This DS Lite Case is called the "Magic Puzzle Case", however, what it really is, is a 'sliding blocks puzzle'. There are 2 different 15-square puzzles built right into the exterior of this case. One with a CG Sonic portrait, the other with a CG Tails portrait. This type of puzzle has 1 blank square. You slide the pieces around, trying to arrange the image back to its original state, by only being able to move 1 block at a time. The case itself appears to be gray plastic.
This is the first of it's kind (a portable console case that is also a separate type of game) but it's also a little confusing, because if you have a DS available to play with, why would you want to choose to slide blocks instead? Maybe it's for when the battery runs down?