There are so many rules for a Disney princess. Too many for Disney’s newest princess, the Scottish heroine Merida in “Brave,” to remember.

“A princess does not doodle,” her mother lectures in a light Scottish burr. “A princess does not chortle.”

“A princess does not stuff her gob.”

“A princess does not raise her voice.”

But here’s the one that makes the fiery redheaded archer snap:

“A princess should not have weapons.”

Pixar’s first “Disney princess” completes the evolution of the studio’s distinctly American take on young womanhood. Princesses have evolved from sailor-obsessed mermaids to Merida, a spunky, self-assured lass who’d rather eat an arrow than take up with some guy her parents point her way. She has duties, obligations, an arranged marriage to endure. Her mother, Queen Elinor (voiced by Emma Thompson), may insist “We can’t just run away from who we are.”

But as Merida narrates, her fate should be her own.

“Destiny - it’s the one thing we search for, or fight to change.”

“Brave” is a spirited Scottish-accented romp that packs female empowerment into a generally amusing tale of youthful impulsiveness and its consequences. The writers and animators blend the oafish, brawny Scots humor of “How to Train Your Dragon” with the magic of “The Secret of Kells” into a story about being brave enough to change your fate.

Merida (Kelly Macdonald of “Nanny McPhee” and “No Country for Old Men”) seizes her destiny when her father (Billy Connolly) and mom start parading unsuitable suitors before her, a marriage that will keep the peace among the Scottish clans. As tradition would have it, the would-be-kings compete in feats of strength to win her hand. But she selects one sport where she herself dominates. She hopes to win her independence with the draw of a bow.

Since its inception, no animation house has been as good at telling an adult story for children, as adept at tugging the heartstrings as Pixar, and “Brave” continues that tradition. The colors are stunning, the animation lush, photo-realistic and wet. And if they haven’t progressed as far as some in animating the human face, that’s just as well. Princesses are supposed to look otherworldly.

It’s the destiny of Pixarvto change the way movies, and the way wide-eyed young viewers look at “princesses” from now on. They’re beautiful, yes. They’re also smart, self-reliant and able to learn from their mistakes, as long as they’re the ones who get to make those mistakes in the first place.