Editors' note: This review has been updated with new levels and features added in version 1.2.
Kingdom Rush Frontiers (iPhone|iPad) is the sequel to hit tower defense game Kingdom Rush, keeping the same great gameplay with fun improvements and extras. The latest update adds even more to like, including new stages, enemies, and a challenging boss fight.
Just like the original, Kingdom Rush Frontiers is set in a fantasy world where you'll battle cartoon-like mythical monsters hell-bent on destroying your kingdom. As a fixed-path tower defense game, you'll be required to choose from four different types of upgradable buildings with varying damage types to keep the evil invaders at bay. Each level has a set number of available emplacements, so it's important to choose your towers wisely.
In between levels, you can upgrade various attributes of each tower to make them more powerful, fire faster, and decrease training time for deployable units. As an extra line of defense you also have three special abilities you can upgrade (that you'll unlock as you play) for when the towers are not quite enough. You can deploy units on the ground to back up your knights or you have a "nuking" ability for emergencies (like a flaming meteor). Both have a cool-down time (more so for the nuke ability) so you'll need to pick the best time to use them. Your third instant special ability is yours to choose, by buying items in the in-game store. Each stage you'll earn a number of gems that can be used to purchase items in between stages. I've had some luck using an ability that lets you drop a potion to freeze enemies for a short time, but, if you have the gems, there's even a "Fat Boy" nuclear weapon that clears the map.
Another cool element of the game is the ability to use and upgrade a hero; a single named unit with special abilities that you can direct to any area of the battlefield. The hero comes in handy in particularly difficult battles, and you'll have three different types that unlock as you play. Kingdom Rush Frontiers (like the original) also has several heroes you can unlock for up to $6.99 in real money, but the three you get simply from playing are quite powerful on their own.