Mission

The first missions is there to get you started. Whenever you don't know what to do, check the missions dialog. (Notice that you may have to expand the information by clicking on them.)

Later on the missions are there for your challenge. For every 10 missions you make, you gain a Level (no matter what type of mission it is). Currently a level increase gives you a little extended worker placement range besides the ranking in the level table in the score.