Keyboard 3x3, by the first pressing we select one of 8 zones, by the second pressing we select one of 8 buttons.
In the slide version, we leave the center in one of 8 zones, and return to the center from one of 8 sides.
Demo: sudaku.html
suDAku Rubik's: rubik
Wii Nunchuk: wii-nunchuk
Keyboard Layout Editor: suDAku