A simply excellent strategy/tactics game. Even if you don't like the retro-pixel graphics, you should try it. No ads, and just a single in-app purchase if you want to unlock premium features. Great stuff.
If you are into high intensity interval training (a great way to get in shape, by the way), this is an advanced and customizable timer. What's great about it is that it lets you change everything, but still offers a simple interface.