The Legend of Zelda: Breath of the Wild has been praised in previews and impressions for its open systems, in which players can use multiple different methods to solve puzzles. This departure from the The Legend of Zelda franchise’s rote use of items — how every dungeon was always solved with a specific tool — was helped along by a creative prototype created by the Breath of the Wild team.

Game director Hidemaro Fujibayashi revealed a 2D Zelda prototype that mimicked concepts now seen in Breath of the Wild. He told a packed panel at the Game Developers Conference today that the prototype was useful for testing ideas of open-world gameplay, and also help the game return to its roots.

“I wanted to create a game where the user could truly experience freedom in this play field, and a sense of adventure again and again, as they freely navigate through it,” Fujibayashi said through translator. “When I started to think this way, the NES Zelda came to mind. Every time the screen scrolled, there was a new discovery to be made.”

To recapture that idea — the “essence,” as Fujibayashi called it — he wanted to change the game from a “passive” game to an “active” one. Those active game experiences, in Fujibayashi’s mind, included having puzzles that didn’t just have one solution, and objects that could react with each other in multiple ways. Before he decided to test this in the more complex systems of a 3D Zelda world, he enlisted Breath of the Wild technical director Takuhiro Dohta to build a 2D prototype that included pieces of the game’s physics and chemistry systems.

A small slice of that prototype was shown off during the GDC talk, with comparison shots of how its creation impacted Breath of the Wild’s puzzles.

The quickest way to bring these ideas to life, and present it to the team, a 2D prototype of #Zelda was created. pic.twitter.com/OJnE4yt8Oi — Nintendo of America (@NintendoAmerica) March 1, 2017

The prototype didn’t include any puzzles. It was just a situation, and a goal, and Fujibayashi said it created many challenges to solving it.

“When the players have diverse actions, items, and choices, an active game was created, where a user can freely create solutions,” he said. “Through this simple, primitive experimentation, we made the call of what to change and what not to change to complete the game design.”

While it’s unlikely players will ever be able to play with this detailed prototype, it certainly could be used to inspire other projects down the line.

The Legend of Zelda: Breath of the Wild comes to the Nintendo Switch and Wii U on March 3.