Kingdom Rush Origins
Tower defense games are so densely populating the App Store now that it's difficult to pick out one that's actually worth your time. That's why Kingdom Rush Origins is actually such an interesting departure and a tower defense title with all its ducks in a row. In short, it's worth trying out!
Like the previous games in the series, Kingdom Rush Origins sets the stage early on for you to appreciate that it's different from its predecessor. It sets out each level with a series of different paths and areas that you can build up your towers. Enemies come marching along ready to attack and it's up to you to keep them at bay. You can upgrade all of your towers in a manner that makes sense to fend off advancing armies, and you can level them up to upgrade them permanently -- that way they'll stay fully powered up. You've also got one hero who can defend your towers as well.
Though this is a new entry in the Kingdom Rush saga, it does little to innovate, even by way of the series it's in. In fact, it's basically the same game you played last time around, albeit there are new enemies and defensive pieces your enemies can put into play to keep you from winning. There's also the usual spread of frustrating IAPs when you need to upgrade right now, which do take some of the fun out of things.
Kingdom Rush Origins is still a very fun tower defense title, even if it's no different from the last game. Or the one before that. It's devoid of innovation, but it's still one tower defense adventure that does what it sets out to do correctly. And in this day and age, that's asking a lot, apparently.