It was very hard for us to get into the game which plays into a chemistry laboratory. The goal is to free an experimental animal. In the beginning we had no clue what to do and without a hint we would probably still sitting in the anteroom. But after that the flow was fine.
There were a couple of challenging self made puzzles which fit into the setting. If you need extra time at the end, you can buy it. I think 10€ for another 10 or 15 minutes. We didn’t need it. A team size of 2-4 players is fine.