They're constantly finding ways to try to get you to spend money. I'm surprised they don't charge you for opening the app. For example, one of the missions daily missions is fight in 27 pvp battles. You only charge 1 pvp energy an hour. That's 24 pvp energy in a day. That means you have to buy energy to complete the mission. They need to scale down the perks for each character. I swear every character has invincibility and it lasts long. Matches that should last a minute can go for 15 minutes.