Tower defense

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Tower defense (TD) is a subgenre of strategy games where the goal is to defend a player's territories or possessions by obstructing the enemy attackers or by stopping enemies from reaching the exits, usually achieved by placing defensive structures on or along their path of attack. [1] This typically means building a variety of different structures that serve to automatically block, impede, attack or destroy enemies. Tower defense is seen as a subgenre of real-time strategy video games, due to its real-time origins, [2] [3] even though many modern tower defense games include aspects of turn-based strategy. Strategic choice and positioning of defensive elements is an essential strategy of the genre.

Contents

History

Precursors

The tower defense genre can trace its lineage back to the golden age of arcade video games in the 1980s. The object of the arcade game Space Invaders, released in 1978, was to defend the player's territory (represented by the bottom of the screen) against waves of incoming enemies. The game featured shields that could be used to strategically obstruct enemy attacks on the player and assist the player in defending their territory, though not to expressly protect the territory. The 1980 game Missile Command changed that by giving shields a more strategic role. In the game, players could obstruct incoming missiles, and there were multiple attack paths in each attack wave. [4] Missile Command was also the first of its kind to make use of a pointing device, a trackball, enabling players to use a crosshair. The innovation was ahead of its time and anticipated the genre's later boom, which was paved by the wide adoption of the computer mouse. Additionally, in Missile Command, the sole target of the attackers is the base, not a specific player character. For these reasons, some regard it as the first true game in the genre. [4]

While later arcade games like Defender (1981) and Choplifter (1982) lacked the strategy element of Missile Command, they began a trend of games that shifted the primary objective to defending non-player items. In these games, defending non-players from waves of attackers is key to progressing. Parker Brothers' 1982 title Star Wars: The Empire Strikes Back for the Atari 2600 was one of the first tie-ins to popularize the base defense style. The concept of waves of enemies attacking the base in single file (in this case AT-ATs) proved a formula that was subsequently copied by many games as the shift from arcade to PC gaming began. Players were now able to choose from different methods of obstructing attackers' progress. [5] Sorcerer's Apprentice for the Atari 2600 featured Mickey Mouse and was first published in 1983.

Green House, a popular 1982 handheld game by Nintendo Nintendo Game&Watch - Green House.jpg
Green House, a popular 1982 handheld game by Nintendo

Nintendo's popular 1980s Game & Watch handheld games featured many popular precursors. With their fixed sprite cells with binary states, games with waves of attackers following fixed paths were able to make use of the technical limitations of the platform yet proved simple and enjoyable to casual gamers. Vermin (1980), one of the first, tasked players with defending the garden (a theme followed by many later games) from relentless horde of moles. The following years saw a flood of similar titles, including Manhole (1981), Parachute (1981), and Popeye (1981). 1982 saw multiple titles with the primary object of protecting buildings from burning: Fire Attack, Oil Panic and Mickey & Donald. The later titles utilized multiple articulating screens to increase the difficulty for players. With two screens these games introduced basic resource management (e.g. oil and water), forcing players to multitask. Green House (1982) was another popular two screen game in which players use clouds of pesticide spray to protect flowers from waves of attacking insects. Despite the early rush of archetypal titles, ultimately there was a general decline in fixed-cell games, due to their technical limitations, simplistic gameplay, and the rise of personal computers and handhelds the Game Boy; correspondingly, this genre also declined. A rare exception was Safebuster (1988 multi-screen) in which the player protects a safe from a thief trying to blow it up.

By the mid-1980s, the strategy elements began to further evolve. Early PC gaming examples include the 1984 Commodore 64 titles Gandalf the Sorcerer, a shooter with tower defense elements, and Imagine Software's 1984 release Pedro . Pedro, a garden defense game, introduced new gameplay elements, including different enemy types as well as the ability to place fixed obstructions, and to build and repair the player's territory. [6]

Modern genre emerges

Rampart , released in 1990, is generally considered to have established the prototypical tower defense. [7] Rampart introduced player placed defenses that automatically attack incoming enemies. In addition, it has distinct phases of build, defend and repair. These are now staple gameplay elements of many games in the genre. It was also one of the first multiplayer video games of its kind. [8]

While Rampart was popular, similar games were rarely seen until the widespread adoption of the computer mouse on the PC. The DOS title Ambush at Sorinor (1993) was a rare exception from this era. [8] Tower defense gameplay also made an appearance on consoles with several minigames in the Final Fantasy series, including a tower-defense minigame in Final Fantasy VI (1994) [9] and the Fort Condor minigame in Final Fantasy VII (1997), which was also one of the first to feature 3D graphics. Attack of the Mutant Penguins for the Atari Jaguar and MS-DOS was released in 1995. Dungeon Keeper (1997) had players defend the Dungeon Heart, a gigantic gem at the centre of your dungeon, which, if destroyed, would cause the player to lose the game. [10] Fortress was released for the Game Boy Advance in 2001.

