it was
world usability day two days ago.

and there was some some event in yokohama, japan.
just then, i was searching about usability
the primary notion of usability is that an object designed with the users' psychology and physiology in mind are, for example:
* more efficient to use—it takes less time to accomplish a particular task
* easier to learn—operation can be learned by observing the object
* more satisfying to use
and there are some definition of usability,
then, i have to apply it to my project... but it's not easy...