Suggestions for robotic cat toy

I’m considering DIYing a small robotic toy for my cats. I would like a robotic platform that is…

  1. inexpensive (preferably under $100);
  2. robust (if it works, the cats will bat it around);
  3. small (so they CAN bat it around);
  4. programmable (so I can modify the behavior); and
  5. able to deal with changes in orientation (keeps working when they flip it over)

Any thoughts about Pololu products, or other products, that I should consider?