When Nintendo first began work on the follow-up system to the DS, 3D visuals weren't part of the plan.
It wasn't until after 2008 that Nintendo considered using 3D in games once again, Nintendo 3DS project head Hideki Konno told Japanese magazine Famitsu (translated by Andriasang).
Planning for the successor to the DS began when the original DS was completed (it launched in Japan in December 2004), so by the time Konno joined the project, Nintendo already had prototypes which would serve as the basis for the 3DS.
The initial target, Konno reveals, was to make a new system that was backwards compatible. This meant it had to retain the two screens and bottom screen being a touch pad of the DS.
When Konno joined the project, he began to think about 3D. His initial tests involved connecting a 3D LDC panel to a Wii so he could see if Wii software could be made into 3D.
Konno found playing Mario Kart Wii on a naked-eye 3D panel to be "very nice". Various related parties gathered to see this demo and were impressed. These early demonstrations also consisted of 3D figures of Mario and Luigi, which also impressed viewers.
Meanwhile, those familiar with the upcoming handheld know that the 3D visuals can be turned up and down with a slider, but it wasn't always so.
The "volume control" went through numerous ideas, including plus and minus buttons and options settings at the software level, before the slider control was decided upon.
The 3D Mario Kart Wii demo is what lead to the final slider form. They tested out the Mario Kart demo with an analogue volume switch and found the feel of the game world changing in real time to be unique.
The Nintendo 3DS launches in Japan on 26th February, and in Europe on 25th March. UK shops are selling it for just under £200.