Maybe it's just me, but I kind of feel like this game (like a lot of other puzzle games) falls victim to its core puzzle's complexity scaling too quickly for the number of levels you play. The problem isn't that the puzzles get too intricate, too soon, but that they run out of 'twists' in the fundamental mechanics with a sizable chunk of game left. By itself, I don't think this is necessarily a bad thing, but this kind of game usually maintains a steady rise in difficulty from the first level to the last. Which AVNT does... sort of.
Early on, each new level (or set of levels) adds a new, meaningful rule or ability, slowly making the puzzles more complex. At a certain point, it runs out of ways to complicate the puzzles themselves, so it compensates by throwing more enemies at you or giving you less time. In other words, the puzzles stop getting harder, the game just makes it harder to actually implement the solution. This is by far the most apparent in the last level.
Don't get me wrong, overall the game is very enjoyable. And this isn't a problem unique to AVNT by any means. I just don't think I've seen it exemplified so clearly.