There is! It's so cool - I've only seen videos for it and such on YouTube. But it's a branching path, choose-your-own adventure type game! You've got all these different routes you can take, and all these different endings! One of them even *gasp* ends happily for the girls, with all of them uniting to take out Walpurgisnacht without Madoka making a contract at all.

You can even get Mami, Kyoko, and Homura turned into witches if you play your cards wrong. They made actual witch forms for them. And it was creepy as fuck. Mami's familiars are dolls of Kyoko and Madoka.