Hi metal buddy :)
I finally tested your demo, and loved the concept of revealing hidden things :3 I also love the art and the atmosphere you put in place (in normal time i'm not a fan of Limbo like games, but you achieved to create your own gameplay and visual and that's cool ^^ ).
Maybe a little audio feedback from the firefly would be welcome when there is something, I had some troubles during the the hedgehog riddle ^^" And maybe a reminder when comes the first time to drag a box (I didn't remember at the first time the key, it wasn't an actual problem, but it would be nicer to learn the mechanics this way, like when we fall and press Z )
Anyway, great job ! I'll stay tuned on your progress :)