Tower defense games are generally low-resource titles that are heavy on challenge. They were among the first titles to be ported from browsers to smartphones once the App Store took off, so there's been more than enough time to build up a nice stash of recommendations.
If you enjoy combining strategy and brute force, or if you were just the kind of kid that enjoyed lobbing water balloons at teachers from three storeys above, hit up the App Store and get involved in these tiny wars.
Castle Doombad ($2.99)Get it here
Adult Swim Games' Castle Doombad mixes up the tried-and-true tower defense formula in a couple of ways. For starters, it opts for a multi-tiered side-on view as opposed to a traditional top-down view. Also, the game isn't about heroes defending their home from an encroaching evil. Rather, it's about a bad guy employing traps and servants to keep his kidnapped princess locked up and far away from meddling heroes.
Castle Doombad is good fun. The game really subscribes to the whole "tower" part of "tower defense," as the do-gooders employ ladders just as often as they try to sneak in from the ground floor. Best of all, some of the heroes ride fat ponies that look like they came from that Bugs Bunny opera cartoon.
Plants vs Zombies ($0.99 USD)Get it here
Don't be fooled: These damned undead won't stop once they've devoured your garden. Those smiling sunflowers are just a salad appetizer. They want your brains, and if your plants (and your last-ditch lawnmowers) can't stop them, nothing will.
Plants vs Zombies' wry sense of humor has helped propel it into popular culture as much as its addictive and increasingly-intense gameplay. This is one enjoyable tower defense game, but it can also be a pretty savage one if you let your guard down for a second.
Fieldrunners ($0.99)Get it here
Fieldrunners 2 ($2.99)Get it here
A curious thing about some tower defense games is that they're essentially about war -- brutal war, no less -- but some engaged soldiers seem tickled about the whole thing. Look at the helmeted troopers decorating the icons for the Fieldrunners games. They're having a grand old time.
And, to be honest, you probably will too. The original Fieldrunners was one of the first prominent tower defense games for mobile, and meaning there's a relatively straightforward experience to be had, here. Nevertheless, it's pretty involved, and developer Subatomic Studios has gradually added more content over the years.
Fieldrunners 2 operates on the same principle as its predecessor (survive!!), but there are more weapons, more complex AI, and a tower that launches live bee hives.
Bloons TD series (Various prices)Get it here
Who needs soldiers with bombs when you can have monkeys with nail guns? There are several Bloons TD games available on the App Store, and though each one adds new levels, new towers, and new monkeys, the premise is the same throughout: There's a line of balloons attempting to slip past you, and by all the lice-eating primate ancestors that preceded you, you cannot allow that to happen.
So you have a darts. You have towers, too. And you have a passel of games that is not only extremely simple to learn, but also offers up some of the most satisfying sound effects you'll hear in a mobile game. Pop! Pop! Pop pop pop!
Kingdom Rush ($0.99)Get it here
Kingdom Rush Frontiers ($2.99)Get it here
Kingdom Rush Origins ($2.99)Get it here
It takes a lot of work to keep a kingdom running. You have to tax your citizens. You have to feed the guardian dragon. And most importantly, you have to defend against all oncoming threats, a challenge the Kingdom Rush series is very serious about.
Kingdom Rush is classic tower defense through-and-through. You fight across different types of terrain, keeping an eye on approaching orcs and wizards while laying down and upgrading your towers. Certain towers specialize in wasting certain enemies, so keep that in mind in the interest of smart spending.
Or just blow all your cash and go down in a blaze of glory. You're the King. Nobody can tell you what to do, really.
geoDefense ($1.99)Get it here
geoDefense Swarm ($1.99)Get it here
Whereas most tower defense games opt for a military or medieval theme, geoDefense breaks free of literality in favor of a geometric neon field and vaguely-defined foes. But those bold visual decisions are part of why geoDefense's war against the "Creeps" is still fondly remembered when tower defense enthusiasts reminisce about their favorite games.
Developer Critical Thought Games had a tough act to follow with the next entry in the series, geoDefense Swarm. Swarm opts for a more open-ended style of defense, which ups the necessity for player strategy a tad. Despite their differences, both games are must-haves.
Jelly Defense ($2.99)Get it here
Infinite Dreams' Jelly Defense brings us the best jelly-based battles the world has seen since the Smucker's-Welch's War of '65. You build towers to help your wobbly friends defend their energy crystals from lines of thieves, though you have to be careful because your foes can only be damaged by like-colored weapons.
Succeeding in Jelly Defense requires trail-and-error -- towers must be placed in specific indentations -- but it's a goo tower defense game overall.
Royal Revolt (Free)Get it here
Perusing higher education won't put you into life-shattering debt if you're royalty, but it leaves your realm way open to takeovers from know-it-all relatives. Royal Revolt is about taking back what's rightfully yours (or what you believe is rightfully yours, anyway).
To do so, you need to actually take control of your troops and storm "your" fortified castle. Royal Revolt's "reverse tower defense" gameplay is an interesting change from the norm, plus it offers you the chance to throw a very expensive tantrum that ends in violence.