Technology tree

Typically, at the beginning of a session of a strategy game, a player will start at tier 1, which offers only a few options for research.

The Classic tech tree is the one where extensive research into new technologies must be conducted parallel to the progression of a game.

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).

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 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.

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.

[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].