The surprise hit of Google I/O was without a doubt Cardboard. Google’s paper product — or phone-based VR viewer — made its debut during yesterday’s keynote, and today, David Coz, the project’s founder, revealed its origins.

Depending on who you ask at I/O, Google went ahead with this project either because it wanted to show that Facebook overpaid for Oculus Rift or because it is jealous that it couldn’t acquire it. According to Coz, however, who works for Google’s Cultural Institute in Paris, Cardboard was simply a project he felt like working on.

“I’m a big VR fan,” he said, adding that there has been so much progress in this space in the last few years. With Cardboard, he wanted to see how he could build a VR viewer in the “simplest and cheapest way.”

The project started about six months ago. After Coz showed it to Google Research scientist Christian Plagemann in Mountain View, it became his 20 percent project, and the company decided to go ahead with it for a larger project.

So why use cardboard? Coz said he started working with it because it was an easy way to hack together a prototype, but he also liked it because he wanted the viewer to look really simple. All the processing, after all, is handled by the phone. In addition, he noted that Google wants anybody “to just take scissors and staplers and modify it.”

Given that Google has made a developer toolkit available for Cardboard and that the paperhardware is not just simple but also open source, chances are we will actually see quite a few Cardboard-based apps and viewers from other manufacturers in the near future. The team also talked a bit about how Google’s Project Tango could be used for more precise head tracking.

To be fair, others have tried a similar approach to phone-based VR viewers. None of them, however, can match Google’s reach and existing developer ecosystem.