This year we wanted to make a pinewood derby car that looked like a Lamborghini Police car (POLIZIA). What's a police car without a lightbar. Built a small circuit using 555 timer chip and 2 Blue LED's. We needed a lighter to make the LED's diffuse and look like a police car. Enjoy. Here is link to 555 circuit we used: http://www.instructables.com/id/Flashing-LED-using-555-Timer/Printed with Translucent PLA at 0.2 mm layer height