Just finished all 121 levels. A truly excellent puzzle game. While the visual presentation isn't all that striking at a first glance, it allows for an amazing level of overview of each puzzle. The mechanics that are employed are also masterfully executed, each new one including a new element that combines with all others. And while some of them can be frustrating in certain puzzles I don't think I found any one mechanic that I outright disliked per se as opposed to just in certain puzzles. A truly remarkable game.