It may also be possible to identify specific situations where
the difference between two users is sufficiently dramatic, so
that login is no longer necessary and a persistent general
classifier can be used. One example application scenario is
differentiation between parents and children, or teacher and
young student, where games and educational experiences
may be designed according to who is providing input. For
example, in an educational application a teacher could draw
a hint to help a student solve a math problem; the hint then
would fade out after a few seconds, prompting the student
to complete the problem him or herself.