We're calling it the "Treasure Mushroom". Use the multi-touch to knock the piñata, then collect the treasures that are hidden inside!
It's a great way to give the player a random reward without resorting to a gambling metaphor like a roulette wheel or slot machine.
What makes a good mini-game?I'm a big believer in the so called "Rational Game Design" approach. In particular, the variety matrix. It suggests you can break down your game into a number of axes, such as time-pressure, activity, space modifier, etc.
It then provides a recipe for combining those axes into novel variations. This aids the game designer's evaluation process and helps find the combinations which work the best.
Under this framework, the mini-game is part of "exotic gameplay". It changes the pace of the game by giving the player a new challenge, or a much needed break.
The mini-game must also be very easy to learn, and never punish the player, only reward.
Lastly, your mini-game must remain thematically similar to your main game. In "ScooterBoy", both the main-game and the mini-game have 'collecting' as a central theme.
What's your favourite/least-favourite mini games? Why not let me know in the comments below?