Technology tree

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Freeciv-2.1.8 technology tree.png
Freeciv-2.1.8 technology tree.png
One part of Freeciv ’s technology tree. Note the complex dependencies between technologies.

In strategy computer games, a technology, tech, or research tree is a hierarchical visual representation of the possible sequences of upgrades a player can take (most often through the act of research). Because these trees are technically directed and acyclic, they can more accurately be described as a technology directed acyclic graph . The diagram is tree-shaped in the sense that it branches between each 'level', allowing the player to choose one sequence or another. [1] Each level is called a tier and is often used to describe the technological strength of a player. Typically, at the beginning of a session of a strategy game, a player will start at tier 1, and will only have a few options for technologies to research. Each technology that a player researches will open up one or more new options, but may or may not, depending on the computer game, close off the paths to other options. The tech tree is the representation of all possible paths of research a player can take, up to the culmination of said sequence.

A hierarchy is an arrangement of items in which the items are represented as being "above", "below", or "at the same level as" one another. Hierarchy is an important concept in a wide variety of fields, such as philosophy, mathematics, computer science, organizational theory, systems theory, and the social sciences.

Research formal work undertaken systematically to increase the stock of knowledge

Research comprises "creative and systematic work undertaken to increase the stock of knowledge, including knowledge of humans, culture and society, and the use of this stock of knowledge to devise new applications." It is used to establish or confirm facts, reaffirm the results of previous work, solve new or existing problems, support theorems, or develop new theories. A research project may also be an expansion on past work in the field. Research projects can be used to develop further knowledge on a topic, or in the example of a school research project, they can be used to further a student's research prowess to prepare them for future jobs or reports. To test the validity of instruments, procedures, or experiments, research may replicate elements of prior projects or the project as a whole. The primary purposes of basic research are documentation, discovery, interpretation, or the research and development (R&D) of methods and systems for the advancement of human knowledge. Approaches to research depend on epistemologies, which vary considerably both within and between humanities and sciences. There are several forms of research: scientific, humanities, artistic, economic, social, business, marketing, practitioner research, life, technological, etc.

Directed acyclic graph directed graph with no directed cycles

In mathematics, particularly graph theory, and computer science, a directed acyclic graph, is a finite directed graph with no directed cycles. That is, it consists of finitely many vertices and edges, with each edge directed from one vertex to another, such that there is no way to start at any vertex v and follow a consistently-directed sequence of edges that eventually loops back to v again. Equivalently, a DAG is a directed graph that has a topological ordering, a sequence of the vertices such that every edge is directed from earlier to later in the sequence.


A player who is engaged in research activities is said to be "teching up," "going up the tech tree," or "moving up the tech tree." Analysis of a tech tree can lead players to memorize and use specific build orders.

In strategy computer games, of both the turn-based and real-time varieties, a build order is a linear pattern of production, research, and resource management aimed at achieving a specific and specialized goal. They are analogous to chess openings, in that a player will have a specific order of play in mind, however the amount the build order, the strategy around which the build order is built or even which build order is then used varies on the skill, ability and other factors such as how aggressive or defensive each player is.


Classic research

The Classic tech tree is the one where extensive research into new technologies must be conducted parallel to the progression of a game. Some real-time strategy (RTS) games as well as most turn-based strategy (TBS) games employ this type of tech tree. In these games, players typically have a 'command center', 'unit-training-facility' and 'research facility' at their disposal from the start, allowing them to both start research into more advanced technologies, or engaging in combat with enemies using the basic units ( Warzone 2100 , Mega Lo Mania , Master of Orion series, Civilization series, Space Empires series).

Real-time strategy (RTS) is a subgenre of strategy video games where the game does not progress incrementally in turns. This is distinguished from turn-based strategy (TBS), in which all players take turns when playing.

A turn-based strategy (TBS) game is a strategy game where players take turns when playing. This is distinguished from real-time strategy (RTS), in which all players play simultaneously.

