Shacknews writes: "Long ago, Blizzard admitted to itself that a singleplayer campaign does not prepare the player for competitive multiplayer in a real-time strategy game. In an effort to give novice players an offline arena in which to learn skills necessary for multiplayer, challenge mode was created.
Challenge mode will present players will three different levels of challenges, linked to achievements, that test different gameplay mechanics that aren't necessarily used in the campaign. The units in this mode are the same used in multiplayer. Each challenge has three award levels: bronze, silver, and gold."