Command and Conquer had traditionally used a “right-pillar” control interface, with your map at the top. utility controls like “sell building” or “power down”, followed by a unit build selection screen. There you had 4 panels you could select between - “main base” buildings, defensive buildings, infantry, and vehicles - and you could scroll up and down a given panel. So long as you had the right production building, you could select things to build from anywhere on the map. If a unit had a “special ability”, it would be triggered by double-clicking on the unit.

Come 2003’s Command and Conquer: Generals, the UI had been totally redone to resemble the layout of Blizzard’s wildly popular Warcraft 3: The control panel now sat at the bottom of the screen, with the map on the left. Building a particular kind of unit required you to select the building or unit that produced it. Selecting an individual unit gave you a list of magic spells special abilities it could take, such as using an alternative weapon or purchasing a particular upgrade.