The Trooper has a standard Match-3 setup, except for the top of the board, which depicts an animated battle between your character on the left and invading forces from the right. Matching three on the board affects action on the battle above. All of the board pieces correspond to enemies. For example, matching three or more helicopters fires three missiles at any helicopters on the path, or just gives you points if there aren't any. If they make it to your sandbagged fort, it's game over.
Points go toward promotions, while little more than titles, do help give more purpose to the game. There is definite strategy involved, especially when deciding between waiting for more enemies before matching pieces or trying to amass points as they take their sweet time trying to reach you.