Instructions: click and hold on a box, let go on the number of your choice and that will fill the square. Try to solve all 256!
A true Base 4 sudoku could be 16 layers of this, and you would have to worry about the z dimension as well. This is just a slice of the true base 4 experience.
EDIT: I was mistaken^: base 3 sudoku is only 2d, so base 4 sudoku would be 2d as well. I just like the idea of 3d sudoku...