Before every level, players can choose up to three birds (one extra from their Facebook friends in some levels) in their party, depending on the level. In the battle, enemies, mostly pigs, appear on a landscape. Battles may be normal, may involve multiple waves of enemies, or boss fights. To attack, players swipe from a bird to an enemy. To use a secondary skill (mostly defense types), the player taps the bird to use it on themselves, or swipes a bird into another bird to give it to the other bird. Whenever the birds attack or take damage, a “Rage Chili” indicator fills up at the bottom of the screen. When full, players can apply it to a bird to use their “rage” ability. After winning a battle, the players can earn up to three stars, depending on their performance in that battle. More stars indicates more resources that the players receive as a reward for winning the battle. The golden Lucky Coins, which are rare, are used to buy certain classes, spin the Golden Pig Machine for items, and to buy emergency consumables in battle. They can be earned by defeating a Golden Pig encountered across different levels, leveling up or through in-app purchases. The gameplay data can be backed up using a Rovio Account, which is now discontinued for registration As of May 2018[update], so only existing accounts can back up their gameplay data.