Yes, I agree on the trial and error for the last level in particular. It was a bit of a troll level to push the tech to the limit. The only hint is to look for the background changes - there are four different backgrounds and one key in each background. But still, quite impossible and not fun, honestly.
For the other levels, I perceive the trial and error as exploration. Just like exploring a normal level in a 2d or 3d game, which is fun to do, you also need to explore these levels... but since the space is non-euclidean, you have to think out of the box to fully explore everything.