Keyblade War has a fairly open battle system.
You can use any commands you have over and over again, but try not to god. Items can be used the number of times usable/the number you have. Potions heal a specified amount.
In battle, each command has a specific damage value or other effect. When you use a damaging command, you add its damage value to your magic or attack value, depending on the type of attack. You do that much damage, unless someone dodges or block.
To dodge, you roll the dodge die. You add your speed to the number shown. The enemy rolls the aim die and adds it to his or her speed. The one with the higher speed wins (you dodge, they hit). If you tie, roll again. If you are only one apart, half damage is done.
To block, you roll the block die. If it is a 1, blocking fails. If it is a 2, you block. You subtract your defense from the damage and that amount of damage is done.
Cure commands use the cure die. If it is a 1, 2, or 3, cure fails. If it is a 4, 5, or 6, it succeeds and the appropriate damage is healed. You must wait and use some other attacks while you heal.
Other bonuses are added to your stats in battle.
To do a normal attack, you add your attack value to your attack stat and do that much damage.