7 Cities is a "tower defense" real-time strategy game, which pits your bristling array of Meso-American towers against a relentless pirate armada and their beastly aquatic allies. You can play the game's survival or seven-level campaign mode (in which you defend seven ever-more-precariously situated cities), and in both you must spend your gold wisely to build defenses around the set path--a river or rivers--upon which your enemies advance.
Similar to other games, you can choose from a variety of towers (such as arrows, cannons, lightning, and even power-boosting Obelisk towers) to take down enemies and boss monsters with varying abilities and vulnerabilities, from heavy-armored battleships to regenerating sea serpents. What sets 7 Cities apart is its leveling system: all towers gain experience and get better with time, and you can upgrade towers endlessly by spending blue gems, another resource that you have to manage as carefully as gold. 7 Cities has an attractive interface, good repeat play value, and excellent production values--in sound, graphics, and game development--making it one the best apps of its kind.