Even Flow is a great game and is all about grouping the darts. You throw 10 throws and you only score if you hit 2 or 3 in the same field. For example you hit S20 + s5 + S20 = S20 x 2 = 40 points.

Once you've scored in a field, the field is locked, and you can't score in that field any more.

If you're aiming for T20 and hit S5 with your first dart, you can choose strategy and continue at S5 to at least try to get a few points, or try to hit T20 with the last two darts for a better score. But then you might risk locking S20 and only get 40 points with the next two darts...