Playing with Lothar Collatz conjecture, also called 3n + 1 conjecture, can be interesting to generate some constant random things a simple way. Was funny to create an interactive graphic representation of a function with values displayed at several places, a convenient way.
Display: step to reach end loop/division of graph height to fit view
* left/right arrows keys to increase/decrease values/view
* button(z) to generate new random number seed.
# up down arrow or left mouse button + up down for zooming vertical view of graph