When playing a level, you have 5 attempts to try and complete it. Each time you fail to finish, you lose a heart. It is not possible to play a level unless you have at least 1 heart.
Hearts can be gained in 3 ways:
- Purchasing a refill of hearts by using your coins.
- Waiting for a period of time until the hearts are filled automatically.
- Earning heart rewards by completing levels and challenges.