There are few instructions given for this game, but it is not too difficult to figure out what to do. Each of your three ships have differing strengths and weaknesses that become apparent very quickly. The smaller ships have a smaller range and less power to their shots, but they can move very quickly. The larger ships have a larger range and more powerful shots, but they often move too slowly to catch up with the pirate ships. You must learn to take advantage of the strengths of each ship or your base will surely fall.
Skull and crossbones on the border of the screen indicate the position of an oncoming pirate ship and give you a little time to prepare your counter attack. To attack the pirate ships, simply draw a line of attack from your ship to where you want it to travel. Be sure to take into account not only where the pirate ship is now, but where it will be by the time your ship gets to its destination. It took me a little while to get used to adjusting my attack routes taking into account both ships speed and direction.