Defense Games

Defense games are a genre of game in which the player must prevent enemies from reaching some target by the careful placement and choice of fixed defenses, often referred to as towers. Typically, players are also able to upgrade towers as the game continues, so that as the game progresses their basic defenses can become increasingly powerful.

The spiritual ancestor of defense games is Rampart, an arcade game from 1990, in which players had to place cannons to defend a castle, while repairing damage dealt by enemies between waves. Recognizable defense games were created in user-made levels in games such as Starcraft and Warcraft in the late 1990s. However, it wasn't until 2007 that the now-ubiquitous Flash defense games made their first appearance.

They have recently become extremely popular. Besides the Flash in-browser defense games, there are stand-alone defense games for nearly every platform: From the PC to the iPhone to the Xbox and PS3. Plants Vs Zombies, a defense game, was even nominated for PC Game of The Year in 2009.

People seem to like them because they're very easy to play, yet difficult to master. The basic goal is simple enough: keep the bad guys from getting to their target. But the way in which you do that can contain many levels of complexity. Is it better to have lots of weak defenders or a few strong ones? How do the different sorts of defenses work together? Where do you put them on the map? And depending on the game, there can be even more advanced strategic questions.

Designers like them because there's a lot of room to be distinctive in the genre. What do you want the upgrade tree to look like? Do you want to make the player think more about careful placement, or about upgrade strategies? What kind of graphics do you want to have---cartoonish, realistic, or something in between? As well, there's plenty of decisions to be made about game mechanics, as we'll see below.

For example, there's the choice of fixed-path games versus maze-builders. In a fixed-path game, the path the enemies will take is set, and the player needs to choose where to place their towers. These often involve levels that are essentially a puzzle to be solved.

On the other hand, in maze-builders, the player is essentially designing the level themselves, as the enemies' path is set by the defenses placed by the player---meaning the player has to think about where they want the bad guys to go. Of course, you can go an intermediate route, for example by blocking off part of the map while allowing maze-building in a remaining section.

So, for example, Bloons Tower Defense is a fixed-path game with fairly cartoonish graphics. Defenses and enemies are based on the popular series of Bloons puzzle games: Enemies are balloons (or bloons) while defenses are dart- and bomb-based.

Many times you will find yourself defending a castle in defense games. Many castle defense games exist where you will find an onslaught of enemies coming towards your castle. This is just one more example of the many different types of defense games.

Hopefully this brief introduction has given you a taste of what defense games are about. Now, get out there and start playing!