As real-time strategy games gained popularity in PC gaming, many introduced tower defense modes in their gameplay, particularly in multiplayer. In February 2006, the custom maps for Warcraft III (2002), Element TD and Gem Tower Defense, which were initially created in Warcraft III World Editor , almost single-handedly rekindled the genre. [7] These titles would also bring role-playing elements to the genre for the first time.

2007–2008 boom

Between 2007 and 2008, the genre became a phenomenon, due in part to the popularity of the tower defense mode in real time strategy games, but mainly due to the rise of Adobe Flash independent developers as well as the emergence of major smartphone app stores from Apple and Google. The first stand-alone browser games emerged in 2007. [11] Among them were the extremely popular titles Flash Element Tower Defense released in January, [12] Desktop Tower Defense released in March [13] [14] and Antbuster released in May. [15] [16] Desktop Tower Defense earned an Independent Games Festival award, [17] and its success led to a version created for the mobile phone by a different developer. [18] Another significant Flash title released in 2008 was GemCraft . [19] Handheld game console were not ignored in the boom and titles included Lock's Quest and Ninjatown released in September and October respectively. [20] Bloons Tower Defense was first published in 2007, one of many in a series of balloon themed multi-platform games released.

The genre's success also led to new releases on PC and video game consoles. Popular 2008 titles included PixelJunk Monsters released in January, Defense Grid: The Awakening [21] and Savage Moon in December. [7] Also released in 2008 were geoDefense Swarm , geoDefense , GemCraft , Fieldrunners , Harvest: Massive Encounter and Crystal Defenders . GauntNet was released in April 2009. [22] Plants vs. Zombies released in May 2009 was another highly popular tower defense which became a successful series on mobile devices. [23] Also released that year were Sentinel , TowerMadness , Babel Rising , Creeper World , Sol Survivor , Comet Crash , Final Fantasy Crystal Chronicles: My Life as a Darklord , South Park Let's Go Tower Defense Play! , Starship Patrol and Trenches .

With the arrival of Apple's App Store tower defense developers adapted quickly to the touchscreen interface and the titles were among the most downloaded, many of them ported directly from Flash. Among the more notable include Kingdom Rush , first released in 2011, which sold more than seventeen million copies both on App store and Play store.

A new breed of 3D games

A screenshot from Defenders of Ardania Defenders of Ardania 2.jpeg
A screenshot from Defenders of Ardania

By the end of the boom, most tower defense games were still using side scrolling, isometric, or top-down perspective graphics. Iron Grip: Warlord , released in November, 2008 unsuccessfully pioneered the first person perspective shooter with the genre. [24] The awkward combination of experimental tower defense mechanics with 3D graphics was not well received, but later titles refined its execution paving the way for a popular new breed of games. Dungeon Defenders , released in October 2010, was one of the first tower defense games to bring the genre to the third person perspective. It sold over 250,000 copies in first two weeks of release [25] and over 600,000 copies by the end of 2011. [26] 2010 saw the release of SteamWorld Tower Defense , Protect Me Knight , The Tales of Bearsworth Manor , Revenge of the Titans , Arrow of Laputa , Toy Soldiers and Robocalypse: Beaver Defense .

The 2011 title Sanctum , and its 2013 sequel popularized the first person shooter hybrid that was pioneered by these earlier games. [27] Orcs Must Die! also integrated the FPS genre into a fully 3D environment and went to have several sequels. Anomaly: Warzone Earth released in 2011 introduced a variation of gameplay which has been described as "reverse tower defense", [28] "tower attack", [29] and "tower offense". [30] In the game, the player must attack the enemy bases protected by numerous defenses. Sequels and other games have since experimented further with both styles of tower defense. [31] Tiny Heroes , Army of Darkness: Defense , Iron Brigade , Rock of Ages and Trenches 2 were also released in 2011.

