At the Weapon Shop, if a Digger appears, get it. Also, get as many underground weapons as you can (for example, Worm, Homing Worm, Hotfoot, etc.). When the battle starts, fire every weapon except for the Digger or underground weapons. Then, select the Digger and change the angle of the shot so that it goes diagonally into the ground. On your next turn, move into the underground tunnel and start firing your underground weapons. Your enemy cannot hit you because you are underground, but you can still hit your enemy.