Defend against enemy onslaughts on iOS

My gaming addiction tends to go in phases. Sometimes I like puzzle games, then I'll move on to shooting games. After that, I might switch to racing games or go on to classic arcade. Whatever the flavor of the week is, I like to really get into it to see what the App Store has to offer.

The recent release of a classic iOS game sequel got me back into playing tower defense strategy games. There is something about finding just the right combination of turrets to pass challenging levels that appeals to me right now. After playing the sequel for a bit, I started to check out a few other games. If you like tower defense, this collection is for you.

This week's collection of iOS apps are my favorite tower defense games of the moment. The first has been around for awhile, but continues to be a go-to game when I'm playing tower defense. The second adds unique game elements that change the gameplay by keeping you busy. The third is a sequel to one of the most popular iOS tower defense games of all time.

Kingdom Rush HD ($2.99 - iPad only) is not a new tower defense game, but it's one of my favorites that I continue to play on my iPad. Set in a fantasy world, you'll battle cartoon-like mythical monsters hell-bent on destroying your kingdom. This fixed path tower defense game requires that you choose from four different types of upgradeable buildings with varying damage types to keep the evil fiends at bay. Each level has a set number of available emplacements, so it's important to choose your towers wisely.

Kingdom Rush has a number of settings and maps you'll do battle in and you'll need to experiment to figure out the best strategy for each. You'll first land at a town called Southport, and as you complete each multi-wave level, you'll progress to new locations with different challenges. There are three skill levels to choose from and after each level you'll get a star rating for how well you did. All these variables are what give the game replayability because you'll want to find the best strategy for each skill level.

When I started playing this game, it became clear after only a few levels that using a mix of towers is the best defense against the onslaught of orcs, evil wizards, and trolls. The anchors of your defense are the knights who fight directly on the path and slow down enemies. Slowing their pace is crucial because you'll also want to place archer towers nearby, and the more arrows you can shoot at a slowed enemy, the better. Next you have magical wizard towers that conjure bolts of powerful energy that fry your enemies. Finally, you have artillery towers that offer a slower rate of fire, but very powerful shots. Every one of these towers can be upgraded with gold earned after each kill. Later you can even specialize in a specific type of damage, adding more variety than your original four tower types.

In between levels, you can upgrade various attributes of each tower to make them more powerful, fire faster, and decrease training time for deployable knights. As an extra line of defense you also have two special abilities you can upgrade for when the towers are not quite enough. You can deploy farmers 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 (moreso for the nuke ability) so you'll need to use them sparingly.

Kingdom Rush is one of my favorite tower defense titles to date and continues to be enjoyable every time I fire it up. If you're looking for a tower defense strategy game that's a sure thing, I highly recommend this one.

iBomber Defense Pacific ($2.99 - Universal) has you battling against World War II era soldiers on both land and water as you try to defend your base. You can play through a full single-player campaign, progressing through a huge map with levels at different locations offering unique challenges.

iBomber Defense Pacific offers a number of unique gameplay elements that keep the game interesting. In this game, you'll not only need to worry about placing turrets and blowing away enemies. Sometimes you'll see soldiers come through the trees off the main path as they shoot and damage your turrets. This means that you'll need to also think about the best way to protect your turrets as the attacks keep coming.

You also get secondary objectives beyond surviving every wave of an attack. In one level, you're challenged with bombing several structures. This requires that you first build a bomb factory, then wait for the bombs to be built, then drop them on each of the targets. In another level, you're challenged to blow up crates to open up more space for your turrets. But this means that you'll need to alternate the focus of your turrets to both hitting the crates, then hitting the waves of enemies. More than most tower defense games, iBomber keeps you on your toes.

With beautiful graphics, unique objectives, tons of turrets to choose from, and challenging maps, iBomber Defense Pacific is a must-have for those who want something new from the tower defense genre.

Fieldrunners 2 ($2.99 - iPhone only) is a worthy sequel to one of the earliest and more popular open-field tower defense games to hit the App Store. Using a much more modern setting than Kindom Rush, your job is to stop wave after wave of soldiers, jeeps, and other military units by using turrets to create a maze of destruction. Just like the original Fieldrunners, setting up your turrets in a maze is extremely important because the longer you can keep enemies in front of your turrets, the more likely you'll be able to take down the hardest ones. The game has also added some fixed-path gameplay with trenches you'll need to build around.

In many sequels, I've noticed that developers simply upgrade the art and a few features, but with Fieldrunners 2, it feels like a completely rebuilt game. There are 20 great-looking levels that have you blowing away soldiers in fields of grass, urban landscapes, and sandy deserts. Turrets are more complex than the original as well and change as you upgrade them. The animations for the soldiers also feels much more realistic and fluid.

You get a lot of firepower in Fieldrunners 2. There are 20 unique upgradeable towers to choose from with different types of damage. Everything from machine guns to glue guns (to slow down soldiers) to missile turrets can be used in your death maze. There's even a tower that flings bee hives on soldiers for damage over time. There are also new abilities you can call in like a missile strike or placeable landmines for when things get really tough.

Along with the virtually unlimited ways to create mazes and change your strategy for the game, Fieldrunners 2 now comes with more game types for even more replayability. There's survival, where the waves never end and you simply build and upgrade until the fighting gets too intense; Time Trial, for taking out enemies in the least amount of time; and Puzzle levels that give you other strategic challenges by only giving you certain towers and ways to play.

Overall, Fieldrunners 2 is an excellent tower defense sequel that adds a ton of new content to keep you playing. If you like tower defense -- and specifically, open-field TD -- you will love this game.