Pop-up duels are a gameplay element from the Chocobo series. Playing much like Rock-Paper-Scissors, the player will choose cards from their hand to combat the cards the opponent possesses. Each player has a Health Point (HP) gauge showing the their remaining health, and a Crystal Points (CP) gauge showing which special attacks may be used.
In a pop-up duel, each player may draw up to three cards during their first turn. During the first phase of each turn, the player has 15 seconds to choose which card they are going to play. There is no way to know what cards the opponent has to choose from, but during this phase the player is able to see the colors of all the cards in the opponent's hand.
The player selects a card by sliding it up to the top screen with the stylus. The player who makes their selection faster will always move first, unless Slow or Haste is in play. If Slow is in play, the affected player will move second; if Haste is in play, then the affected player will move first.
After each card has had it's chance to attack then each player will draw one new card to replace the one they just used. It is possible to draw the same card that was just played. The duel ends once one player's HP reaches zero.
It can become very easy for a player to defeat the computer after many duels, because all of the opponents use the same cards in the same order. This never changes, so it is possible to memorize the order of the cards opponents will use.
The CP gauge is used to perform special attacks; which attacks can be used depends upon the color of the crystals that make up the gauge. This gauge is filled by playing colored cards; during the End Phase of one's turn, the color of the card played is added to the CP gauge. CP will be added to the gauge even if a card's attack fails. Gray cards will not add CP to the gauge, as it possesses no color.
The CP gauge is only able to hold 10 crystals, and the crystals added earliest will be replaced after the gauge fills up completely.
Cards can use special attacks called Crystal Abilities. These abilities require you to have at least a specific amount of CP of certain colors. Using a Crystal Ability does not get rid of the CP stored in the gauge.
Using a crystal ability does not remove CP stored in the gauge, so if a player had red CP x1, blue CP x1, green CP x2, and yellow CP x3 before using Ultima Weapon's Ultima (red CP x1, blue CP x1, green CP x1, and yellow CP x2) and their attack hit, they would still have all their CP (Ultima Weapon is a gray card and does not add any CP to the gauge). However, some crystal abilities effect CP by changing the color or removing them.
Pop-up cards are earned from minigames and by completing secrets in picture books. Minigames award players with two cards for clearing silver and gold level scores. These cards can be added to one of six decks that can be used in pop-up duels. For the first pop-up duel one will only be able to use a three-card deck, which cannot be revised. But after that Dueler X will give Chocobo a trainer deck, which can hold one deck of eight cards. Eventually, another deck will obtained which can hold up to six different decks with 15 cards each.
There is only one of each card and it can be either red, blue, yellow, green, or gray. Most cards also have an effect that is triggered after a successful attack or defense. For example, Lamia can use Song, which will inflict Silence on the opponent if the players' attack connects. Certain cards have a shine to them, these cards have the potential to be stronger than their counterpart card, and end in a "+". For example, Iron Giant can use Overhead Smash, which deals 3 damage, but if Chocobos' HP is lower than the opponents it will deal double damage. Iron Giant can also use Overhead Smash+, which deals 4 damage, but if Chocobo's HP is lower than 5 it will deal double damage.
Each card also has red, blue, yellow, and green zones used for determining if an attack is successful. Each of these zones contains a picture of a sword, shield, or is left blank. If a card had a picture of a sword in its yellow zone, then it would check what picture was in the yellow zone on the opposing card. If there is a shield in the opposing card's yellow zone, then the attack has failed. If there is a sword in the opposing card's yellow zone, then the attack connects but only deals half the normal damage.
If the opposing card's yellow zone is blank then the attack is successful and will deal normal damage. Some cards have no sword icon in any of their zones. This means that these cards cannot attack, but most of these have multiple shield icons and an effect that is triggered when they successfully defend against an attack.
Several cards were added to the Duels to enhance the system:
- Guard Break, represented by a Spear. Guard Break can only apply damage when the Spear on the attacking Card matches up with the defending card's Shield. It will fail if it matches up with a Sword or Blank space.
- Burn - Doubles damage from a red magic ring.
- Freeze - Doubles damage from a blue magic ring.
- Numb - Doubles damage from a yellow magic ring.
- Poison - Doubles damage from a green magic ring.
- Silence - Prevents use of crystal abilities.
- Protect - Halves damage received.
- Haste - First strike on next turn.
- Slow - Second strike on next turn.