How in the world can the object of the game NOT be to score as many points as possible? Take a look at the high scores list and see what's at the top - Looks like the highest scores to me, but maybe I'm mitaken.
And the boards get RIDICULOUSLY easy when you are down to 2 and 3 colors. At that point, you need to be careful to NOT clear the board. Well, assuming you are trying for a high score, like everyone else, I mean.