Zuckerberg faced hours of tough, public questioning about where Oculus obtained its ideas and how much he knew about the startup when Facebook bought it for $2 billion.

Videogame publisher ZeniMax has been suing Oculus since 2014, claiming it unlawfully used its intellectual property to develop the virtual reality system that includes the Rift headset.

During one heated exchange with ZeniMax lawyer Tony Sammi, Zuckerberg told a jury that the technology was not even fully formed when Facebook bought the company.

"Improving on that technology doesn't make it yours If you steal my bike, paint it and put a bell on it, does that make it your bike," snapped Sammi at Zuckerberg.

Zuckerberg answered "no... but the idea that Oculus technology is based on someone else's is just wrong".

The Oculus acquisition was more expensive than the $2 billion price tag, Zuckerberg told the court. Apparently, it cost $700 million to retain employees and $300 million in pay-outs for reaching milestones. Oculus originally wanted $4 billion.

At the time, Zuckerberg testified, he was not aware of any theft claims against Oculus.

"It's pretty common when you announce a big deal that people just come out of the woodwork and claim they own some part of the deal," Zuckerberg said.

The Oculus lawsuit, in the sixth day of a jury trial, relates in part to programmer John Carmack who worked for id Software before that company was acquired by ZeniMax. He is now the chief technology officer at Oculus.

Zuckerberg denied that Carmack has unfairly used computer code from his previous position. "There is no shared code in what we do," he said.