player can utilise the audio to identify where the goblins are is very unique and I haven't really experienced something like that before!
I would say that maybe more indication on where the goblins were could of helped, I don't know if it was just chance or design, where the last goblin felt so hard to find, I wasn't a big fan of that, I thought as though it just got a lot more difficult and I just wanted to progress.
I think a cool idea would be utilising the firefly effect, to highlight a broad area of where the goblin is or just a random point near the goblin, sometimes this felt like it was the case, although that could of just been luck.
The upgrade system felt really rewarding, I almost always went with the hearing upgrade, since that part of the game I enjoyed most. I think it was a bit too easy when it came to the torch dying out. Maybe you could of limited the amount of campfire use, so that the campfire dies down as you refill the torch.
You were spot on with the themes, with the hidden goblins and the free choice of upgrades. Overall this was really fun to play!