What are stars used for and where do I get them?

Once you complete a puzzle in-game, you get money and a star as your reward. Stars are used to complete tasks in your to-do list and it's needed to renovate your mansion. You can know how much stars you have by looking at the upper right side of the screen.

You can stock up on stars by beating puzzles. This is the only way for you to get stars, you cannot purchase them directly in the bank. As long as you have enough lives, you can continue playing puzzles to get rewards.