Defender's Quest , Bad Hotel , Toy Defense , Strikefleet Omega , Unstoppable Gorg , Defenders of Ardania , Orcs Must Die! 2 , Fieldrunners 2 , Dillon's Rolling Western , Oil Rush and Elf Defense Eng all came out in 2012. Around this period the genre matured, gaining recognition as a distinct sub-genre of strategy games and returning in numerous upgraded versions. Chain Chronicle and CastleStorm were released in 2013. Plants vs. Zombies 2 came out and Prime World: Defenders featured deck-building mechanics. 2014 saw a number of brand new titles including Space Run , Dungeon of the Endless , Island Days , Final Horizon and The Battle Cats as well the return of Age of Empires: Castle Siege , Defense Grid 2 and TowerMadness 2 . Deathtrap and Krinkle Krusher were first published in 2015.

More recent titles in the genre include Rock of Ages 2: Bigger & Boulder (2017) and Orcs Must Die! Unchained (2017), Dillon's Dead-Heat Breakers (2018), Eden Rising: Supremacy (2018), Aegis Defenders (2018), Bloons TD 6 (2018), Arknights (2019), Taur (2020), Element TD 2 (2020), Buster's Tower Defense (2021), and Path to Nowhere (2022).

With the advent of social networking service applications, such as the Facebook Platform, tower defense has become a popular genre with titles such as Bloons TD and Plants vs. Zombies Adventures making the transition to turn-based play. [32] Recent releases include Star Fox Guard and McDroid which came out in 2016.

On the platform Roblox, many Tower Defense games have been created, the most notable being Tower Defense Simulator ("Paradoxum Games", 2019) as well as the first famous one being Tower Battles (Planet3arth, 2017). These games are mostly 3D and multiplayer based, with features like matchmaking and elevators being used to pair users up. However these are not the only tower defense games on Roblox. There are also a large number of other tower defense games: many spinoffs of Tower Defense Simulator and a few original titles.

Gameplay

Simple 1-bit tower defense game for Arduboy Tower defense (micro td).gif
Simple 1-bit tower defense game for Arduboy

The basic gameplay elements of tower defense are:

What distinguishes tower defense base defending games from other base defending games (such as Space Invaders, or other games where bases are defended) is the player's ability to strategically place, construct or summon obstructive constructions and constructive obstructions in the path of attacking enemies.

In a tower defense, the player's main character is often invincible, as their primary objective is the survival of the base rather than the player.

Some features of modern tower defense:

Many modern tower defense games evolved from real-time to turn-based, cycling through distinct gameplay phases such as build, defend, repair, and celebrate. Many games, such as Flash Element Tower Defense feature enemies that scamper through a "maze", which allows the player to strategically place "towers" for optimal effectiveness. [34] However, some versions of the genre force the user to create the "maze" out of their own "towers", such as Desktop Tower Defense . [35] Some versions of the genre 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, or modifications that can be placed by tower paths. Often an essential strategy is "mazing", the tactic of creating a long, winding path of towers (or "maze") 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 tantalizingly reasonable price. [36]

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, or even no control over the game whatsoever.

A common theme in tower defense games to have occasional "air" units which ignore the layout of the board (i.e. maze paths or obstructions) and travel directly to the end destination, or enemies which prioritize different targets than their main destination.

Some tower defense games or custom maps also require the player to not only defend their own board but send out enemies to attack their opponents' game boards (or opponent-controlled areas of a common game board) in return. Such games are also known as tower wars game boards.

USPTO trademark

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. [37] [38] 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.

Related Research Articles

Real-time strategy (RTS) is a subgenre of strategy video games that does not progress incrementally in turns, but allow all players to play simultaneously, in "real time". By contrast, in turn-based strategy (TBS) games, players take turns to play. The term "real-time strategy" was coined by Brett Sperry to market Dune II in the early 1990s.

<i>Rampart</i> (video game) 1990 video game

Rampart is a 1990 video game released by Atari Games and Midway Games that combines the shoot 'em up, strategy, and puzzle genres. It debuted as an arcade game with trackball controls, and was ported to home systems. It had a limited US release in October 1990, and a wide release in early 1991. It was distributed in Japan by Namco.

Tactical role-playing games, also known as strategy role-playing games and in Japan as simulation RPGs, are a video game genre that combines core elements of role-playing video games with those of tactical strategy video games. The formats of tactical RPGs are much like traditional tabletop role-playing games and strategy games in appearance, pacing, and rule structure. Likewise, early tabletop role-playing games are descended from skirmish wargames such as Chainmail, which were primarily concerned with combat.

