What is the changes?

Compared to the original StarCraft, StarCraft II was designed to focus more heavily on the multiplayer aspect, with changes that include major improvements to Battle.net, a new competitive "ladder" system for ranked games, and new matchmaking mechanics—designed to "match-up" players of equal skill level. In addition, the replay function, which allows players to record and review past games, was improved. Blizzard also stated they incorporated changes to the game that were suggested by fans. StarCraft II continues its predecessor's use of pre-rendered cinematic cut scenes to advance the plot while also improving the quality of in-game cut scenes within the levels themselves, which are rendered on-the-fly using the same game engine as the graphics in the game proper. Blizzard states that with the new graphics engine that StarCraft II uses to render the gameplay, they "can actually create in-game cut-scenes of near-cinematic quality". Most Protoss and Terran units, and some Zerg units, have been shown on the StarCraft II official website, and in several video demonstrations held by Blizzard. Improvements include advanced scenery allocation and more detailed space terrain, such as floating space platforms with planets and asteroids in the background. Small cliffs, extensions, and even advertising signs were also shown to have been improved and refined.