You always have the same amount as your opponent, and always have an equal amount of Mugic.
The default amount is 3, but you can have 1, 6, 10, 15 or 21 in your Creature deck. No-one of these are the same, as they all have different stats and a unique 12-digit code. These are the cards you play with, they each have different abilities. You always have 2 attack cards in hand, so you always have a chocie of what to play. When you've used them up, you can recycle your used cards. These are in your main play deck, where you can have 20 cards. Each card is unique, and has a 12 digit code, for use on the website.