<i>Dungeons & Dragons: Tower of Doom</i> 1994 arcade game

Dungeons & Dragons: Tower of Doom, published in 1994, is the first of two arcade games created by Capcom based on the Dungeons & Dragons tabletop role-playing game and set in the Mystara campaign setting. It is a side scrolling beat 'em up with some role-playing video game elements for one to four players. The game was also released on the Sega Saturn, packaged with its sequel, Dungeons & Dragons: Shadow over Mystara, under the title Dungeons & Dragons Collection, although the Saturn version limited the gameplay to only two players. In 2013, both games were re-released for modern platforms as Dungeons & Dragons: Chronicles of Mystara.

An action role-playing game is a subgenre of video games that combines core elements from both the action game and role-playing genre.

A beat 'em up is a video game genre featuring hand-to-hand combat against a large number of opponents. Traditional beat 'em ups take place in scrolling, two-dimensional (2D) levels, while a number of modern games feature more open three-dimensional (3D) environments with yet larger numbers of enemies. The gameplay tends to follow arcade genre conventions, such as being simple to learn but difficult to master, and the combat system tends to be more highly developed than other side-scrolling action games. Two-player cooperative gameplay and multiple player characters are also hallmarks of the genre. Most of these games take place in urban settings and feature crime-fighting and revenge-based plots, though some games may employ historical, science fiction or fantasy themes.

<i>Desktop Tower Defense</i> 2007 video game

Desktop Tower Defense is a Flash-based tower defense browser game created by Paul Preece in March 2007. The game had been played over 15.7 million times as of July 2007, and was one of Webware 100's top ten entertainment web applications of 2007. Desktop Tower Defense is available in an English, Spanish, German, French, or Italian interface. In May 2009, a commercial Nintendo DS version became available.

Strategy is a major video game genre that emphasizes thinking and planning over direct instant action in order to achieve victory. Although many types of video games can contain strategic elements, as a genre, strategy games are most commonly defined as those with a primary focus on high-level strategy, logistics and resource management. They are also usually divided into two main sub-categories: turn-based and real-time, but there are also many strategy cross/sub-genres that feature additional elements such as tactics, diplomacy, economics and exploration.

<i>Defense Grid: The Awakening</i> Tower defense video game first released in 2008

Defense Grid: The Awakening is a tower defense video game developed by Hidden Path Entertainment for Windows and Xbox Live Arcade on the Xbox 360. The game was one of the titles promoted by Microsoft during their Game Developers Conference keynote speech on February 20, 2008. The game was released for Microsoft Windows on December 8, 2008, and for Xbox 360 on September 2, 2009. The OS X version shipped from Virtual Programming on July 7, 2010.

<i>Crystal Defenders</i> Two tower defense video games by Square Enix

Crystal Defenders is a set of two tower defense video games developed and published by Square Enix. The games use the setting of Ivalice and design elements from Final Fantasy Tactics A2: Grimoire of the Rift, forming part of the wider Final Fantasy franchise. The games feature a selection of characters sporting Final Fantasy-based character classes, and play out tower defense scenarios against recurring series of monsters. The first game in the series is Crystal Guardians, which was released in three parts for Japanese mobile phones in 2008. It was adapted for iOS later that year as Square Enix's first game for the platform, and renamed Crystal Defenders. Under that name, the game was also released between 2009 and 2011 for Android, Xbox Live Arcade, WiiWare, and PlayStation 3 and PlayStation Portable via the PlayStation Store. It was re-released with graphical improvements for iOS as Crystal Defenders Plus in 2013. A sequel, Crystal Defenders: Vanguard Storm, was released for iOS in 2009.

<i>Bloons Tower Defense</i> Video game series by Ninja Kiwi

Bloons Tower Defense is a series of tower defense games under the Bloons series created and produced by Ninja Kiwi. The game was initially developed as a browser game, built upon the Adobe Flash platform and released in mid 2007. Later games in the series expanded to support various mobile platforms, including Android, iOS, Windows Phone, PlayStation Portable, Nintendo DSi, Windows, Linux and MacOS. Games in the Bloons series older than Bloons TD 6 are available through the Ninja Kiwi Archive on Steam.

