Unlike most games, you don't just attack once on your turn in Xenogears. Instead, you can hit several times, depending on your AP. There are three kinds of attacks, Triangle Button, Square Button, and X Button attacks. Triangle attacks consume 1 AP, Square ones use 2 AP, and X buttons use 3 AP. You can execute as many attacks as you have AP for (your AP is refilled every turn).

   Note that there is no inherent advantage to any combination, as they all do the same amounts of damage (assuming they all hit) -- two Square attacks do the same amount of damage as four Triangles. That's where Deathblows come in. By executing certain patterns of buttons repeatedly (for example: Triangle, Square, X), your character can learn that Deathblow (they must also be at a high enough level). Once you've learned a Deathblow, pushing that sequence of buttons in battle will activate that Deathblow and deal extra damage.

   You can also store up AP by using some of your AP, then hitting Circle to cancel. Unused AP is stored in your Combo bar, and once you get enough AP there, you can use it all once to string together a bunch of Deathblows. This is generally useless, as they don't do any more damage than usual, and is only important in a few specific battles. It looks cool, though.

    Your maximum AP increases at the following spots:

4 AP	After Lahan Attack
5 AP	On the sandcruiser
6 AP	Once you get to Kislev
7 AP	After Shevat sequence