The free version of Plants vs Zombies by PopCap Games is basically a short demo of the actual game, which is categorized as a defense game. Defense games can vary in style, but they share several core characteristics. The basic concept is that you, the player, must protect your base of operations from waves of enemies. Doing so is accomplished by killing the invaders with weapons of some kind and preventing the destruction of your land. Hence, the reason why the 'defense' moniker is attached to the genre.In the Flash version of Plants vs Zombies, your base is your suburban home, and the weapons you use are plants; the zombies are your foes. You place your plants on your lawn, which serves as the battleground. If any zombie gets to the end of your side of the lawn, you lose.
The demo lets you play three different modes: adventure, survival and puzzle. I have played several defense games in the past, so completing the adventure section of the short demo was not that hard. It consists of about 20 stages, half of which takes place in the daytime and the other half taking place at night. The game provides a couple of minigames as well, breaking up the monotony of regular missions. For example, instead of planting and fighting hordes as usual, you also get to play a bowling minigame at one point, in which you roll nuts at the approaching zombies.
The survival mode is much more difficult than the other categories. It allows you a set number of weapons each round, and you must survive against multiple waves of enemies. The reason why this is hard to accomplish is because the game gets very laggy (i.e. very slow and unresponsive) when there are too many zombies being rendered. Because survival relies on spawning a lot of zombies to attack you, it really can bog down the game's performance; I have experienced this same problem in another zombie defense game where a massive number of opponents were created and slowed down the game considerably. I played on an older computer that had a 2.4ghz CPU and only 512MB of memory, so that may have influenced the slowdown. In any case, the lag that is experienced really affects the mechanics because you cannot plant as fast or as often as you like. In a survival game, that is crucial to winning.
Puzzle mode is quite fun and different than the other 2 modes; it does not rely on planting or building defenses in the same way as adventure or survival mode. Rather, a number of pots are placed on your lawn. Breaking open a pot will reveal either a zombie or a weapon. You must figure out how to destroy the zombies using only what you can find in the pots. Break too many at the same time, and you may either be granted a lot of weapons or a lot of zombies depending on your luck. It is challenging but not frustrating to a fault.
Another positive part of Plants vs Zombies is the design. The concept of plants fighting zombies is amusing by itself, but the colorful graphics and subtle touches to the game make it a well-thought out product. The snow pea, for example, is a plant that shoots icy peas, and there are a variety of zombies, ranging from one that can polevault and another dressed in football garb.
In addition to the performance problem in the later stages of survival mode that I pointed out, the free version also has a pop-up of another PopCap game that greets you when you visit the webpage. It is not too inconvenient, but it must be noted.
Plants vs Zombies may not be a revolutionary game of its type, but it does make the game fun and accessible to almost anyone. The Flash version is free, so there is not much risk in playing it. It appears to have one or two optimization problems, but those can be overlooked for the enjoyment one experiences. I have seen prices for the retail game to range from $5.00 to $20.00. It is relatively cheap compared to other computer games, so you may be open to buying the full version after testing the demo out.