Plants vs. Zombies is an adorable strategy game created by PopCap Games, the company responsible for some of the most beloved time sinks in the world. PvZ is less of an abstract puzzle game than PopCap's more famous offerings, but it is just as addictive and clever, and just as likely to halve your productivity for a long time.

Zombies are attacking your house, and you need to plant flowers to defend yourself. The playing grid is your lawn -- then later your backyard and your roof -- which is divided into squares, each of which can hold one plant. You start out with a basic attack plant (a "pea shooter") and a basic defense plant (a "wall nut"). You can also grow sunflowers which, in an inversion of real-world botany, produce sunlight -- the fuel you need to keep building more plants. If you're fighting during the day, you also acquire natural sunlight from time to time from the air; later, though, plants will be your only resource.

Each round, hilariously-animated zombies stagger across your lawn in an effort to get to your front door. The challenge is to arrange your plants wisely, on limited real estate, in order to keep the zombies from coming inside and eating you.

As the game progresses, the zombies get more clever: protecting themselves with football helmets or screen doors, jumping into your swimming pool wearing inner tubes, or even flying with the help of balloons. Each new threat can be countered by a new plant (the "cabbage-pult" can account for the angle of your roof; the "blover" blows flying zombies away), but only a limited number of plants can be taken on each mission, and all of them need to be supported with sunlight. At night, there is no natural sunlight at all, and you need to depend entirely on plants for your fuel. Fighting at night has its advantages, though; you can use mushrooms, nocturnal plants that are cheap to grow and often have very helpful effects. In between missions, your crazy neighbour, Dave, pops up occasionally to give you instructions and sell you bonus items.

The style of the game is sweet and cartoony, and surprisingly non-violent given the subject matter. Don't be fooled by the cute puns, though -- the gameplay is sophisticated, with lots of effects interacting with each other in subtle ways. The writing is very fine, too: the information on each zombie in the in-game encyclopedia (the "suburban almanac") is laugh-out-loud funny.

The game is well worth twenty bucks -- on sale for ten at Halloween! -- and offers some replayability by way of minigames and puzzles outside of the campaign. (In a callback to their most famous product, PopCap provides a version of Bejeweled called Beghouled.)

Plants vs. Zombies can be downloaded for the PC and the Mac at PopCap's website. You can also try a free Flash version here.