Math Poettary -- continuous, but not differentiable

     A few weeks ago I was introduced via email to Gauarav Bhatnagar, a mathematician now at Jawaharlal Nehru University in New Delhi, India.  In addition to varied and deep mathematical and educational interests, Bhatnagar likes to play with words; here are a couple examples of his poetic wordplay -- or, as he calls it, poettary.

        Continuous function     by Gaurav Bhatnagar

        A continuous function,
        draw it without
        picking up pencil
        from paper.

        At all points,
        the left hand limit 
        the same as
        the right hand limit,
        the same as
        the value of the function
        at the point.

        At all points
        its value
        what it should be.                                Math Poettary #3

                Not differentiable

                A continuous function
                Going along nicely
                without lifting pencil
                from paper.

               Ouch!
               This sharp point
               got me,
               its not differentiable.                         Math Poettary #4

More of Bhatnagar's "Math Poettary" is available at this link.