When hordes of zombies head at you at one time, it's a complete rush. You hurry to place your plants and collect your sunlight as if nothing else matters. As you progress in the game, you unlock mini games and a survival mode. It really gets tough when a creeping fog is introduced. While Plants vs. Zombies is a terrific experience, it's not as tough as, say, Sony's PixelJunk Monsters, which, with each level, features a different layout and approach paths for the creeps who deign to destroy your kingdom. Yet it's just as cute and charming and almost as hard to beat.