Originally released in 2009, PopCap’s "Plants vs. Zombies" has been played by millions of hardcore and casual gamers on just about every modern console, smartphone and tablet out there. A follow-up to the addictive tower defense game, "Plants vs. Zombies 2" is now available in the App Store as a free-to-play iOS exclusive. Like "Temple Run 2" and Rovio’s many "Angry Birds" variations, "Plants vs. Zombies 2" successfully evolves the franchise while retaining the delightfully simple zombie-blasting gameplay that keeps players coming back.

Story

You don’t play "Plants vs. Zombies" for the plot, but the sequel’s storyline is as lovingly absurd as the game’s title. Your eccentric companion, Crazy Dave, is back to deliver silly banter in between rounds, and after chowing down a taco, he decides that he wants to relive the experience of eating that very same taco again. The only way to settle this is through time travel, of course, so Dave’s mission sends you traveling through different eras and environments so that he can enjoy his cherished meal once more. Brilliant.

The time-traveling theme of "PvZ 2" allows for some much-welcomed stage variety, as the original game’s arenas were limited to similar-looking suburban lawns and rooftops. The game’s three main worlds are Ancient Egypt, Pirate Seas and the Wild West, each of which features its own unique zombies and environmental hazards.

Gameplay

Dedicated "Plants vs. Zombies" players will have no trouble jumping right back into the series’ familiar pick-up-and-play formula. For the uninitiated, "Plants vs. Zombies" is a tower defense game in which players must collect solar energy and use their points to strategically place a variety of combat-ready plants on their front lawn. Users must defend each stage from waves of the undead, which grow more powerful as the game progresses.

Like any worthy sequel, "Plants vs. Zombies 2" introduces a number of gameplay additions to shake things up. Players can now acquire and use plant food in the middle of a wave, which gives a temporary boost to any of your active plants. Plant food can be picked up from downed enemies or purchased with in-game coins, and the power-up has a different effect on each character in the game. We had a blast experimenting with the various effects of the food, which, for example, makes the sunflower spill out an excess of much-needed sun and turns the peashooter into an infinitely satisfying machine gun for a few seconds.

While "Plants vs. Zombies" is built on a rhythm of planting and waiting, the sequel’s combat upgrades make the action more engaging. After playing through a few stages of Ancient Egypt, you’ll be granted the ability to Power Pinch, Power Flick and Power Zap, which all allow you to defeat enemies with your fingers for a short time. Power Flick and Power Zap help give the game a "Fruit Ninja"-like immediacy, but we found Power Pinch to be a little less satisfying, especially on a small iPhone screen. Overall, PopCap made some significant upgrades to the game’s core formula, and we’ve never had so many different ways to knock down zombies with agriculture.

MORE: PS4 vs. Xbox One: Console Comparison

Graphics and Sound

The visual difference between "PvZ 2" and its predecessor is instantly noticeable, as all of the game’s characters and stages are significantly more animated. Even on an iPhone screen, we delighted in the rich colors and quirky movements of our peashooter every time it got ready to fire at a zombie. Even Crazy Dave has received plenty of new frames of animation, making him look, well... crazier. The new game worlds help spice up the overall aesthetic, from the sandy tornadoes of Egypt to the wooden floors of the pirate areas.

The "Plants vs. Zombies" games have always had great sound, and the sequel is no exception. The simple, soothing arrangements of the game’s stages make it easy to focus on the action, while zombie groans are creepily guttural. Both Crazy Dave and the Siri-like talking truck Penny have their own form of background gibberish to accompany the on-screen text, which helps give each character a bit more life.

Interface and Presentation

Whereas the original "Plants vs. Zombies" followed a linear progression, the worlds in "PvZ 2" have open-ended hubs that bring "Super Mario Bros." to mind. Although you’ll still be battling through the game’s main stages, you’ll occasionally have the chance to unlock doors that open up bonus levels. The game still rewards you with new plants and powers after you complete a level — except this time, they can be seen right on the map, so you’ll know exactly when you’ll earn them. When viewing the world map, players can check the in-game encyclopedia to keep track of the characters they’ve encountered and visit the in-game store to buy extra coins and upgrades.

MORE: 40 Best Free Apps for iPhone

The game starts you off in Ancient Egypt, and you must complete that world before you get to try out Pirate Land or the Wild West. While this is the status quo for most games in the "PvZ" realm, we would have liked to have had a quicker shot to try out all of the new environments.

Characters

It wouldn’t be a sequel if PopCap didn’t come up with new zombies to kill and new plants to kill them with, and the game’s new characters are as enjoyable as the power-ups that they come with. Some of your new allies include Bonk Choy, a melee fighter, and Bloomerang, a flower with projectiles that also hit enemies on the way back.

It’s nice that PopCap provided players with new peacekeeping plants, because the new "PvZ 2" enemies ramp up the overall difficulty. Egypt’s Ra Zombie can steal your much-needed sun if you’re not quick, and the Barrel Roller Zombie in Pirate Land can roll over any plants in his path. Seasoned "PvZ" players will certainly appreciate the curveballs provided by these new baddies.

In-App Purchases

Every free-to-play game relies on microtransactions to sustain itself, but PopCap never beats you over the head when it comes to making purchases. You can progress through the entire game just as you did on the original by finishing stages and unlocking more powerful plants. The in-app purchases are simply there for those who want to get through the game as quickly as possible.

Users can buy in-game coins, plants and upgrades, as well as special bundles that combine characters and power-ups. Coin packs start at $2.99 for 5,000, though you’ll get more coins for your money if you buy the bigger packages. Plants and upgrades cost up to $3.99 each, while the Starter Bundle gives you the squash plant, 5,000 coins and the shovel bonus for $4.99. Though it’s tempting to drop some cold, hard cash on extra coins so you’ll always have a devastating plant-food attack at the ready, the game is fun enough not to rush through.

Verdict

PopCap has done an excellent job bringing the "Plants vs. Zombies" franchise to new worlds, providing new characters and powers that you’ll be itching to try out. "Plants vs. Zombies 2" might not revolutionize the classic formula as the upcoming "Garden Warfare" spin-off is meant to, but it’s a thoroughly polished game that’s more than worthy of your iPhone or iPad. Although the current iOS exclusivity is disappointing, given the original version's wide release, we have a feeling "Plants vs. Zombies 2" will be too successful to stay on one platform for long.

Follow Mike Andronico @MikeAndronico and on Google+. Follow us @tomsguide, on Facebook and on Google+.