Warzone 2100 video game

Warzone 2100 is an open-source real-time strategy and real-time tactics hybrid computer game, originally developed by Pumpkin Studios and published by Eidos Interactive. It was originally released in 1999 for Microsoft Windows and PlayStation, and is now also available for macOS, FreeBSD, AmigaOS 4, AROS, MorphOS, Linux, NetBSD and OpenBSD.


In some games, the requirement of an actual research facility is absent. In this case players can allocate research points, or in-game resources to purchase new technologies. In some games the allocation yields direct results, meaning that procuring the new technology isn't paired with allotted time for the research of said technology to complete.


In most RTS games the technology tree consists of buildings which must be built in a specific sequence, which in turn unlocks new technologies. These newly unlocked technologies can be more advanced units, upgrades for research or more advanced buildings. ( StarCraft , Command & Conquer Series.)

StarCraft is a military science fiction media franchise, created by Chris Metzen and James Phinney and owned by Blizzard Entertainment. The series, set in the beginning of the 26th century, centers on a galactic struggle for dominance among four species—the adaptable and mobile Terrans, the ever-evolving insectoid Zerg, the powerfully enigmatic Protoss, and the "god-like" Xel'Naga creator race—in a distant part of the Milky Way galaxy known as the Koprulu Sector. The series debuted with the video game StarCraft in 1998. It has grown to include a number of other games as well as eight novelizations, two Amazing Stories articles, a board game, and other licensed merchandise such as collectible statues and toys.

Command & Conquer (C&C) was a real-time strategy (RTS) video game franchise, first developed by Westwood Studios. The first game was one of the earliest of the RTS genre, itself based on Westwood Studios' influential strategy game Dune II and introducing trademarks followed in the rest of the series. This includes full-motion video cutscenes with a notable ensemble cast to progress the story, as opposed to digitally in-game rendered cutscenes. Westwood Studios was taken over by Electronic Arts in 1998 and closed down in 2003. The studio and some of its members were absorbed into EA Los Angeles, which continued development on the series.

Prerequisites for technology advances

In most types of strategy games, the player needs particular buildings in order to research specific technologies or build specific advanced units ( StarCraft , Total Annihilation ), while in other games upgrades/technologies are unlocked through research of their parent technology research ( Warzone 2100 ). In many TBS games the prerequisite is one or more lower-level technologies, with no dependency on specific buildings ( Master of Orion series, Civilization series, Space Empires series). [2] [3] [4] Most strategy games however use both systems. both requiring dedicated buildings and in advanced cases pre requisite technology, sometimes culminating in a game ending super-weapon of some kind.

<i>Total Annihilation</i> video game

Total Annihilation is a real-time strategy video game created by Cavedog Entertainment, a sub-division of Humongous Entertainment, and released on September 30, 1997 by GT Interactive for Microsoft Windows and Mac OS. Two expansion packs were released, The Core Contingency on April 30, 1998 and Battle Tactics on June 30, 1998. After the closure of the Cavedog Entertainment in 1999, the intellectual property fell to Infogrames.

<i>Master of Orion</i> video game

Master of Orion is a turn-based, 4X science fiction strategy game released in 1993 by MicroProse on the MS-DOS and Mac OS operating systems. The game is the first in its franchise, and the rights are held by Wargaming. The player leads one of ten races to dominate the galaxy through a combination of diplomacy and conquest while developing technology, exploring and colonizing star systems.

Space Empires is a series of 4X turn-based strategy games by Malfador Machinations that allow the player to assume the role of the leader of a space-faring civilization.


The structures of tech trees vary quite widely. In the simplest cases (e.g. Master of Orion ) there are several completely separate research areas and one could research all the way up to the highest level in one area without researching other areas (although this would often be far from ideal). In more complex cases[ citation needed ] (e.g. Civilization ) every technology above the starting level has more than one prerequisite and one has to research most of the lower-level technologies in order to research any of the top-level technologies. And there are many possibilities between these two variants, for example in Space Empires researching to a specified level in one field may enable the player both to research to a higher level in that field and to start research in a new field which was previously not available. [2]

Major 4X games like Civilization and Master of Orion have a much larger technology tree than most other strategy games; as an extreme example, Space Empires III has over 200 technologies. [5] [6]

Availability of technologies

Some RTSs make different techs available to different races or cultures (especially StarCraft ; but many RTSs have special units or buildings for different cultures, e.g. Age of Empires expansion pack and later versions, Red Alert 2 ). Most TBSs make all technologies available to all cultures (e.g. Civilization ). Master of Orion (original version) is a complex special case in this respect: the full tree is the same for all; but in each game each player gets a subset of the full tech tree that depends on which race was selected.

