Your goal is to match three or more of one gem type in a horizontal or vertical line. You must do this by swapping gems with one another. Swapping gems can only be done between two gems at a time, and causes them to switch positions if the swap will create a match. You can swap a gem with another gem that is directly above, below, to the left, or to the right of it. It might sound a bit complicated, but it's fairly simple in practice.