Final Fantasy Crystal Chronicles: The Crystal Bearers/Final Boss

Final boss
Before you are ready to face Weiss, you should consider going back and getting as powerful as you can, by leveling up your health from defeating monsters and by buying good accessories from the shops.

The battle starts simply enough. Whack some crystal machines around and try to pull the metal of the ship, while remembering to keep moving, as you're going to need the health. After you've done this, a big arm will come out and attempt to hit you. At this point don't worry about the crystal machines or the metal, just focus on the arm, which will swing in one of three ways:
 * 1) Sideways: To dodge, just go to the far right, down left, up then right back to your starting position.
 * 2) Upwards: Go left up, then go back to the upper right position.
 * 3) Downwards: Stay at the upper right and you should be fine.

While you're dodging, try to get one piece of the arm off. Don't worry about the others; if you manage to destroy this bit, the rest will fall. A good time to get hits in is while you're dodging the sideways strike. Once this is done, quickly get rid of the metal and the machines for health.

During the second part you will want to go for the guns first, because when you blow them up they damage the arm.