Plants vs. Zombies is a game I've been eyeing for a while.  It regularly tempted me at $10 Steam with even cheaper sale prices.  This summer's sale finally put me over the edge.  Every so often you need some good tower defense action, and PvZ seemed like a unique yet highly praised take on the genre.  Its cartoonish, Popcap/flash feel and simple five-lane setup makes things perfect for beginners.  And it has enjoyed massive success over a huge variety of platforms.  Originating on PC, PvZ has since expanded to every modern platform imaginable, both traditional and mobile.  Popcap is undeniably a casual gaming powerhouse.  The Bejeweled and Feeding Frenzy creators certainly know how to make products and pricing that clicks with the average consumer.  They've been so successful that EA recently purchased the company for ~$750 million.

For the most part, PvZ exemplifies this success.  It creates a casual-friendly atmosphere with calculated progressive learning combined with enough longevity and a tad of optional difficulty to round out the complete package.  The game starts slowly, at first holding your hand with only a couple plant options (towers) available to defend your house from a weak zombie horde on a completely barren level.  With only five lanes to defend, beginners will learn quickly what it takes to operate.  In case they make mistakes, the game includes a get-out-of-jail-free card, in the form of zombie-clearing machines that activate and clear the lane should a zombie make it past the plants.  For a while, the game introduces a new plant on almost every level, encouraging the player to try them out and discover what they're worth.  Soon enough, juggling several plant types on more obnoxious levels will be a requirement.