Great concept, but there's 2 flaws that I found. The first I found was an accident where I portaled the tractor beam right under the round cube dropper and it got stuck in there, forever. The second is that I was able to bypass the first part of the puzzle pretty easy as soon as I needed the cube by jumping into the tractor beam with the cube and portaled by way to the next part. Fix those 2 and it's a nice little puzzle.