In the latest Iwata Asks feature, Nintendo shared a pair of prototypes for the upcoming 3DS console today, including one with customisable input positions.
The new console's layout and feel is set in stone until the obligatory lighter/smaller versions, but to get to this point Nintendo's research team had been hard at work with prototypes made to discuss and agree on button placement, screen sizing and more.
One of the big issues was where to place the Circle Pad and the regular D-pad. Above or below? Nintendo even had a working unit that allowed the two to be swapped like ickle LEGO blocks. Nintendo even joked about including that as a feature in the retail version.
After many revisions, decisions and even stamping on prototypes, the final hardware was ready to be massed produced in time for the worldwide February/March release.