It's a recipe you'll know well if you've already played other Starcraft II releases, and it's easy to understand why the designers have stuck with it. The base missions typically feature some sort of gimmick - like having to defend against waves of attacking Zerg, only the Zerg are moving through narrow canyons, letting you use the high ground to your advantage. As in the main game, missions vary between the type where you build up your base to mass an army and defeat the enemy, and the ones where you control a single hero unit, maybe alongside a few basic units as well.
