Plants and zombies aren't exactly what you'd call natural enemies, given the latter's single-minded hunger for brains and the former's complete lack thereof. Despite being brainless, plants apparently appreciate the hand that waters them, so when zombie hordes come to eat your brains, it's Plants vs. Zombies. To protect your own gray matter, you create defensive fortifications around your house by cultivating a wide variety of cute, combat-ready plants to handle the goofy varieties of zombie attackers. Plants vs. Zombies is solidly rooted in the tower defense genre, but it grows and branches in such a charming, accessible way that almost anyone can pick it up and have a lot of fun. The basic gameplay is pleasantly engaging, but it will take seasoned defenders a few hours before they can play legitimately challenging levels. Fortunately, Plants vs. Zombies rolls out new units and environments at a good pace, and the minigames, puzzles, and Survival mode offer some clever and challenging diversions. It's a delightful game that is both addictive and accessible, and you'll never look at your garden the same way again.
The core action is quite simple. Your lawn is divided into a grid, and each square can hold one plant. Zombies shamble up the rows of the grid toward your house, and if they get past your defenses, well, you know. At the top of the screen there are a number of slots that house the various plants at your disposal. Setting a plant down in a square costs sunlight, a resource that falls intermittently from the sky. However, you need more sunlight than is freely available, so you have to plant sunflowers to generate more sunlight. During the first minutes of a level, it's a measured balancing act between building your sunflower ranks and laying down defenses to deal with the first few zombies. Your basic attack units shoot peas down the row that they are planted in, so you'll need one in each row before too long. As the zombies become more numerous, you bolster your botanical battalion with a growing variety of projectile launchers, defensive barriers, attack amplifiers, and one-use weapons of zombie destruction. After you've survived the final wave of zombies, you're rewarded with a new minigame, a new type of plant, or perhaps just a hastily scrawled note from your would-be assailants.
Variety and creativity take this basic mission structure and turn it into something special. Just when you've gotten your daytime defense strategy down, the zombies decide to attack at night and you have a whole new set of plants to manage. When you've taken care of the nocturnal nasties, it's back to the daytime, only now a few of your rows are taken up by your backyard pool (there are snorkel zombies). New units come along that fit the new environments, and this steady trickle of new elements helps keep the gentle difficulty curve from becoming dull. Still, tower defense veterans will have to endure a lot of simple, familiar action in order to find a real challenge, and the wait may prove too long for some. Fortunately, all of the units are cleverly realized and adorably animated. Happy sunflowers bob merrily as they fuel your defense efforts, and pole-vaulting zombies jog toward your house with gangly athleticism. From angry jalapenos to spacy wall-nuts, each unit has a great sense of personality, and the first time you watch a dancing zombie moonwalk onto your lawn and summon his garishly dressed backup dancers, you'll likely chuckle with amusement. The visual charm makes the game a pleasure to look at, and it helps keep things feeling fresh.
Once you've completed the main adventure and unlocked most of the units, the Survival mode offers a number of stages in which you can seek a tougher challenge. Each Survival stage is basically a bunch of increasingly difficult levels strung together. In both Adventure and Survival mode, you get a preview of the zombie types to expect, so you can array your defenses accordingly. Certain zombies can bypass certain defenses; for example, the balloon zombie floats over normal projectiles, but you can plant a cactus to shoot him down. In Survival mode, adjusting for these midstage changes might mean that you have to uproot some of your plants to make room for strategically crucial ones, or just push your established perimeter out further toward the zombie invaders. Unlike in the Adventure mode, your defenses are persistent throughout each level and you get the chance to change your plant loadout periodically. Building on established defenses is an interesting tactical twist and is a great opportunity to use some of the more exotic species that you may not have used in your Adventure mode strategy. This all adds up to make Survival mode surprisingly rewarding. It offers new tactical challenges and a reason to play beyond the main adventure.
There are some other fun reasons to continue playing after completing Adventure mode, namely puzzles and minigames. There are two types of puzzle game: Vasebreaker and I, Zombie. In the first, you are given a lawn with a number of nondescript vases on it. You have to break them all to win, but you never know what will pop out. It might be a zombie, or it might be a helpful plant. You have to dispatch all of the zombies to survive, and doing so with improvised defenses is fun and hectic. I, Zombie turns the tables and lets you deploy the zombies. Busting through each row of plant defenses requires that you use your strategic knowledge for evil; and, in a delightfully morbid twist, you'll actually enjoy the sound of zombies chewing on plants. The minigames are a wacky assortment of one-off challenges that further play with the basic dynamics of Plants vs. Zombies. Some games pit you against modified enemies (zombies with plants for heads; invisible zombies), whereas others mess with your planting strategy (planting entire columns at once; mysterious portals that redirect your projectiles). With 20 levels of puzzles and 20 different minigames, Plants vs. Zombies offers a lot of entertaining ways to keep playing.
Of course, satisfaction for a well-defended lawn isn't your only reward. You can earn money throughout every mode, which you can then spend on a variety of items offered by your crazy neighbor, who sells things out of the back of his car. Items range from defensive boosts, to upgrades for your existing plants, to a wide variety of gardening implements to help you cultivate your Zen gardens. These areas are simple greenhouses in which you can grow your exotic plants in a zombie-free environment. The music helps set the Zen vibe and is quite good across the board. It generally consists of lighthearted, progressive loops that bop along at a good pace and set a great tone for the action.
It's impressive how well everything works together in Plants vs. Zombies. Every element, from the gameplay to the bonus extras to the presentation, seems to follow the core philosophy of accessible simplicity underpinned by thoughtful complexity. It is well suited for a wide range of audiences, but those who seek a challenge may not have the patience to play through the few hours that it will take to encounter the more difficult levels. For frugality's sake, interested parties are advised to purchase it from Valve's download service, Steam, where it is selling for $9.99 (as opposed to $19.99 on PopCap's Web site). Plants vs. Zombies is fun, funny, and a great buy at either price.