Cool concept! Having only one block and guessing where it needs to be, great idea!
But the game is really hard. While the overall movement is quite good, I had trouble with walljumps. The hitbox from the sprites seems to be a bit larger than the hitbox of the box, and I think I mostly died due to walljumps with spikes directly above the box. Otherwise, I also often died on the box with the goal on it. Making the level all the way, only to have the box disappeare a few frames before you land, aahhhhh, it hurts ;D
But overall I enjoyed it, was something different.