Firstly, Considering this game is free, I have spent more time playing this, than any other so far.. and that is a credit to the designers... great work guys ! Most other games are completed so quick, leaving you wanting more.. this is still playing after a very long time. I'm currently about half way on second wave, and some of the puzzles have been extremely taxing, I gave up on a couple and moved on to the next, while thinking about the one I was stuck on, and coming back to it with a new idea that popped up in my head, and managing to solve it. I have solved all of them up to now, and really enjoying the experience. What looks so simple, turns out to be much harder than you think. I enjoy puzzles, and this game has been amazing.. easy to play, harder to solve, and really gives your brain a workout, which so they say is good for you. Even though I have played games like Half-Life Alyx, which is breathtaking, the whole thing was over in a few days.. This one is still in play, and with the workshop levels, still growing longer. I have also been working on creating my own puzzle. Designing it was easy, solving it was another matter, it turned out to be incredibly difficult, and has taken over a week, with many hours spent on it. It is now solved, and I have published it to the workshop... look out for the Vulcan Bomber.. looks easy, but it certainly isn't !