I love these types of games, but all too often they’re just level after level of simple puzzles, with no real challenge. This is a surprising exception. The levels do get progressively more difficult, and many of them require some real thought and consideration to solve.Where it needs work: Sadly, the game does drain my battery quickly; I only play more than 1 or 2 levels if I’m charging my phone; it also seems to overheat my phone . If this proves to be a long-term problem, I may decide to ditch the game, but I hope not.I’ve seen other reviews mention having to watch a full ad after every level, but I’m not experiencing that. An ad after every level, yes, but all of them have a close option after 5 seconds or so. BUT some of the ads do “glitch” when you try to close them; it shows the x to close, but when I tap it, it takes me to the download page, sometimes several times in a row on the same ad. I realize this is not a problem with the game, but with the ad itself. And it’s maybe one ad in 20 that does this. All in all, worth the download at least.