Earlier this week, Samsung announced Gear VR, a virtual reality headset that uses the company’s Galaxy Note 4 phone and software from Oculus VR. According to Oculus’ Chief Technical Officer John Carmack, getting that software to run on a mobile device was no easy task.

“There’s the normal hell of moving to a new platform—and I gotta say, Android was more hell to move to than most consoles I’ve adopted,” Carmack told Gamasutra in an interview. “Just because of the way Google has to position things across a diverse hardware spectrum, and because Google still doesn’t really endorse native code development—they’d still rather everyone worked in Java. And that’s a defensible position, but it’s certainly not what you want to be doing on a resource-constrained VR system. So brace yourself: Android setup and development really does suck. It’s no fun at all.”

According to Carmack, another challenge that surprised him was how important power management was not only to battery life, but performance. Taking full advantage of all four cores of the device’s CPU, he said, overheats it within minutes.

Carmack said that the plan at the moment is that the device will notify users as it’s about to overheat, giving them the option to either end the session there, or change to low-power settings if the game is capable of adapting to them.

“The power issue is going to be a big battle, and it’s going to be interesting to see because we don’t know yet how many people will like smaller nuggets of entertainment experiences instead of longer-form things,” Carmack said. “We’re hoping developers make a lot of short, bite-sized nuggets of entertainment because they work well on mobile—they don’t tax the thermal and power so much, and they also have another benefit: since we don’t have positional tracking on mobile, we know we’re going to cause problems for more sensitive people.”

One of the greatest things about a mobile VR device, Carmack said, is that it will make VR more approachable, allowing developers to easily demo their games or applications without having to carry around a PC. Carmack also noted that the Note 4 hardware is “way, way better than DK1.” However, he said that it will require a lot more optimization from game developers, Samsung, and mobile game engines like Unity and Unreal Engine 4.