Firefly is a set of comprehensive software tools dedicated to bridging the gap between Grasshopper (a free visual parametric modelling plug-in for Rhino) and the Arduino micro-controller. This allows designers to tweak, experiment and control in realtime various elements of design with cheap and widely available devices like Nintendo's Wii Nunchuk controller or Parallax's PING ultrasonic sensor which provides a very low-cost and easy method of distance measurement.