Balance between civilian and military techs

In many RTS games tech advances are almost exclusively military (e.g. StarCraft ). But in most TBS and some RTS games the research and production costs of top-end military techs are so high that you have to build up your economy and your research productivity first (RTS – Age of Empires and Empire Earth , where one of the most significant costs is going up an epoch; TBS – the Civilization series and Master of Orion series).

What happens after researching everything

In many games there's nothing useful to do and the player may scrap research centers to save maintenance costs and/or devote the resources to something else ( Space Empires series).

In later installments of the Civilization series the last technology (called "future tech") represents an amalgamation of all possible future discoveries and can be researched repeatedly. In Civilization V , it increases a player's score, while in Civilization IV it raises the health and the happiness in the empire. Note that to reach the last technology in Civilization V, all spaceship technologies required to win must also have been discovered, so the game will likely be nearing its conclusion.

In the Galactic Civilizations series the final technology solves the nature of existence, and is victory.

In the Master of Orion series more advanced research reduces the size and cost of spaceship components, and "hyper-advanced" research in areas which have military applications therefore enables players to build more high-tech weapons into a given ship size and at lower production cost.

In Rise of Nations , the final four technologies result in such an advantage that the game will likely end quickly. Also, the "knowledge" resource needed to research is also used late in the game to produce cruise missiles and nuclear weapons.


Typically the board game Civilization by Francis Tresham (1980) is given the credit of introducing a technology tree. Sid Meier’s Civilization (1991) is considered as an iconic computer strategy game for using them. Since Civilization, technology trees have been used in various digital games [7] . Likewise, the first creation of a technology tree as a mechanism refers to Civilization [8] .

The arcade shoot 'em up Gradius used a power-up system functionally identical to a tech tree in 1985[ citation needed ].

Tech trees started showing up in turn-based strategy games in the early 1990s[ citation needed ]. The 1991 video game Mega Lo Mania had a tech tree with a system of research levels/epochs that allowed the deployment of better units and defences and is considered to be the first game to combine a technology tree into a Real-time strategy game. The video game Civilization , also released in 1991, was probably the first turn-based strategy game to feature the same basic structure of tech trees seen in games today[ citation needed ].

See also

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  1. Rollings, Andrew; Ernest Adams (2006). Fundamentals of Game Design. Prentice Hall.
  2. 1 2 See the relevant games' manuals.
  3. Master of Orion (1993), the Galactic Civilizations series and Sword of the Stars have no research buildings; players simply allocate some of each colony's output to research (see game manuals). In the Civilization series (1991 onwards) and Master of Orion II (1996) one can do research without buildings, but it's much faster when supported by the right buildings (see game manuals). In the Space Empires series (1993 onwards) and in Ascendancy (1995) research can only be done via buildings, but these can research any technology (see game manuals).
  4. "RTS Basics: R & D". and the StarCraft manual. Although multi-epoch games like the Age of Empires and Empire Earth series have a larger number of research options and a significant proportion of civilian research options, the research options all depend on having the right buildings. See the relevant games' manuals.
  5. "Joystiq interview: Ironclad talks 4X strategy with Sins of a Solar Empire". February 1, 2008. Retrieved 2008-06-14.
  6. In Warcraft III one can reach the highest level of one branch of the technology tree in five steps; Master of Orion (original version) has 10 levels per subject, and 2 to 5 technologies per level; the Civilization IV technology tree requires nearly 60 steps to reach the end (see game manuals).
  7. Heinimäki 2015, p. 21.
  8. Ghys, Tuur. "Technology Trees: Freedom and Determinism in Historical Strategy Games". Retrieved 13 November 2017.