These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Surprise Difficulty: Some puzzles look simple, even though they might be quite tough. On the other hand, there is a difficulty ranking system which will give you an idea of how tough a puzzle will be.
The Tetris Effect: You will be thinking in terms of this whenever you see a grid of differently colored shapes. The fact that it has a level editor that requires an understanding of how the puzzles work doesn't help.