<i>Bloons</i> Video game series

Bloons is a video game franchise developed by Ninja Kiwi. The games involve players using monkeys, armed with various tools, to pop as many "bloons" (balloons) as possible. They include the Bloons series, the Bloons Tower Defense series, and several other spin-offs. Most of the earlier Bloons games are browser-based games that use Adobe Flash Player, although some are available on other platforms. Mobile games based on the Bloons series are distributed through the App Store, Google Play, and some through Steam. Games made by Ninja Kiwi older than Bloons TD 6 are available through the Ninja Kiwi Archive on Steam.

<i>ProtoGalaxy</i> 2010 video game

ProtoGalaxy is a cross-genre video game for Microsoft Windows that was released on October 6, 2010. In the game's back-story, a species of powerful, unknown extraterrestrials enters the Milky Way with the intention of enslaving its inhabitants. The player characters must defend Earth from this alien threat and restore human civilization. ProtoGalaxy is a 2.5D game; the 2D playing field employs 3D graphics. ProtoGalaxy incorporates elements of a variety of gaming genres, such as adventure, arcade, shooter, puzzle, and role-playing genres.

<i>Dungeon Defenders</i> 2010 video game

Dungeon Defenders is a hybrid multiplayer video game developed by Trendy Entertainment that combines the genres of tower defense and action role-playing game. It is based on a showcase of Unreal Engine 3 named Dungeon Defense. The game takes place in a fantasy setting where players control the young apprentices of wizards and warriors and defend against hordes of monsters. A sequel titled Dungeon Defenders II was released in 2015.

Kixeye is a video game company founded in July 2007 and headquartered in Victoria, British Columbia, Canada. The company creates, develops and publishes massively multiplayer online real-time strategy games (MMORTS) for PC and mobile devices. Kixeye gained popularity as a pioneer in midcore action games featuring real-time combat on the social networking website Facebook. Following their initial launch, Kixeye's games generated twenty times more revenue per daily active user than other social games, retaining active users five times longer on average.

<i>Kingdom Rush</i> 2011 video game

Kingdom Rush is a tower defense game developed by Ironhide Game Studio and published by Armor Games. It was released on July 28, 2011, as a browser game, followed by ports for iOS in December 2011, Android on May 13, 2013, and Windows and macOS on January 6, 2014. In the game's medieval fantasy setting, players take control of a general serving under King Denas of Linirea, who must defend the land from an onslaught of evil monsters. Each level is composed of a number of pre-set roads, which the player can place defensive towers around to fight off the approaching monsters. Slaying enemies gives the player gold, which they can use to buy new towers or upgrade existing ones to improve their capabilities.

Ninja Kiwi, previously known as Kaiparasoft Ltd, is a mobile and online video game developer founded in Auckland, New Zealand, in 2006 by brothers Chris and Stephen Harris. Ninja Kiwi's first game was a browser based game called Cash Sprint, developed on the Adobe Flash Platform. Since then, they have produced more than 60 games across platforms including Adobe Flash, Android, iOS, PlayStation Portable, Nintendo DS, and more recently, Steam. Their most well-known titles are the Bloons and Bloons Tower Defense games. In 2012, Ninja Kiwi purchased Digital Goldfish, a Dundee, Scotland-based developer, for an undisclosed sum.

<i>Dungeon of the Endless</i> 2014 video game

Dungeon of the Endless is a roguelike tower defense game developed and published by Amplitude Studios. It is the third game of their loosely connected Endless series, which includes Endless Space and Endless Legend. It was released in October 2014 for Microsoft Windows and OS X, August 2015 for iOS, and for Xbox One in March 2016. The PlayStation 4 and Nintendo Switch ports were released in May 2020. A revamped version for iOS and Android devices, called Dungeon of the Endless: Apogee, was released in March 2021 by Playdigious.

<i>Bloons TD 6</i> 2018 tower defense video game

Bloons TD 6 is a 2018 tower defense game developed and published by Ninja Kiwi. The sixth entry in the Bloons Tower Defense series, it first released on June 13, 2018, for iOS and Android. It was later released on Microsoft Windows in December 2018, and macOS in March 2020 via Steam. It was later released in Epic Games Store on June 19, 2022. In February 2022, Bloons TD 6+ was released for Apple Arcade. On June 12, 2023, Bloons TD 6Netflix was released on iOS and Android for Netflix members only. On September 5, 2023, it was released on Xbox One/Xbox Series X, with a PlayStation 4/5 release planned for a later date.

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