Matilda, Terence and the elderly Shirley, as well as the Mighty Eagle. Birds can only be leveled-up outside of battles, where a bird that wants to level up would be fused with another bird that is then discarded, and once their level cap is reached, the player must spend evolution material to "evolve" them, raise their level cap and generally increase their power rating. The game has a single-player campaign mode where players set out on a quest to stop the pigs from imperiling the Angry Birds' eggs as usual, as well as thwart the schemes of Bacon Corp and its leader Don Bacon, and involves traveling across multiple zones of the game world, each with different terrain. Most areas will empower birds of a certain plumage, allowing them to inflict twice as much damage, and every time a battle is won, it cannot be played again. After every few battles, however, the player will be unable to advance further until two missions are completed by sending out scouts to collect items or reveal battles that can be fought. Up to three scouts can be deployed at once (unless the clan scout is activated), but players must wait one hour before each one can be used again, or skip the wait by paying gems or feeding berries to the exhausted scouts. It is also possible to participate in player-versus-player matches, which take place in the Oink-tagon, or wherever scouts reveal such a battle. Two players take turns using their bird squads to knock pigs towards their opponent's half of the arena so that they will attack their squad, but can also defeat the pigs to automatically damage the opponent or otherwise gain a small advantage against their opponent. The player who drains their opponent's health bar wins. Players are ranked by how well they play in arena matches in a week-long season, and are rewarded proportionally based on their performance. Since an update in spring 2018, each season may have new rules that grant bigger ranking jumps to players who win with a certain combination of birds, as well as buffs or nerfs to the pigs and/or birds in the arena. Players can also join clans for perks in battle. Perks are unlocked depending on the clan's level. The clan perks are clan buffs: have clan health and clan smartbomb, clan egg: get an extra egg after winning battle (excluding