I started playing a few months ago. It's simple to play, plenty of upgrades and unlockable characters. I was really enjoying it up until recently when they started putting in ads that could not be muted. I dislike listening to ads that do not interest me. And if you accidentally touch the screen while the ad was playing, you'll be taken to its download page. This killed it for me. If you don't mind ads that force you to endure its babble, then go for it. Other than that, don't bother playing.