"The world of Lego is safe by its nature," Smith tells us, as we see our first Dementor. "So it's impossible for anything to be scary." Characters can fall apart and you can fail at certain tasks, but everything in the game is designed to keep you engaged and having fun. In an early level we smash up Gringotts Wizarding Bank to find hidden objects, and he notes that adults play this scene and become nervous. The idea of bringing that level of chaos to what should be an ordered place makes them uncomfortable. "Children, of course, have no issue with it," he says with a grin.

"In the Lego world, they are there to let you have fun," he says about the characters in the bank.

You can tell someone cares about their games when they get excited about a small detail. "Check this out," Jonathan Smith, the head of production at TT Games, said, showing off one of the 140 playable characters in Lego Harry Potter. It was a dog, and his ears moved up and down when he jumped. Smith was inordinately proud of the detail, and showed some more of the character's very dog-like animations. "Fang is the best," he gushed.

The important thing is that eventually, Fang plays dead. He can chase his own tail. These things may not impact the gameplay, but all the little details that fill the game and the world it exists in shows the level of commitment there is to the idea of fun. These two properties work well together, and our thirty-minute demo has us very excited for the final product.