The Kingdom Rush series is a whole lot of Strategy and Tower Defence fun and Frontiers is absolutely no exception. Your goal is to defend the Kingdom against a new enemy in musch the same set-up of the original Kingdom Rush game. The game starts slowly and has plenty of help and tutorials available for new players but anyone with Tower Defence experience will be able to pick up the gameplay in no time.
Kingdom Rush has pre-determined tower locations and a limited arsenal to deploy. The result of this is an incredibly clever gameplay and real strategical skill required to complete the latter stage. Upgrading reinforcements from the beginning is my go-to play for this game.