This is the greatest game in the history of Western Civilization. Challenging, tricky, rewarding, satisfying. Requires skill, speed, patience. And quirky enough to try at that patience and frustrate you. The perfect game! No advancing to another level. Each puzzle stands on its own. You can navigate in the menu by jumping around, going forward or backward, to attempt a new puzzle independent of which one you just played. Graphic design is colorful and imaginative. And it does take up too much core! No continual appeals to upgrade in any way is definitely a plus and the attendant ads are amusing. It's right up there with Tetris with being intoxicating, easy to play, and ubiquitous and universal because it can be played all over the world without language translation limitations.
Kudos to your software engineers.