So, I reached "part 5" and got stuck. I was at these two statues with a offscreen plant to the right. I can't get over the wall, neither nearby cannon--one being too high to reach--can hit the second statue, the guy ON the wall can't do anything, and the bubbles can never be guided in way that allows for an easy jump.
The frustration of reviewing a puzzle game is, what does one do if stuck? How does one discuss a game if a single obstacle can hinder progress to the point of urging the player to quit? And what if the solution turns out to be some one-step trick that's only obvious in hindsight?