When Nintendo started work on their successor to the Nintendo DS, a 3D screen wasn’t part of their plan. During a Game Developer’s Conference panel, Hideki Konno, Manager of Nintendo’s EAD group, said his own team was reluctant. Kenichi Sugino who helped design the ill-fated Virtual Boy was one of the most skeptical members.

Konno decided to test the concept before moving forward. He and the hardware staff developed a 3D enabled Wii. A special version of Mario Kart Wii was developed to demonstrate what 3D games could be like.

After Konno settled on a 3D screen, the team began working on a depth slider. This volume-like control allows users to add or subtract depth, which magnifies or diminishes the strength of the 3D effects. Along with hardware, software was created to make this feature possible. The very first 3D depth slider was also for Wii. Nintendo staff mounted a depth slider to a nunchuck to test it out.

Nintendo, Konno explained, tested out the crosspad by experimenting with different springs. While Nintendo settled on components, the team wasn’t sure where to place the Slide Pad (analog stick) on the next handheld. Should the analog stick fit on the top of or below the D-pad?

A 3D version of Super Mario 64 DS was created along with a special Nintendo DS with interchangeable control pods. Players could put the Slide Pad in its final position (on top of the D-pad) or on the bottom.

Like the 3D enabled Wii, this Nintendo DS "phat" pictured above will not be sold in stores.