Don't waste your time or money!
Like many other reviewers, I found the excessive number of overly long ADs infuriating. Not only are there ADs between levels, but you are forced to watch them in order to get hints, add time, and - most annoyingly- stop and restart a level when you get stuck, which happens quickly as each "easy" level is interspersed with a much more difficult one.
Still, I thought this game would be challenging and enjoyable, so much so that I spent the $4 to "Permanently Remove Ads" - something I almost never do. BUT THE ADS ARE STILL THERE! When I went back to the game "Store", I noticed the AD removel button specifically mentions Pop - Up ADs, so evidently those are the only ones I paid to remove. All the other ADs tied to actual game play are still there.
This is just a major money grab on the part of the developer, which is really sad, because it looks like it could be a quality game. We will never know, however, because I can't imagine many people will have the patience to sit through the hours of AD watching required to make any real progress.