Style guide: tristatecheckbox

The below definition conflicts with itself.
If the item is partially checked, space rotates through checked, unchecked 
and then partially checked again.
However, the first bullet says if it's not checked that space  checks it! 

Is the implementation supposed to have 2 different code paths for 
unchecked checkboxes depending on whether it was originally partially 
checked?

- Aaron

Three State Check Box
If not checked, space checks the check box
If checked, space unchecks the check box
If partially checked, space will rotate through checked, unchecked, and 
partially checked states.