What is the difference between powder foundation and eyeshadow, besides the purpose and color?

Well foundation is formulated for skin while eyeshadow's formulated for your eyes so the texture and consistency is obviously different, powder foundation's thicker and it's molecules are closer together and the powder's smaller, eyeshadow spreads more easily and smudges eaiser, let's just say if I decided to put on skin coloured eyeshadow intead of my foundation I'd look like an umpa lumpa with the worlds biggest pores.