Tower defense

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Tower defense is a subgenre of real-time strategy video games,[1][2] where the goal is to stop the enemies from reaching a specific point on the map by building a variety of different towers which shoot at them as they pass. Enemies and towers usually have varied abilities, costs, and upgrade prices. When an enemy is defeated, the player earns money or points, which are used to buy or upgrade towers, or upgrade the number of money or points that are earned, or even upgrade the rate at which they upgrade.[3]

The choice and positioning of the personal towers is the essential strategy of the game. Many games, such as Flash Element Tower Defense feature enemies that run through a "maze", which allows the player to strategically place towers for optimal effectiveness.[4] However, some versions of the genre force the user to create the maze out of their own towers, such as Desktop Tower Defense.[5] Some versions are a hybrid of these two types, with preset paths that can be modified to some extent by tower placement, or towers that can be modified by path placement.


A prototypical tower defense game was the Atari Games release Rampart in 1990.[6] By the early 2000s, maps for StarCraft, Age of Empires II, and Warcraft III were following in Rampart's footsteps.[6] The Fort Condor strategy minigame in Final Fantasy VII may also have inspired the tower defense genre as it contains several elements that are now genre mainstays.

Eventually, independent video game developers began using Adobe Flash to make stand-alone tower defense browser games,[7] which led to the release of Flash Element Tower Defense in January 2007[8] and then Desktop Tower Defense in March of the same year.[9][10] Desktop Tower Defense became immensely popular and earned an Independent Games Festival award,[11] and its success led to a version created for the mobile phone by a different developer.[12] Several other tower defense video games achieved a level of fame, including GemCraft[13] and Plants vs. Zombies.[14]

By 2008, the genre's success led to tower defense games on video game consoles such as Defense Grid: The Awakening on the Xbox 360,[15] and PixelJunk Monsters and Savage Moon for the PlayStation 3.[6] Tower defense games have also appeared on handheld game consoles such as Lock's Quest and Ninjatown on the Nintendo DS.[16]


A screenshot of Defenders of Ardania showing the genre's characteristic towers, as well as units and a castle that serves as an end point

Tower defense games are characterised by the positioning of static units by the player to defend against mobile enemy units who are trying to get from a start point to an end point. There is a set number of enemy units (or 'damage' the player can take from units reaching the end point) who can reach the end point before the level is lost. Some games use a static route that the enemy units follow around which the player places their towers, while others favour a free-form environment that allows the user to define the path the enemy units take. Some games use a mixture of both. Most games allow the upgrading of the player's towers.

Often an essential strategy is "mazing", which is the tactic of creating a long, winding path of towers to lengthen the distance the enemies must traverse to get past the defense. Sometimes "juggling" is possible by alternating between barricading an exit on one side and then the other side to cause the enemies to path back and forth until they are defeated. Some games also allow players to modify the attack strategy used by towers to be able to defend for an even more reasonable price.[17]

The degree of the player's control (or lack thereof) in such games also varies from games where the player controls a unit within the game world, to games where the player has no direct control over units at all.

It is a common theme in tower defense games to have air units which do not pass through the layout of the maze, but rather fly over the towers directly to the end destination.

Some tower defense games or custom maps also require the player to send out enemies to their opponents' game boards respectively their controlled areas at a common game board. Such games are also known as tower wars games.

USPTO trademark[edit]

On June 3, 2008, COM2US Corporation was awarded the trademark for the term "Tower Defense", filed on June 13, 2007 - serial number 3442002. The corporation is reported to have started enforcing the trademark: in early 2010, developers of games on Apple's App Store reported receiving messages requiring name changes for their games, citing trademark violation.[18][19] Adding the phrase "Tower Defense" (in capital letters) to the description of an app submission to iTunesConnect and the app store automatically triggers a warning that the submission is likely to be rejected for use of the term; however, writing the phrase in lower case is still acceptable as "tower defense" is a valid description of a game style.


  1. ^ Dugan, Patrick (January 30, 2007). "Slamdance, Post-Columbine - Personal Conversations with Freaks and Geeks". Gamasutra. Archived from the original on August 4, 2013. 
  2. ^ Remo, Chris; Sheffield, Brandon (July 11, 2008). "Interview: Soren Johnson - Spore's Strategist". Gamasutra. Archived from the original on October 14, 2012. 
  3. ^ Rutkoff, Aaron (June 20, 2007). "Strategy Game Pits Players Against Desktop Invasion". Wall Street Journal. Retrieved August 31, 2013. 
  4. ^ Scott, David. "Flash Element Tower Defense". Retrieved April 15, 2009. 
  5. ^ Preece, Paul. "Desktop Tower Defense". Retrieved September 25, 2008. 
  6. ^ a b c Mitchell, Luke (June 22, 2008). "Tower Defense: Bringing the genre back". PALGN. Retrieved December 24, 2008. 
  7. ^ Walbridge, Michael (June 12, 2008). "Analysis: Defense of the Ancients - An Underground Revolution". GamaSutra. Archived from the original on May 21, 2013. 
  8. ^ Jay (January 11, 2007). "Flash Element TD". Jayisgames. Archived from the original on August 28, 2013. 
  9. ^ Cario, Erwan (November 10, 2007). "Jouer plus pour travailler moins Jeux vidéo. Sélection de petites douceurs en ligne, dangereusement addictives.". Libération. Archived from the original on July 26, 2008. 
  10. ^ Remo, Chris (November 18, 2008). "Interview: Flash Tower Defense Creators On VC Deal, Social Gaming Site". Gamasutra. Archived from the original on October 15, 2012. 
  11. ^ "2008 IGF Awards Topped By Crayon Physics Deluxe". Gamasutra. February 21, 2008. Archived from the original on May 20, 2013. 
  12. ^ Roush, George (December 5, 2007). "Tower Defense Review". IGN. Archived from the original on March 30, 2013. 
  13. ^ W., Tim (June 13, 2008). "Best Of Indie Games: Rose, Camellia, Ziczac & Nameless". Gamasutra. Archived from the original on October 23, 2012. 
  14. ^ Ambrozy, Brian (November 20, 2009). "Plants vs. Zombies nominated for PC Game of the Year". Icrontic. Icrontic. Archived from the original on August 13, 2012. 
  15. ^ Kelly, Kevin (August 30, 2008). "PAX 2008 hands-on: Defense Grid: The Awakening". Joystiq. Weblogs. Archived from the original on October 28, 2012. 
  16. ^ Hatfield, Daemon (September 22, 2008). "Ninjatown Multiplayer Hands-on". IGN. Archived from the original on October 21, 2012. 
  17. ^ "CreepTD manual". Retrieved February 13, 2012. 
  18. ^ Jordan, Jon (January 25, 2010). "Com2uS "guides" developers not to use its trademark Tower Defense". Archived from the original on May 30, 2013. 
  19. ^ Slashandburn/Mgate Labs (January 21, 2010). ""Tower Defense" is now up for CP Infringement". Touch Arcade. Retrieved May 8, 2015.