CSS @media option not working correctly

CSS @media option not working correctly

I am trying to implement the CSS @media option but I am experiencing some
issues. I have three options, landscape, portrait, and mobile. The mobile
only activates vertically but horizontally it doesn't activate (basically
get the landscape option).
Here is the CSS:
@media (orientation:landscape)
{
some css
}
@media (orientation:portrait)
{
some more css
}
@media mobile
{
more css
basically the same as vertical
}
How do I do this properly? I want my mobile option to be the same as my
portrait option.
Thanks, Nat