Strategy games often involve other economic challenges. These can include building construction, population maintenance, and resource management. Strategy games frequently make use of a windowed interface to manage these complex challenges.
Most strategy games allow players to accumulate resources which can be converted to units, or converted to buildings such as factories that produce more units. The quantity and types of resources vary from game to game. Some games will emphasize resource acquisition by scattering large quantities throughout the map, while other games will put more emphasis on how resources are managed and applied by balancing the availability of resources between players. To a lesser extent, some strategy games give players a fixed quantity of units at the start of the game.
Strategy games often allow the player to spend resources on upgrades or research. Some of these upgrades enhance the player’s entire economy. Other upgrades apply to a unit or class of units, and unlock or enhance certain combat abilities. Sometimes enhancements are enabled by building a structure that enables more advanced structures. Games with a large number of upgrades often feature a technology tree, which is a series of advancements that players can research to unlock new units, buildings, and other capabilities. Technology trees are quite large in some games, and 4x strategy games are known for having the largest.
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.