I liked the puzzles which rely upon boomeranging the projectile backwards to curve your shots. One thing I noticed is in areas where the scrolling stopped, if there is collision at the top of the screen then the boomerang hits it and is destroyed, whereas if there is no object past the edge of the screen the boomerang comes back. But from the player's perspective, both look the same especially on your first time through a level, and so it makes it feel inconsistent whether the boomerang will bounce off the back of the screen or not.
Also, I'm not sure if its meant to look like the boomerang is spinning when its coming back, but it looks like visually there are just two boomerangs, slightly offset, as they return to you. Could be a visual glitch.