There are already too many tower defense games on the App Store. There are great ones, good ones, OK ones and bad ones, and there are plenty of each category. Castle Doombad -- the latest from the always solid Adult Swim Games -- proves it deserves to exist two reasons: First, rather than adopting the familiar top-down viewpoint that most tower defense games utilize, it's presented in a two-dimensional castle with multiple floors going up. And second, you play as the villain. Awesome.
Each level of Castle Doombad revolves around a captured princess, and it's up to you to make sure she remains captive. She produces "screams" at regular intervals which act as in-game currency to buy traps and barriers. You place these obstacles wherever you think they'll best be able to hold off the heroes who are attempting to rescue the damsel. These mechanics are the same as many games in the genre, but they are presented in a fresh and fun way.
The 2D nature of the levels presents unique challenges as well, such as heroes who use ladders to skip entire floors of your castle. Don't expect to load the first floor of your fortress with traps and relax; you'll need to build traps and spawn minions almost everywhere to ensure the princess remains under lock and key.
There's a surprising amount of depth to the game, and you can try out various strategies to see which works the best for you. For example, sometimes it's best to pick off each hero as they enter your castle, while other times it pays off to place a barrier and build up a huge group of them before wiping out the crowd with a single trap. Regardless of your approach, it's quite satisfying to watch the tiny knights and other rescuers meet their demise at your hand.
Adult Swim Games hits another home run with Castle Doombad, and whether you're new to the tower defense genre or a seasoned veteran, it's definitely worth the US$2.99 price of entry. You don't get many chances to play as the villain these days, and even rarer is it this much fun.