I have now beaten this game on two different occasions. The first time, I got to 90% complete before beating the game, and the second time I 100% it.

The game is very good, but on my first playthrough, I decided I would 100% the game after beating it. However, the impossible lair is exhausting to beat on your first play though. I believe it took me about 18-25 attempts to beat it (can't remember for sure) and this level is well over 10 minutes long. By the time I was done, I didn't want to play anymore. The impossible lair is amazing, but it should really be reserved as the last thing you do in the game. As the final test of skill in the game, it is great and so rewarding when you finally do beat it.

On my second playthrough about a year later, I completed everything before the last level (took about half the time as the first playthrough), and the last level only took me 6 attempts to beat. It was good, and not as exhausting because it was a bit easier for me now. Still difficult though for sure.

I love this game, but just know that when you finish the last level, you are most likely ready to shelve it (for a while at least).