If you haven't had a chance to play a version of Plants vs. Zombies
yet, then either you don't like tower defense games, or you don't know what you are missing. If it's the former, then Plants vs. Zombies
probably won't hold too much appeal for you. For the latter, on the other hand, this is a game that you must at least try out, and considering that the game has been released on pretty much every modern platform, you should be able to find a free demo somewhere.
The concept is simple, zombies are trying to get into your house and eat your brains. All that stands between you and the lumbering dead is your front lawn and the variety of plants you have to seed it with. These plants aren't your everyday vegetation though. They each have their own abilities, pros and cons, and you will need to use your sunlight, the currency of the game, wisely in order to put up a solid defense.
At first, you will start off with basic plants like Sunflowers, which produce more sunlight, and Pea Shooters. It isn't long before you start getting Potato Mines, Cherry Bombs, Wall-nuts [sic] and Snow Peas (a form of the pea shooter that slows down zombies).
The invading creatures walk across the screen to your house. They don't really vary in their paths, so you will be planting your various defensive forces on the same rows where they appear. So unlike other tower defense titles, there isn't a chance that the enemy will just walk by your plant - if it's in the way, it will get hit and the zombies will try and tear it down (well, eventually you will have to deal with jumping and balloon-riding zombies that can skip squares). As a result, its good to know how strong your various defenses are. One good example is the Wall-nut. While this plant doesn't do any actual damage, it can take a lot. Put this at the front of potentially vulnerable areas in order to slow down the horde so your damage-dealers can work on them longer.