Project Spark, Microsoft Studios game that lets players "build whatever" they want, broke any expectations the team had for how people would use it, studio manager Saxs Persson told Polygon.

In Project Spark, players can open a blank slate, craft their own terrain, program objects to behave specific ways and more. Speaking with us during PAX Prime 2013, Persson explained that as soon as the team began playtesting Project Spark, how people used the game surprised them.

"We thought we had foresight, until people started building, and then we had no foresight," Persson said. "People have an appetite for coming up with new mechanics and showing us things we never thought about. "

Persson said that while the team expected players to use the game to tell their own stories, they didn't realize how far their interest would extend. In one of the more impressive displays Persson has seen, a user created a tribute to Miami Vice, complete with car chases and boat explosions. Every time the team playtest, Persson said, they see something new.

"We needed to support multiple screens."

Playtesting is done through a combination of traditional methods and internal game jams, Persson said. Every three weeks, participating team members meet, compete and create something new. The changes made to Project Spark as a result are highly varied, but Persson says the biggest deviation is the team's decision to move from a console-only title.

"We realized that people wanted to sit and doodle with the game, and that generally didn't happen when they had access to the big screen in the house," Persson said. "While they wanted to play the game on the TV, they wanted to tinker on the tablet, and they wanted to continue on their laptop. We needed to support multiple screens."

From there, Persson said, adding a touch-based element on applicable devices was a natural next move. And though Project Spark will be a complete experience when it launches next year, it's hard to think of the game as ever truly finished.

"I can't imagine it," Persson said. "I don't think anybody on the team can imagine it. In our wildest dreams, we have I don't know, 10 years of development. But will it be complete enough in and of itself? Sure. But there's always something new."