Okay, this is a very good game, so I'm gonna be picky.
The game mechanic is extremely good and original BUT it's also difficult to get used to. I see that you made some arrangements with the difficulty so that the player has some room to mess up, and that's great. But it's still frustrating when you lose and have to start over from the very beginning. What you need here are some checkepoints and a way to skip the (very good) cutscenes.
The throwing mechanic works well, but the little box takes forever to disappear when it falls into space, you need a way to fix that (it adds to the stress, but not in a good way).
I don't understand the purple sticky tiles. Do they do anything different than the "sand" ones? They really look like something dangerous, it's a bit of a problem.
The level design is great. It might lack some direction from time to time, but when I played it I had no problem to get to the end.
The mood is very good too, there's a good sense of mystery, you feel the horror of space in your bones.
I can feel that a lot of effort has been put into the art, but the style is still a bit bland. The texture are a bit boring, some lighting would help, and you should not use so many desaturated colors (all the greys seem to have a 0% saturation value, add some of the ambient color of your game in it)
Well, I guess that's all I have to nitpick. It's really an excellent entry, definitely one of the best of the jam. Great job, please tell me if you make a postjam version! :)