Just when you get jaded about genre derivations and overly "zany" aesthetics from the casual game sector, coupled with a sense of market saturation and imminent collapse oddly reminiscent of the US housing market, something like this comes along. Plants vs. Zombies is the latest hyper-polished, QAed-to-the-max casual fiesta from PopCap, a company whose success is driven by one part design innovation, three parts user testing, and two parts production value.
Take the typical tower defense model, parallelize it into rows, incorporate two alternative time-sensitive metrics, resources and the charge time between which certain types of towers (plants in this case) can be spawned. Balance the hell out of it until you have a finely-tuned matrix. The theme, which combines B-movie horror with the overlapping casual cliches of gardening and cuteness, is a loose enough touchstone for clever writers to come up with occasionally funny text and whimsically descriptive tower names, such as the "Wall-nut", the "Peashooter", the "Cherry Bomb" and the "etc. vine" that weaves it´s way up a trellis of level designs that vary like spiralling clockwork. They game is well crafted like the the Seattle equivalent of a Swiss wristwatch.
Beyond tight core mechanics delivered with the typical candied SFX and the too-shiny-to-be-2D graphics, the structure of the game is a textbook example of good unfolding of complexity. Each level, once completed, gives you a new plant with unique properties; these plants can interact in fairly interesting ways. At the beginning of each level you get a scope of the kinds of zombies you´ll be facing, and there are a wide variety, and then you must build a portfolio of plants to best counter their assault. A longer-term metagame involving coins (because you can´t have a casual game without the compulsive clink of metal money) allows you to buy rare upgrades and increase the size of your portfolio. Each set of levels gives you two bonus levels where plant cards roll up on a conveyor rather than being purchased with the core resource, and each set of levels also varies the terrain. Even though TD games, especially ones without speed-up functions, are pretty much filler generators by definition, this one feels almost devoid of it. It´s rather like the Braid of the sub-genre, not to be confused with Immortal Defense, which could more aptly be described as the Planescape: Torment of TD.
What´s perhaps a trademark of PopCap´s design style is that all their games make it challenge, and paradoxically therefore "fun," to lose. You get a safety, French socialism-style, in all of their stuff, from the generous free balls of Peggle to the lawnmower last-line of defense in most of the levels of this game. Since sudden death is a frustrating binary situation in most tower defense games, this design structure is a pretty solid move for the genre. But what´s more interesting is how these games cauterize any sense of failure, making it opium-like in the sense of infantile comfort, in the false sense of accomplishment, which is really, combined with the addictive incremental churn of numbers, the selling point. Perhaps it is the sellers in this society who are the plants and the buyers who are the zombies, and the outcome cannot be said too soon.