Command & Conquer: Red Alert 2 is built on the Tiberian Sun engine. From a technical viewpoint the two games are all but similar, with the notable difference of the engine drawing 2D sprites for units in place of Tiberian Sun’s more complex voxels. But gameplay-wise it’s a slightly different experience.
Having identified Red Alert’s fast pace as what set it apart, the developers have modified the engine to recapture that pace. In accord with their philosophy that they want half-hour multiplayer games, not three-hour games, they have increased the speed at which units move and at which units and structures are created. By dividing the interface into separate tabs, they have increased the speed at which you can build, and by balancing buildings and units “high”, meaning in essence that all units have both rigid strengths and weaknesses, they ensure that battles are resolved quickly.